chapter 2 - walking

7/31/2019 Chapter 2 - Walking

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2C HA P T E R

13

Walking

BackgroundWe are all pedestrians; any trip by any means includes at least asmall distance covered on foot at the beginning and end of eachjourney. Walking is the basic urban transportation mode that has

allowed settlements and cities to operate for thousands of years.It is still very much with us, but its role has been eroded with theintroduction of mechanical means of transportation, drastically soin American communities, with the dominant presence of the pri-vate automobile in the last half century.

The principal transportation mode in the developing world,even in large cities, is still walking because of constraints on theresources needed to operate extensive transit systems. Peoplecover long distances on foot every day and expend human energythat they can scarcely spare. Walking under those conditions is an

unavoidable chore that consumes productive capability. In NorthAmerica and Western Europe, the attitude and policies are justthe opposite: walking is efficient, healthful, and natural. Weshould do more of italmost everybody agreesand some of thecurrent trends should be reversed. Ironically, among the mostpopular exercise machines in health clubs and in homes are tread-mills that simulate walking, which could be otherwise accom-plished with a transport purpose on the street.

Source: Urban Transportation Systems

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14 Urban Transportation Systems

Admittedly, because of the size of contemporary metropolitanareas, with origin and destination points far apart, the need tosave time consumed in routine travel, and the desire for basic

comfort and avoidance of severe weather conditions, walking asa transportation mode has limitations. But the niche that it canfill is still rather large, and the opportunities are by no meansfully exploited. Just the reverse is happening today, and someproactive programs will be necessary to restore reasonable bal-ance.

The trend in the percentage of commuters who walk to work inthe United States1 has been negative:

1960 9.9 percent

1970 7.4 percent

1980 5.6 percent

1990 3.9 percent

19992 3.1 percent

Much of this can be explained by the fact that land use pat-terns have become more coarse-grained (i.e., greater segregationof job places and commercial activities from residences), andtrips have become longer overall, but there is also the greaterpropensity to use the car for any purpose, even just to go around

the corner. Working at home has increased slightly, but notenough by far to explain the drop in walking to and from work-places. Appeals to reason and civic responsibility will not alterthe prevailing attitudes much; programs to make walking attrac-tive to individuals will have to be expanded and implemented.The contemporary built environment in North America is notalways fully enabling toward pedestrians. Not all new streetshave sidewalks, they are not always structured into coherent net-works, and they frequently lack proper amenities (good pave-ment, lighting, rest areas, etc.).

1 U.S. Census data.2 Since the 2000 U.S. Census data were not yet available, information from the

American Household Survey was used for 1999.

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Walking 15

Development History

The historical review of walking could begin some 20 millionyears ago, when certain animalsour ancestorsstarted to movearound on their hind legs.3 That would not be a very profitablediscussion; even the last 6000 years (save the last 150 years orso) can be quickly summarized to arrive at the conditions that

prevail today.For thousands of years, settlements and urban groupings,

eventually evolving into cities, were almost entirely walking envi-ronments. Some deliveries were made by pack animals and carts,some people were carried by one device or another, and soldiersand chiefs liked to ride, but most movement and linkages insidecities were accomplished on foot, even the carrying of heavy bun-dles and parcels. Cities had to be of a walking scale, and theywerealmost all of them could be easily traversed on foot withina quarter of an hour. Even the few very large ones (imperial Rome,Beijing, Paris, London) were assemblages of neighborhoods thateach contained the daily life of the residents, including theirworkplaces. Extensive wheeled and animal traffic, however, waspresent in the larger cities as a part of production and distributionactivities. Street congestion on the narrow streets was knowneven in ancient cities.

The streets, often just the linear spaces left between buildinglines, usually made no provisions for separate types of movement.People, carts, and animals used the same channels, mixed freely,and were all impeded by the many activities that spilled out on thestreet and have traditionally been a part of the urban scene: ped-

3 Needless to say, any dates with prehominid hominoids are uncertain. Progresswas slow and gradual, and new archaeological discoveries are always making

adjustments to the dates. The evolution toward erect locomotion apparently is

not yet quite complete either, judging from the fact that many of us tend to getchronic back pain.

What is a featherless biped?

A plucked chicken or a pedestrian.What is a pedestrian?

A driver who has found a parking space.

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dlers, vendors of food, purveyors of various services, entertainers,musicians, preachers, children, thieves, and beggars. Dependingon the organizational level of any society and the attention paid to

public works by any city administration, the streets may havebeen paved,4 but usually were not (except for major avenues), andthere may have been provisions for drainage, which can be seeneven in some of the very ancient cities. Principal streets in thecities of Mesopotamia and the Indus Valley show evidence ofdrains and pedestrian lanes. Significant Roman cities providedraised sidewalks along both sides of the street, leading to adjoin-ing store and housing entrances. There were stepping stonesacross the vehicle channels, spaced to allow carts with wheels astandard distance apart to move along.

Yet, the practice of providing sidewalks became lost for manyhundreds of years. Water and liquids found their own way, notinfrequently turning street surfaces into malodorous and pestilentbogs. European cities, as a rule, had no sidewalks during themedieval and Renaissance periods; they appeared in the secondhalf of the eighteenth century, at least in the more prominentcities.5 Available evidence indicates that walking on urbanstreets, up to the Age of Enlightenment, was a dangerous anddirty practice. Despite certain images based on romantic nostal-gia, people walked when they had to, but not for pleasure and

recreation. That became possible only considerably later, whensome protected and designated spaces were developed andopened to the publicpromenades, public gardens, and parks.

In the nineteenth century, sidewalks were always presentalong the sides of improved streets, with a curb and a gutter, inall the cities of the Old World, as well as in colonial towns. Theprime pedestrian environments were the grand boulevards, not inParis alone.6 In American cities, the nineteenth-century park-ways in their early form extended the landscaped park environ-ment into the city itself and were intended for leisurely strolls and

carriage rides.

4Paving means that a reasonably watertight surface is created that will keep itsshape with no ruts under the pressure of wheels, hooves, and feet, and that

there will be little dust during dry periods and no mud on wet days.5 This is a conclusion drawn from scanning many contemporary images of cities,assuming that they are reliable in the details.6 See J. Cigliano and S. B. Landau (eds.), The Grand American Avenue:

18501920 (Pomegranate Artbooks, 1994, 389 pp.).

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Walking 17

The functional purpose of a sidewalk and a curbwas to protect pedestrians from the consequencesof horse-drawn wheeled traffic, which had grown

immensely in volume and impact. Crossing majorstreets became a dangerous adventure, horses andheavy wagons were frightening to most people,andmost importantsanitary conditions on thestreets were abysmal. Litter and garbage were notcollected with particular diligence, nor was theexcrement of hundreds of horses. On a wet day,ankle-deep slurry covered street surfaces, as it hasbeen described by some earthy contemporaryauthors. With a raised sidewalk in place, the tides

could be held back, a reasonably solid surfacecould be provided, the adjoining property ownerscould at least sweep their own frontages, and somepositive drainage could be achieved. Nevertheless,a gentleman escorting a lady was expected to walkon the curb side to shield her from likely splashes.Gallantry aside, it was presumably easier to cleana pair of trousers than multiple voluminous andfrilly skirts.

A specific building form favorable to pedestrians

was the arcade, colonade, orloggia along the street fronts of build-ings. They are encountered in various historical periods at manylocations. They were built primarily to gain more space on theupper floors by protruding into the street, but they also offeredthereby a sheltered path for walkers (provided that the arcadeswere not cluttered up with other activities), since wagons and cartscould not conveniently enter. In very hot climates and in placeswith extreme rainfall, they are a practical means of minimizing thedisruptions of urban life. Unfortunately, today, in crime-proneAmerican cities, street-front arcades are sometimes banned

because of the fear that muggers may hide in their shadows.Another similar device was thepassage orgalleria (also called

an arcade in American English)a building perpendicular to thestreet that provides accommodation for many stores on a single ormultiple levels, with an open central circulation space. The firstof these probably was the Galleries de Bois in Paris, opened in1786. The most famous one is the Galleria Vittorio Emanuele IinMilan (1865), but there are many others throughout Europe

Covered sidewalk in a Renaissance city

(Vicenza, Italy).

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practically in every large city, since they were seenas prestigious retail venues in the nineteenth cen-tury. America has its surviving examples as well

in Cleveland, Providence, and Los Angeles. Thisconcept has emerged again in todays planning forpedestrian spaces, as is discussed subsequently.

In the second half of the nineteenth century, themovement toward park creation in American citiesresulted in attractive walking environments aswell, but for recreational purposes only. The CityBeautiful efforts in the very early twentieth centuryextended the concept of formal boulevards, withlandscaped walkways, enhancing the prestige of

any city at that time.The appearance of modern architecture somedecades later brought with it new concepts inpedestrian space. For the purposes of this discus-sion, the principal characteristic was the separa-tion of pedestrian walkways from vehicular traffic,which by that time had become a threat to safetyand, due to its speed, incompatible with the paceof human locomotion. The results weresuperblocks(towers in a park), with motor vehicles kept on the

periphery and pedestrians able to follow separated paths. Le Cor-busierperhaps the most influential architect of the twentiethcenturywas a principal proponent of this design form throughhis many conceptual plans and several projects that were imple-mented, starting in the 1920s. Independent walkways were notexactly a completely original idea, but they were brought into thecity fabric as a major design-governing feature. Superblocks wereadvocated for lower-density neighborhoods as well (for example,Radburn, New Jersey, in 1929). Not all the efforts were attractiveor successful (for example, the massive and monotonous public

housing projects in large cities), and frequently problems withmaintenance, policing, and privacy came to the fore.

Nevertheless, the separated pedestrian walkway at the locallevel leading to service facilities, institutions, and transit stopsremains a strong concept in the inventory of planning and designoptions. Within the last few decades, however, a differentapproach has also emerged under the label ofnew urbanism (orthe neotraditional planning, pedestrian precinct, ortransit village

Multistory nineteenth-century arcade in Cleve-

land, Ohio.

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Walking 19

concept), which attempts to restore primacy to pedestrians withinresidential and commercial districts.7 It recognizes that motorvehicles create conflicts, but, instead of seeking to segregate peo-

ple in safe environments, asserts that automobiles should bemade to behave and that streets should accommodate all move-ment, particularly walking, with no interference or dangers. Thestreet traditionally serves all; there should be no reasons to drivefast or irresponsibly, and, by creating reasonably high densitiesand clustering activities, most destinations should be accessibleon foot. Whether residents living in these districts do actuallyalways walk and whether developers will embrace the conceptand will be able to create a mass market remains to be seen. Thenew urbanists also believe that contemporary city folk want to

recapture a sense of belonging to a community and basic neigh-borliness through walking to accomplish daily chores and sittingon a traditional front porch facing the public street. The intent isto be applauded; social scientists, however, continue to record agrowing deliberate alienation by most residents from the publicrealm and a retreat into their own private spaces (in the enclosedcar and in front of the TV set).

Similar community-building aims are expressed under trafficcalming programs as approaches toward a safe and attractivepedestrian environment, which are outlined further in Chap. 5,

Automobiles.No discussion of pedestrianization in the United States can

avoid suburban shopping centers. This purely American buildingform has at its core the presence of a pedestrian spacedeliber-ately designed to attract people, make them linger, and encouragespending. While these service clusters may be almost impossibleto get to on foot in low-density suburbia, once the customers parkthe car, everything that has been learned about keeping peoplehappy and comfortable is applied here, deliberately and throughcountless repetitions. This encompasses weather-protected space

(usually enclosed, always at the same temperature), widths of cor-ridors that allow show windows on both sides to be seen, plentyof sitting and rest areas out of the main flow, colorful (if some-

7 Much literature has been generated recently regarding this concept. See A.Duany and E. Plater-Zyberk, Towns and Town-Making Principles (Rizzoli, 1991,

119 pp.) and P. Calthorpe and W. Fulton, The Regional City (Island Press, 2001,

304 pp.).

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times garish) dcor with historical or popular design referencesthat are easily understood, food courts that provide for all tastesand keep customers on the premises, no interference by (not even

visibility of) goods and maintenance operations, sufficient escala-tors and elevators if operations take place on several levels, exem-plary cleanliness, and complete security.

The ancestry of American shopping malls can be traced back tothe first half of the twentieth century, to a few examples of clus-tered stores in model developments (Roland Park, for example, inBaltimore), and particularly to the Country Club Plaza in KansasCity (1922) as the first automobile-oriented center. The realmodel, however, was more likely the series of farmers marketsbuilt in Los Angeles in the 1930s, with off-street parking lots and

central pedestrian circulation areas. A few shopping mallsappeared before World War II, but the real boom started in the1950s, accompanying the explosive trends of suburbanizationand movement of families to open peripheral territories. Thou-sands were built each year during the peak period in the 1960sand 1970s, reaching a total inventory of more than 26,000 mallsacross the country by 1990.8 The first regional mall was North-gate in Seattle (1950), followed by Northland in Detroit (1954).Since the 1960s, almost all the large malls have been enclosedand equipped with full climate control. The size records were

set by the West Edmonton Mall in Canada (3.8 million ft2

[350,000 m2] of retail space, 1981) and the Mall of Americaoutside Minneapolis (4.2 mil-lion ft2 [390,000 m2], 1992).

While shopping malls arenot specific transportation fa-cilities, they are the prime pop-ular examples of pedestrianenvironments in North Americatoday. They can be seen as lab-

oratories where human walking

Interior of a contemporary shopping mall in Newark, New Jersey.

8 See M. D. Beyard and W. P. OMara,Shopping Center Development Hand-

book (Urban Land Institute, 1999, 3d

ed.) and W. Rybczynski, City Life:Urban Expectations in a New World

(Scribner, 1995, 256 pp.), Chap. 9.

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Walking 21

behavior can be observed and conclusions reached as to whichfeatures are favored by real people and which are not, even if thefindings are not always encouraging. (The counteraction of old

city and village centers against shopping malls to recapture lostbusiness by rebuilding traditional commercial cores into pedes-trian-friendly environments is outlined under Automobile-Freeand Automobile-Restricted Zones in Chap. 5, Automobiles.)

Another approach toward expediting pedestrian operationsnot particularly new, eitherhas been the creation of several lev-els, thus giving crowds adequate space. The issues associatedwith multiple pedestrian levels are discussed on subsequent pages,but successful examples are found either as entire underground net-works or as connecting mezzanines under major street intersections.

Bringing pedestrians one level up is also a possibility, but the recordwith this idea is rather spotty. Efforts to do that in the core areasof London (Barbican), Stockholm, Bogota, San Juan, and otherplaces have largely not fulfilled expectations. Second-level sky-ways are an American invention, and they work well and arepopular as weather-protected connections in cold climatesbetween garages and commercial establishments.9 They arefound in MinneapolisSt. Paul, Rochester, and Cincinnati, and asshort linkages at many other places. While they can penetrateand enter buildings, they operate mostly as corridors, not so

much as shopping streets, and thus can be clearly classified ascomponents of the local transportation networks.

The situation is different with underground pedestrian sys-tems. While some of them take the form of interconnected corri-dors (as in Houston), they can accommodate activities along thesides. The most extensive network has been developed in Mon-treal, where spacious pedestrian passageways under the streetlevel connect many key buildings and transit access points. It istruly an underground system. Very large pedestrian networkshave been developed in the larger cities of Japan, as well as in

Seoul, Korea. Extensive, albeit smaller, arrangements are found inToronto and New York. The World Trade Center, for example, hadan extensive below-street environment with a large retail compo-

9 For a full analysis see K. A. Robertson, Pedestrian Walking Systems: Down-

towns Great Hope or Pathways to Ruin? Transportation Quarterly,July 1988,

pp. 457484.

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nent. It was about to be rebuilt and improvedbefore its destruction. In many instances, connec-tions from underground transit stations extend into

the surrounding blocks and offer direct entries tostores.Localized additions to the overall pedestrian sys-

tem in high-density districts are underground cross-ing mezzanines under major street intersections.The best examples are equipped with escalators,offer a wide inventory of convenience shopping andgrazing (fast food), have public toilets, and can evenbe effectively used for safe loitering. Vienna, Lon-don, and Prague, among other cities, have a number

of successful cases.To complete this review of options, mention hasto be made of contemporary enclosed commercialand activity spaces as a single building or combina-tion of buildings, as represented by enclosed urbanmalls. They are not transportation paths, althoughpedestrian movement crosses them, and they fre-quently offer attractive alternatives to the outdoorsidewalks. Indeed, the latter point can be regardedas a criticism, because they tend to siphon life

away from the traditional walkways. At this time it is hard tothink of any city, particularly in Europe, that would not have oneor more examples. The first such project in the United States wasthe Midtown Plaza in Rochester (1962), and the more visibleexamples today are the ZCMI Center in Salt Lake City, the Galleryin Philadelphia, Eaton Center in Toronto, the Embarcadero Centerin San Francisco, Peachtree Center in Atlanta, Water Tower Cen-ter in Chicago, and many more. There are also interesting projectsin converting historical buildings into such environments (forexample, the Old Post Office in Washington and the recently

refurbished Grand Central Terminal in New York).Besides examining physical improvements encompassing

pedestrian spaces and paths, there is the question of the extent towhich free human behavior, as represented by walking as arepeated daily activity by everybody, can be analyzed systemati-cally, provided for, and planned accurately through quantifiedmethods. For thousands of years, pedestrian spaces happened (afew were deliberately designed), and they either worked or they

Nicollet Transit Mall in Minneapolis, Min-

nesota, with walkways and skyways.

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Walking 23

didnt. If these environments had problems, they were progres-sively changed; i.e., they became adjusted to needs and expecta-tions over the years. Or they were scrapped. Planning and design

depended on the instincts, good sense, talent, and experience ofdesigners and builders. Layouts and dimensions were arrived atimpressionistically. Some great successes were thereby achieved,but in most cases a trial-and-error process ensued.

That situation has changed, at least to the extent that designand planning tools have been created that bring considerablespecificity and reliability to estimates of space needs and thestructuring of safe and efficient flow paths.10 No claims are to bemade that this will automatically produce superior designs, butany design can now be tested as to its functional adequacy and be

at least sized accordingly. The principal point is that the planningof pedestrian facilities (spaces, paths, stairs, and sidewalks) can besupported by documentable analyses, thus bringing much morereliability to a task that has otherwise uncertain dimensions.

Types of Walking PracticeThe behavior of human beings when they are in motion in publicspaces is affected by the purpose of such action for each individ-ual at any given time. As familiar as walking is to all of us, sev-

eral distinct situations can be identified.

Walking Briskly

This represents the need to move expeditiously from Point A toPoint B. The principal purpose is to overcome distance quickly,and to do this by mostly ignoring all distractions and not beingdiverted by other destination or action possibilities. The bestexample is going to work in the morning under time pressure toreach the desk, or attending any significant event with a precise

10 The seminal work was done by J. J. Fruin of the Port Authority of New York

and New Jersey (published as Pedestrian Planning and Design (Metropolitan

Association of Urban Designers and Environmental Planners [MAUDEP], 1971,113 pp.), later joined by G. Benz (several articles jointly with Fruin andPedes-

trian Time-Space Concept (Parsons Brinckerhoff Quade & Douglas, 1986). Sub-

sequently, other analysts have expanded this subfield, and it is now a regularcomponent of traffic engineering.

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starting time. The shortest time distance is chosen; safety on thepath and reliability do count, but aesthetics and human amenitiescan be largely ignored. The walker in a real hurry will slosh

through puddles, jump traffic signals, elbow others out of theway, avoid stairs, and take any possible shortcut to keep to astraight line. This is definitely a form of transportation, with thetrip characteristics easily identifiable (origin and destinationpoints, time, mode, purpose, etc.). The action is rational withinthe operational context, and it is predictable as to its execution.Volumes, levels of occupancy, and speeds on connecting pathsand within spaces along the way can be estimated, if the numberof trip ends associated with origin and destination points areknown. Sidewalk loading conditions and the utilization of spaces

can be calculated. This is the pedestrian equivalent of channeliz-ing motor traffic flow and building highway lanes (in conceptonly, needless to say). The precise pedestrian flow analysis meth-ods, outlined in following sections, are very much applicable tothis situation and give good results.

Meandering11

But we are not always in a rush. People employ their senses toenjoy the surroundings, to look at interesting things that catchtheir attention, to gawk at other people, and to be a part of the

street scene as they walk along. Yes, it is still movement fromPoint A to Point B, but not necessarily in a straight line and not ata constant speed. Indeed, this type of action embodies the attrac-tiveness of being in a city, and every opportunity should be takento enjoy the walk and be distracted. Walking should be an uncon-strained and positive experience, as long as we are not late for thenext appointment. How much time any such journey will take is afunction of the time available to the walker, the interest level ofthe surroundings, and weather conditions. In other words, this isnot a steady-state situation, not even for the same traveler on a

regular schedule, and the level of predictability regarding theexact path and time consumed decreases. If a designer lays out anexciting path for walking and meandering, will all of us move inthe same way and consume the same amount of time? Most likelynot. It is a dynamic and changing situationbuildings, spaces,

11 The English language offers a few other possible descriptors for this type of

locomotion: rambling, peregrinating, sauntering, orstrolling.

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not dominate. Space-time occu-pancy, however, can be defined,movement paths can be iden-

tified, and restful places andenclaves can be structured.Ratio-nality and understanding gainedfrom controlled previous and on-going research can be applied.The pedestrian situation is mostcomplex because people do notstay in marked lanes as cars do,and in many instances all threetypes of walking, as previously

outlined, will exist concurrently.To create any successful pe-destrian environment, ideas andoriginal concepts generated by

first-rate designers are still crucial. Nothing very good is likely tohappen without a creative spark, but beyond that plans do not haveto be guided by intuition alone. The range of promising possibilitiescan be narrowed effectively and pilot projects can be tested system-atically by applying the study techniques developed recently. Thedesign of pedestrian spaces, movement networks, and nodes of

convergence can benefit greatly from a rigorous analysis.

Reasons to Support Walking

Economy

The walking mode involves very little expense, either public or pri-vate. The paths themselves, usually sidewalks, are usually builttogether with normal street construction, and the specific expenseis rather minimal. On a local street, adding sidewalks to the other

cost items would account for only a small fraction of the total cost.The pavements can be of a rather light construction since they donot have to carry heavy loads; however, they have to be strongenough to support an occasional maintenance or service vehicle.Separate walkways that traverse parks and open spaces have to beable to accommodate police cruisers and service trucks.

Cost of operation is not a concept associated with the walkingmode. Each person is responsible for his or her own equipment

Central pedestrian street in Munich, Germany.

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Walking 27

(shoes, mostly), which do wear out, but it is a normal personalexpense. An interesting issue is the consumption of energy. A 155-lb (70-kg) person will burn 280 calories walking briskly for 1

hour

14

which is a benefit in an overfed society in need of exercise,but may be a significant consideration for undernourished popula-tions. Walking slowly, only half of that amount is consumed; climb-ing stairs doubles the energy expenditure as compared to normalwalking.

Health

As mentioned previously, an argument can be made that the obvi-ous health benefits of this, the most basic, form of exercise shouldconstitute a major reason to equip American communities with

the best possible walkway systems. This is a question of not onlyoffering a rich inventory of physical facilities, but also a matter ofstructuring districts so that walking is a logical modal choice, andthe experience is safe and attractive.

Availability

There is no need to wait for a transit vehicle or even to turn onthe ignition; the mode is always present and ready for use (withinreason). Most cities, particularly in the industrialized countries,have done quite a lot to make the sidewalk network navigable to

people with mobility impairments (curb cuts with ramps through-out), thus making the walkway system more free of obstacles touse than any other transportation mode.

Cognition

A pedestrian is in direct contact with the surrounding environ-ment. The act of walking is automatic and does not require delib-erate attention or even too much care to avoid obstacles anddangers. The senses and the mind can be employed to appreciatethe streetscape or the landscape and to pursue independent

thought.

Environmental Protection

Walking is the ultimate environmentally friendly transportationmode. (No need to worry about heat generated by bodies andevaporated perspiration.)

14Source: NutriStrategy Web page.

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Reasons to Exercise CautionWalking, as pleasant and advisable as it might be, is not an all-purpose transportation mode because there are functional limi-

tations.

Distance

The human animal does become tired, rather quickly. We alsohave an advanced brain that is constantly searching for the pathsof least resistance and seeks to conserve personal energy (other-wise known asself-preserving laziness). The question that has pre-occupied transportation planners for some time is the reasonablewalking range that people will accept, particularly Americans

well-known as car-obsessed individuals. The examples range fromsome motorists who will circle a shopping center parking lot end-lessly to find a space closest to the mall, to dedicated hikers whotake great pleasure in long and challenging walks. On-street park-ing spaces are deemed to be good only if they are within 200 to300 ft (60 to 90 m) of the door.

A specific planning concern is acceptable access distance totransit stations or stops on foot. The general consensus today isthat a quarter mile (1320 ft; 400 m) is a range within which justabout everybody will walk; within a half mile (2640 ft; 800 m),

the number of walkers may be cut by 25 or 50 percent; a few, butonly a few, will walk a mile to any destination or transfer point.Eighty percent of walking trips are less than 3000 ft (0.9 km). Itis a curious fact that residents of large cities are more likely toembrace walking than those living in smaller places. New Yorkersin particular tend to be at the top of this list. Commuters from thePort Authority Bus Terminal or any of the major rail stations willreadily walk 3000 ft or more to and from their Midtown offices.

Major events and festivities represent an exception to walkinglimitationsa mile is quite acceptable under those circumstances.

(Any National Football League game, by definition, is a majorevent.) Even school children are pampered in this country: mostschool districts have a rule that any pupil or student is entitled toa school bus pickup if he or she lives beyond a 1-mi radius.

Speed

A human being is not particularly fast. A regular walking pace is 15minutes to the mile, which may be extended to 20 minutes. Thistranslates into 4 or 3 mph (6.4 or 4.8 kph). For short distances,

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Walking 29

since walking does not involve a startup or terminal time loss, theslow pedestrian speed does not matter, but it becomes a factor withlonger trips. There are some athletes who can cover a mile in lessthan 4 minutes, but even that is only 15 mph (24 kph), hardlycomparable to any motorized mode. A very good marathon runnercan maintain a 13-mph speed. The best that any human being hasdone is 9.79 seconds in the 100-m dash (22.8 mph; 36.8 kph),which cannot be sustained for any distance, either.

Traffic engineers, who are responsible for adjusting traffic sig-nals so that there is enough time for every pedestrian to cross astreet, are particularly concerned with velocities over short dis-tances.15 The usual design assumption is 4 ft/s (1.2 m/s), or 2.7mph (4.4 kph), which accommodates almost everybody. Young

15 Chapter 11.6 in J. D. Edwards, Transportation Planning Handbook (Prentice

Hall/ITE, 1992), p. 396 ff.

Distances That Can Be Traveled in 30 Minutes

Mode Miles Kilometers

Pedestrian walking leisurely 1.5 2.4Pedestrian walking briskly 2 3.2

Race walker 4.5 7.2

Jogger 3 4.8

World-class runner 6.5 10.5

Bicycle at normal pace 5 8.0

Bicycle in 1-h race 15 24.0

Local bus in dense city traffic 3 4.8

Bus on suburban streets 8 13.0

Express bus (suburb to central business district) 15 24.0

Streetcar in mixed traffic 4 6.4

Light rail service 8 13.0Subway in regular service 12 19.5

Commuter rail in regular service 18 29.0

Regional express train 22 35.4

Metroliner 45 72.5

French TGV (train grande vitesse) 80 130

Private car in a badly congested city district 1 1.6

Private car moving at normal urban speed limit 12 19.3

Private car on an expressway at 55 mph 27 43.5

Indianapolis 500 race car 90 145.0

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people walk faster, and 5 ft/s (1.5 m/s), or 3.6 mph (5.8 kph),would be workable for them. However, with the presence of a sig-nificant number of elderly persons in the flow, 3 ft/s (0.9 m/s),

or 2.0 mph (3.3 kph) may be used.Some tentative studies suggest that Americans generally walkfaster than all other nationals, except the Japanese. Also, that res-idents of the larger cities are more in a hurry, especially in Bostonand New York, than in smaller places. This is an intriguinghypothesis, which should be tested further.

Change in Elevation

People are reluctant to change elevations, because we know instinc-tively that this involves significant energy expenditure, as com-

pared to level walking. Thus, in any pedestrian designs for sizeableflow conditions, this aspect requires particular attention. Changesin level should be avoided if at all possible; mildly sloping rampsthat are not particularly prominent visually, escalators, or elevatorshave to be provided. There is a natural reluctance to use overpassesand underpasses (the latter also because of safety reasons).

Weather Condit ions

Adverse weather, whether it is rain, snow, high wind, or broiling

sun, will reduce considerably any propensity for walking. This isone of the principal reasons why indoor pedestrian environmentshave been so successful. In almost all climatic regions, however,any outdoor pedestrian space or path can benefit from full or par-tial shelters, particularly because walking trips will otherwiseshift to motorized modes at certain times, thus either overloadingtransit systems or requiring them to have standby capacity. Inmost instances deciduous trees are suitable additions since theirleaves provide shade, but their bare branches let the sun pene-trate in the cold months when some warmth is welcome.

Carrying Goods

Again, pedestrians have limitations, including how much weightthey are able or willing to carry with them. Briefcases and pocketbooks are one thing, but even shopping bags may present prob-lems. Being accompanied by small children or pushing strollersare not exactly encumbrances, but such common situations dorequire attention in the design of walkways.

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Walking 31

Impaired Personal Mobility

Any community has a certain percentage of people who havelarger or smaller disabilities that will reduce the extent of their

participation in the walking mode. These may be temporary, suchas a sprained ankle, or they may be permanent, such as missinglimbs. There are always the very young and the very old. The taskin the design of pedestrian facilities is to achieve accessibility thatallows the greatest percentage of the population to use them.Methods range from curb cuts at intersections that allow wheel-chairs to move, to audible traffic signals that assist those withvisual impairments.

Safety and Security

The technical term pedestrianvehicle conflict refers to the one-sided violent encounter between the soft tissues of a human bodyand a large, hard, frequently fast-moving, invulnerable metalobject. There are no air bags or other protective devices for thewalker; the only safeguards are to stay out of the way and toensure that motorists recognize the presence of pedestrians andknow that people always have priority in traffic channels whensafety issues are concerned.16

In the United States, pedestrian accident rates are consider-ably lower than those in most other countries, but this may sim-ply be due to the fact that fewer people walk here. The rates aretoo high nevertheless, no matter what they may actually be. Thisis a national concern, particularly if walking and jogging are to beencouraged as an overall policy, and programs have been devel-oped both to educate and instruct drivers and walkers and to pro-vide physical safety elements that would minimize, if notpreclude, such occurrences. There were 5307 pedestrians killedin 1997, which represents a 43 percent decrease in the rate per100,000 population since 1975. During this period, 13 to 17percent of all victims of fatal accidents associated with motorvehicles were pedestrians.17 By 2000, the fatalities haddecreased further to 4739. The largest causes were walking,

16A reasonably complete summary of pedestrian safety issues and programs is

found in J. L. Pline, Traffic Engineering Handbook (Prentice Hall/ITE, 1992), p.

19 ff.17 U.S. Department of Transportation, Fatality Analysis Reporting System.

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playing, or working in roadway and improper crossing of road-way at intersection.

Unfortunate associated issues are that many people do not

observe traffic regulations scrupulously when walking, andenforcement frequently tends to be rather lax with respect topedestrian behavior. There are places where local residents havea rather cavalier attitude toward minor regulations and will jay-walk and ignore Walk/Dont Walk signals (New York, Paris, andBangkok come to mind),18 leaving aside the general urban situa-tion in Third World cities where traffic and crossing conditionscan be quite chaotic. There are other locationsprimarily inWestern Europe and Japanwhere rules are respected diligently.All this argues for the implementation of hard control devices

(barriers, for example) that leave little discretion, even thoughthey can be seen as constraints on free choice.19

Most pedestrian accidents occur when people have to crossvehicular traffic streams, as was pointed out before. The numberand intensity of incidents vary widely under different street con-ditions and among various population groups. For example, thereare many more accidents with cars turning left than with thoseturning right. This is due largely to the impaired field of vision ofthe driver and some confusion as to who should yield the right-of-way. Zebra stripes at crosswalks are highly recommended traffic

markings, but they do not necessarily reduce accidents becausemany pedestrians ignore them, and motorists have the right toexpect that walkers will stay within the designated space. A com-mon cause of serious accidents is children who run into the streetfrom between parked vehicles. Elderly people also experiencehigher accident rates, presumably due to being less agile in get-ting out of the way and moving more slowly than anticipated bysome impatient motorists.

The most dangerous, and most deplorable, situation is theabsence of sidewalks at all in many low-density suburban areas,

18 The author tends to brag about the two jaywalking tickets that he has received

on the streets of New York as proof of his personal independence, recognizingfull well that this represents a juvenile attitude.19A loud controversy was generated in New York in late 1997 when Mayor Giu-liani caused short fences to be erected at high-volume pedestrian intersections

near Rockefeller Center, limiting the crossing of avenues to the upstream side

only. This was seen as an effort to primarily expedite vehicular movement,although undoubtedly there is a strong pedestrian safety feature as well. They

are now grudgingly accepted.

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Walking 33

forcing the few walkers to use the street pavement or the narrowshoulder. Joggers on busy streets are particularly vulnerable.

The other dimension of concern is personal securitythe

potential for criminal or threatening behavior by other peoplewithin pedestrian environments. Again, walkers, especially whenthey are alone, are vulnerable in certain situations. The possiblecountermeasures, besides the visible presence of police, are goodlighting, clear visibility in all directions, absence of hiding placesand secluded enclaves, andabove allmany people on thewalkways at all times who maintain eyes on the street.

Application ScenariosA strong argument can be advanced that a basic walkway networkshould extend over theentire communitywhere people live, work,and use various facilities. All points should be accessible on foot,with some convenience and safety. The only exceptions might bevery local streets (cul-de-sacs and loops) where motor traffic isminimal and people have obvious prioritystreets that are for-mally or in effect traffic-calmed. The desirable system, then,would be a completely interlinked network of sidewalks and walk-ways, with adequate dimensions and surface quality and equipped

with proper safety arrangements at all crossings of significantvehicular movement.

There will be always places within any city where the existingor desirable pedestrian flows are sufficiently intense to applyimprovement programs beyond the standard provision of side-walks. These are opportunities to structure an urban environmentat an enhanced level of livability, convenience, and attractive-ness. Such obvious nodes are commercial and service districts,entertainment and sports centers, stadiums, major education andcultural institutions, transit stations, and similar venues where

people congregate. These patrons deserve the means to move toand from them on foot, which suggests the development of specialor improved walkways leading to and from the surrounding dis-tricts and principal access points (stations and parking lots). Inmany instances, interior circulation networks within special dis-tricts and campuses are likewise candidates for careful planningand construction of walkways.

Any pedestrian plan has to recognize certain external, ratherobvious, factors that significantly influence the demand for facil-

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Streets in cities serve many purposes besides carrying

vehicles, and city sidewalksthe pedestrian parts of the

streetsserve many purposes besides carrying pedestri-

ans. These uses are bound up with circulation but are

not identical with it and in their own right they are at

least as basic as circulation to the proper workings of

cities.

A city sidewalk by itself is nothing. It is an abstrac-

tion. It means something only in conjunction with the

buildings and other uses that border it, or border other

sidewalks very near it. The same might be said of streets,

in the sense that they serve other purposes besides carry-

ing wheeled traffic in their middles. Streets and theirsidewalks, the main public places of a city, are its most

vital organs. Think of a city and what comes to mind? Its

streets. If a citys streets look interesting, the city looks

interesting; if they look dull, the city looks dull.

More than that, and here we get down to the first

problem, if a citys streets are safe from barbarism and

fear, the city is thereby tolerably safe from barbarism

and fear. When people say that a city, or a part of it, is

dangerous or is a jungle what they mean primarily is

that they do not feel safe on the sidewalks. But side-

walks and those who use them are not passive benefi-

ciaries of safety or helpless victims of danger.

Sidewalks, their bordering uses, and their users, areactive participants in the drama of civilization versus

barbarism in cities. To keep the city safe is a fundamen-

tal task of a citys streets and its sidewalks.

This task is totally unlike any service that sidewalks

and streets in little towns or true suburbs are called

upon to do. Great cities are not like towns, only larger.

They are not like suburbs, only denser. They differ from

towns and suburbs in basic ways, and one of these is

that cities are, by definition, full of strangers. To any

one person, strangers are far more common in big cities

than acquaintances. More common not just in places of

public assembly, but more common at a mans own

doorstep. Even residents who live near each other are

strangers, and must be, because of the sheer number of

people in small geographical compass.

The bedrock attribute of a successful city district is

that a person must feel personally safe and secure on

the street among all these strangers. He must not feel

automatically menaced by them. A city district that fails

in this respect also does badly in other ways and lays up

for itself, and for its city at large, mountain on moun-

tain of trouble.

This is something everyone already knows: A well-

used city street is apt to be a safe street. A deserted city

street is apt to be unsafe. But how does this work,

really? And what makes a city street well used or

shunned? . . . What about streets that are busy part of

the time and then empty abruptly?

A city street equipped to handle strangers, and to

make a safety asset, in itself, out of the presence of

strangers, as the streets of successful city neighborhoods

always do, must have three main qualities:First, there must be a clear demarcation between

what is public space and what is private space. Public

and private spaces cannot ooze into each other as they

do typically in suburban settings or in projects.

Second, there must be eyes upon the street, eyes

belonging to those we might call the natural proprietors

of the street. The buildings on a street equipped to han-

dle strangers and to insure the safety of both residents

and strangers must be oriented to the street. They can-

not turn their backs or blank sides on it and leave it

blind.

And third, the sidewalk must have users on it fairly

continuously, both to add to the number of effectiveeyes on the street and to induce the people in buildings

along the street to watch the sidewalks in sufficient

numbers. Nobody enjoys sitting on a stoop or looking

out a window at an empty street. Almost nobody does

such a thing. Large numbers of people entertain them-

selves, off and on, by watching street activity.

In settlements that are smaller and simpler than big

cities, controls on acceptable public behavior, if not on

crime, seem to operate with greater or lesser success

through a web of reputation, gossip, approval, disap-

proval and sanctions, all of which are powerful if people

know each other and word travels. But a citys streets,

which must control the behavior not only of the people

of the city but also of visitors from suburbs and towns

who want to have a big time away from the gossip and

sanctions at home, have to operate by more direct,

straightforward methods. It is a wonder cities have

solved such an inherently difficult problem at all. And

yet in many streets they do it magnificently.

(From The Death and Life of American Citiesby Jane Jacobs (Random House, 1961, pp. 2930, 3435), copyright 1961 by

Jane Jacobs. Used by permission of Random House, Inc.)

The book The Death and Life of Great American Citiesby Jane Jacobs revolutionized thinking about

cities. The key theme was a return to the traditional street as the focus of urban life where the activepresence of local residents ensures safety and a sense of community.

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Walking 35

ities. People walk much more in high-density areas than in lightlydeveloped places, because there are more destination pointswithin walking range. Likewise, communities with a large popu-

lation of older residents and children will show more people onfoot than those with an average demographic composition. Males25 to 54 years old are the least active participants. Almost alltraffic to a corner grocery store (if it still exists) in a dense citywill be on foot; almost nobody can or will walk to a regional shop-ping center. Except for movement associated with commuting,most walking will occur in the middle hours of the day.

(The development of walkway systems with a purely recre-ational purpose within open spaces and along water bodies is amost desirable action as well, but it is not exactly transporta-

tion; therefore, it is not included in this discussion. Similarly,the creation of civic spaces is a subject for other analyses, rec-ognizing that they too generate major pedestrian presence andflows.)

Components of Walking SystemsThe presumably ubiquitous pedestrian system in any communityconsists of only a few rather simple physical elements, butgiventhe importance of this networka closer examination of each is

warranted.

Sidewalks and Walkways

Sidewalks are normally placed within the public right-of-way oneither or both sides of the central vehicular channel, within themarginal reserved strips, which will usually be at least 7 ft (2 m)wide (with a 50-ft [15-m] right-of-way and a 36-ft [11-m] pave-ment). The sidewalk itself should be at least 5 ft (1.5 m) wide,where the governing consideration is not the size of persons, butrather the ability of two baby carriages (or mail carts or wheel-

chairs) to pass each other. In higher-intensity areas, the sidewalksare frequently 8 ft (2.4 m) wide; in commercial districts of largecities, they may be 15 ft (4.6 m) wide or more.

Sidewalks may be placed directly adjacent to the curb, therebyallowing some savings in construction costs, but with the draw-back that pedestrians will be in very close proximity to movingvehicles, and the opening of doors from parked cars may createobstructions to pedestrians. A preferred approach is to place side-

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6 to12-ft sidewalk retail/caf zone

6 to 10-ft pedestrian

circulation area

3 to 4-ft street tree, pole,

and utility zone

Figure 2.1 Activity street with intensive sidewalk use (green street).

walks directly or almost adjacent to the outside right-of-way line,which creates a buffer strip between the sidewalk and the curb.This strip provides a safety zone that can be landscaped. It is

advisable to place utility lines under the unpaved strips, therebymaking repair and excavation less costly.The utility of sidewalks is frequently impaired by various

obstructionssign- and lampposts, hydrants, mailboxes, busshelters, newspaper vending machines, parking meters, trees, andbenches, not to mention protruding outdoor cafes, producestands, and staircases. All this may be useful and necessary, butthe effective sidewalk width will be thereby reduced (as is dis-cussed later under Capacity Considerations; also see Figs. 2.1to 2.3).

In most communities the responsibility for maintaining andcleaning the sidewalk rests with the adjoining property owner,even though it is located in a public right-of-way. The local land-lords have to ensure that broken surfaces are repaired to precludeaccidents, that snow and debris are cleared to allow passage, thatwater does not flood the paths, and that the facility is generally ofadequate quality. They may receive citations for negligence, and

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Walking 37

8 to 12-ft sidewalk

3 to 8-ft street tree, pole,utility and bus loading zone

10-ft curb lane bus and

parking zone

Traffic lane

Figure 2.2 Urban street with regular sidewalk.

Rest area with bench, litter bin,

and community billboard

6 to 8-ft sidewalk

3 to 4-ft street tree,

pole, and utility zone

Figure 2.3 Suburban street with pedestrian amenities.

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injured parties may sue the private owners as well as the munici-pality. The owners have the duty at least to notify the appropriatecity agency about problems and deficiencies.

Surfaces

The type of material used for sidewalks and the resulting surfacefinish have at least three areas of concern: ease of walking, per-manence, and visual attractiveness.

The most common type of construction is poured concretewith wire mesh reinforcement. It is easy to build, since not muchsubsurface preparation is necessary (no heavy loads will have tobe carried); the surface is nonslip and watertight, and the pave-

ment is durable. Some shortcomings are that the surface is notparticularly interesting, the repair effort is rather extensive whenthe slabs crack or break, and the surface is hard on the feet (inevery possible sense).

Bituminous blacktop pavement is usually cheaper yet, andconstruction is very easy. It has a great advantage in that thematerial is somewhat resilient, thus offering very good walkingquality. However, this softness (the surface may even melt undervery hot sun) makes blacktop unsuitable for real urban applica-tionsharp heels and small hard wheels will destroy the surface

rather quickly. While repairs are easy, the patched patterns andthe overall common appearance of blacktop walkways makethem suitable only for long recreational paths, where most userswill wear shoes with soft soles.

The most attractive surfaces in general use are provided byspecial paving blocks and brick. Various sizes and shapes areavailable, and interesting geometric designs can be achievedpleasing to the eye as well as to the feet. These materials are moreexpensive, and great care has to be taken in construction to main-tain the integrity and evenness of the surface. Individual elements

may become dislodged, and such surfaces become uncomfortableto walk on because the ankles are continuously twisted. A pro-trusion of even half an inch may trip some people.

At the top of the line are stone slabs and polished terrazzo.Undoubtedly, they give the best impression due to the rich qual-ity of the material, and they are quite durable. The problems arehigh cost and the slippery conditions that are quite likely to occurwith any moisture.

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Walking 39

Drainage and Lighting

Full and uninterrupted utilization of pedestrian facilities dependsto a significant extent on overcoming natural constraints, which

in this case are too much water and darkness. The need fordrainage systems is rather obvious and unavoidable, not only tomaintain clear paths at all times, but also to ensure that no struc-tural damage is done to the infrastructure through gradual ero-sion or sudden wash-outs.

Lighting is not a mandatory requirement, but is to be expectedanywhere that urban life continues beyond dusk. It is not only amatter of maintaining adequate and uniform illumination levelsalong the entire walking system, it is also an opportunity to cre-ate and heighten visual interest within the pedestrian environ-

ment. Crime prevention is a significant consideration, withwell-lit paths and spaces to deter criminal activity (or at least topush it to the dark places).

Traffic Control Devices and Accessibility Concerns

There should be no constraints on the movement of pedestrians,and people should be able to proceed with no unwanted stops,even if they have some handicaps to walking. This may hold forideal situations only; in real life, adjustments need to be made.First, there are the many crossings with vehicular traffic that willbe present in any pedestrian network. The needs and choices arequite well understood and worked out by this time, and variouslevels of controls are availableincluding simple stop signs forvehicles, regular traffic signals, and controls with special phasesfor pedestrians. However, in American communities remindersare needed that walking is a legitimate transportation mode thatshould be encouraged and that its participants need some protec-tion. Their presence should be recognized in the timing anddeployment of signals and traffic controls, which routinely tendto take into account the speed of cars, not of pedestrians.20

It is now the law of the land that people with physical or men-tal impairments should receive every consideration when systems

20 Manhattan avenues, for example, have signals timed to move cars in a greenwave over long distances. The experience of the author over many years shows

that a pedestrian moving at a normal pace, either with or against the traffic flow,

will face a red signal at every intersection.

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are designed and built so that they are not excluded from partici-pation (as much as is reasonably possible). This certainly appliesto walking, and includes the requirements that public walkways

must not encompass steep grades (no slopes along the path inexcess of 1:12),21 and that there must be no steps or curb facesalong the way. The latter requirement results in curb cuts at inter-sections in all the directions that people may travel. Curb cuts notonly allow wheelchairs to move without great difficulty, they alsoassist all others who find climbing up and down somewhat of achore. Another set of desirable improvements address the needs ofpeople who have impaired vision. These improvements includetactile surface treatments that can be sensed along edges and atpoints where care has to be exercised (at intersections, for exam-

ple), traffic signals accompanied by audible sounds indicatingWalk or Dont Walk conditions, and the clearance of obstructionsthat may be difficult to see or sense otherwise (Figs. 2.4 and 2.5).

Grade Separation and Multiple Levels

At places where vehicular traffic is heavy and serious conflictsmay occur, grade-separated paths are most desirable. There havebeen thousands of such idealistic or practical designs, but not toomany have actually been implemented. The concern is not one ofcost only; there is always the potential problem of whether people

will actually use them. If the vehicular flow is not an absolutelysolid wall and the protected passage consumes longer time oreffort, many walkers will take a risk and follow any shortcut.

Pedestrianoverpasses bridging heavy motorways are the easi-est type to implement because they can be relatively light struc-tures (carrying only people), even though they may have to bebuilt rather high to provide enough headroom for large trucksbelow. This fact also embodies the principal problem: users face ahigh climb upward, which they are most reluctant to undertake,even knowing that coming down on the other side will be easier.

Another problem is that in some places the younger members ofthe community find great sport in bombarding the cars below

21 This means that the centerline rises or falls vertically no more than 1 unitwithin a 12-unit distance horizontally. Grades (or gradients) are also expressed

as percentages, i.e., measuring the vertical change over 100 units horizontally.

The 1:12 ramp corresponds to an 8.3 percent grade.

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30/46


Building Line

Bus Stop

Bus Stop

RightTurnOnly

Subway Stairs or

NewsstandCha

mferedCorne

r

Ramp

Ramp

Ramp

Ramp

Bulb-Out

Bulb-Out

Refuge Island MedianMedian

Crosswalk

Parki

ng

Parking

Curb

Figure 2.5 Possible pedestrian crossing arrangements in a high-density district.

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Walking 43

from the overpass. An early famous example was the footbridgeacross Broadway at Fulton Street in Manhattan (in the 1860s),which was lightly used, became a nuisance, and was soon

removed.The actual results, as frequently seen in cities, are ratherunsightly caged tubes with formidable staircases on both sideseffective only if all possible at-grade shortcuts are fenced off.They will be built when they have to be built. Good architecturaldesign may be of some help, particularly because they usuallyhave a very prominent visual location. Overpass structures mayalso serve as gateways to districts and as the scaffolding for signs,information, and artwork. The real solution would be to provideescalators, at least up, but they are expensive, particularly

because they do not operate reliably if left exposed to the weather.There are some fortuitous instances in which an overpass withelevators and escalators can be built in conjunction with a transitfacility, even if it is only a major bus stop. A fully acceptable over-pass should be able to accommodate wheel-chairs, which means a ramp extending for aconsiderable distance or taking the form of ahelix is needed.

Underpasses (pedestrian tunnels under road-ways), on the other hand, offer more attractive

possibilities, even if they are more expensivethan light bridges. The vertical clearances areless (8 ft for pedestrians), and the walking entryis always downward (people do not always con-sciously think of the need to climb up a shorttime later). The more successful examples havegently sloping ramps with well-landscaped orotherwise attractive sides. They tend to be expen-sive to build, particularly if utility connectionshave to be maintained under the street above,

and care with drainage systems is always neededto keep them dry.

The principal problem with underpasses isreal or perceived threats to personal securityallof us have seen enough Hollywood movies thatshow what can happen when good people gettrapped in tight tubes. Therefore, they can onlywork if high levels of illumination are main-

System of second-level overpasses in Shanghai,

China.

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tained, the tunnel is short, andevery part is completely visible.This means that any user must

be able to see fully to the exitend before he or she enters theunderpass.

All the preceding concernsalso apply when multilevel pe-destrian environments are con-sidered. The issues of populatingsuch paths and spaces with suffi-cient volumes of users have beenmentioned previously.

Roofs and Shade

The issue of providing weatherprotection on an open pedestrian

network has been touched on already. Inextreme climates, it is almost a must if reason-able volumes of walkers are to be attracted,and in temperate zones there are obvious ad-vantages as well. There is no need for a con-tinuous canopy, but occasional shelters aremost welcome. Frequently, advantage can betaken of nearby buildings to provide awningsand other devices against rainfall, sleet, snow,wind, and extreme sun conditions. Wheneverthey are uncomfortable, people will seek pro-tection indoors.

Landscaping and Amenities

Pedestrians appreciate visually attractive en-

vironments; indeed, it cannot be expectedthat paths and spaces will be popular if sig-nificant attention is not devoted to such fea-tures. Also, walkers need resting places fromtime to time. Landscaping, coordinated graph-ics, and attractive street furniture are all apart of the design challenge. Since these tasksenter into the realm of architecture and urbanSecond-level walkways in central part of Hong Kong.

Pedestrian underground mezzanine in Vienna, Austria.

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34/46


To overcome the problem ofslowness, there have been sev-eral efforts to design a variable-

speed belti.e., a device thatmoves slowly at both ends butpicks up speed in the middleportion. While there are severalimaginative design ideas on howto do that, there are no opera-tional examples yet. (Such a de-vice may be introduced on theParis metro system, and explo-rations are under way again in

New York.) Side entry/exit on amoving sidewalk are intriguingpossibilities, but are not likelyto be attempted by any agency

concerned with personal injury lawsuits in the United States.The problem with all moving belts is that in these devices most

of the infrastructure has to be in motion, not just individual vehi-cles, and they have to be activated along their full length whetherthere are many users or only one at any given time, thus generat-ing considerable operational costs. Furthermore, a parallel walk-

way is still necessary, because some people will not or cannot usethese mechanical devices, which occasionally will be out of ser-vice for maintenance anyway.

Beyond closed environments, moving belts have been employedsuccessfully in comprehensive, separated (second-level) walkwaysystems in several worlds fairs and major exhibition sites. Theyoperate in the Tacoma business center, at the Hollywood Bowl,and in some European city cores in a largely open public environ-ment.

The other possible device for mechanical assistance in pedes-

trian areas is a low-speed train of small open cars pulled by atractor or locomotive. These are quite common in pedestrianmalls, amusement parks, and large parking lots. They are usu-ally open so that riders can enter and exit quickly, and theyoperate as a convenience service; i.e., they usually charge nofares. Frequently, to maintain a local design theme, they are dec-orated in appropriate style, or at least made colorful and in-

Network of moving belts at the Worlds Fair in Osaka, Japan.

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Walking 47

viting. The principal functionalcharacteristics of these trainsare that they are small enough

and slow enough that they canmix freely with pedestrian traf-fic, not being seen as a threat towalkers. Examples are found inpedestrian malls in Miami Beachand Pomona, in parking lots atDisneyland and Disney World,in the San Diego and Bronx zoos,along the boardwalk of AtlanticCity, and at a number of other

places with intensive pedestrianflows in North America.

Capacity ConsiderationsThe estimation of walkway capacities is not an easy task, becausepeople on public paths and in pedestrian spaces do not followfully predictable patterns of movement, and sometimes do notmove at all, as discussed earlier. To bring some rationality to this

situation, capacity analyses are separated into two distincttypes:23

Linear paths,where there is mostly purposeful motion, almostentirely in two directions (such as sidewalks and corridors)

Area situations, where movement may be in any direction,and participants may simply occupy space for varying peri-ods of time within the confines of a designated floor area(such as station mezzanines and platforms, outdoor roomsused for any purpose, and public squares)

Tractor-train on the boardwalk to assist pedestrians in Wildwood, New

Jersey.

23 These study methods, following the aforementioned work of Fruin and Benz, are

outlined in full detail in several articles and reference books. The basic referencefor all capacity investigations is theHighway Capacity Manual 2000 (Transporta-

tion Research Board, Washington DC, 2000), with pedestrian issues covered in

Chaps. 11 and 18. Shorter discussions are found in the Institute of Transporta-tion Engineers Transportation Planning Handbook, op. cit., pp. 227230 and 440

ff. and Traffic Engineering Handbook, op. cit., various sections.

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While human beings come in different sizes and shapes, for thepurposes of transportation analyses, it is assumed that all of themfit into an ellipse with 18- 24-in (45- 60-cm) dimensions as

the basic design unit. This represents a base density of 3 ft

2

perperson (0.28 m2 per person or 3.6 persons per m2), but notcrush conditions, which are a matter of cultural tolerance ordire necessity. On some overloaded trains in developing coun-tries, 0.9 ft2 per person (12 persons per m2) have been observed,which would cause broken ribs, except that some of them arehanging on to the outside and some are sitting on the roof. In theindustrialized countries, crowding at the 2-ft2 (0.2-m2)-per-person level may be acceptable only on trips with very short dura-tion (in elevators, for example; floor space needs in vehicles are

discussed further in various chapters under Capacity).On the other hand, people feel comfortable only if they areable to preserve their own private space bubble, which tends tobe 8 or 10 ft2 (0.8 m2) in areathe approximate size of an openumbrella.24

All the preceding refers to people when they are standing.Since this is a discussion ofwalking, the moving state is moreimportant, and it is more complex. Basically, the space needs arelarger because a walker has to step forward into an area thatshould be open. The fundamental relationships in determining

pedestrian flow capacity arespeedvolumedensity.An overridingconsideration in these analyses is the concept oflevel of service(LOS). This is a qualitative measure that characterizes various sit-uations with reference to the ease with which the operations canbe performed. For example, LOS A means that motion by anyindividual is not constrained by anybody else, while LOS Fdescribes an unacceptable situation in which extensive contactwith others will be necessary to make any progress. Each level isassociated with a specified space requirement (see Figs. 2.6 and2.7). For example, if only 12 ft2 per walker are available (LOS E),

continuous conflicts will be experienced, and speed will beretarded, but considerable capacity will be achieved. At about 8ft2 per person (0.7 m2) friction becomes excessive, and all move-ment will stop at 2.5 ft2 (0.2 m2).


24 Tolerated or welcome intrusions in each personal space will not be discussed

here.

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Walking 49

Figure 2.6 Illustrations of pedestrian walkway levels of service. [From Transporta-

tion Research Board, Highway Capacity Manual 2000 (National Research Council,

2000), p. 11-9. Copyright 2000 by the Transportation Research Board, National

Research Council, Washington, D.C.]

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500

400

300

200

100

10 20 30 40 50

Normal High Range

Maximum Values

Flow (persons per minute per foot)

Speed

(feetperminute)

Figure 2.7 Speedflow relationship. [From

data in Transportation Research Board,

Highway Capacity Manual 2000 (National

Research Council, 2000), p. 11-3.]

The highest observed rates of pedestrian flow on busy side-

walks are about 25 persons per minute per foot of sidewalkwidth. This occurs with a speed of 150 ft/min (2.5 ft/s; 0.76m/s, with a density of 5 to 9 ft2 [0.5 to 0.8 m2] per person) andit represents conditions close to LOS E (see Table 2.1). In specialinstances, such as in controlled pedestrian corridors and tunnels,35 persons per minute per foot can be reached and even exceededfor short periods. Actual pedestrian counts in the centers of thelarger cities in North America (Chicago, New York) have recordedaverages of 250 to 350 people moving past a point on a regularcity sidewalk within a minute. Volumes during the peak 15 min-utes have approached 500 per minute.

The preceding paragraph introduces another element thatrequires some explanationtheeffective width available for walk-ing, or theeffective space available for circulation. This recognizesthe obvious fact that people will not walk with their shoulders rub-bing against lateral obstructions, such as buildings, trees, parking

Table 2.1 Pedestrian Flow Characteristics on Walkways

Level of service*

Characteristic A B C D E F

Flow rate, pedestrians per min per ft Less than 5 57 710 1015 1523 VariableSpacing, ft2 per pedestrian More than 60 4060 2440 1524 815 Less than 8Walking speed, ft/min More than 255 250255 240250 225240 150225 Less than 150

* Pedestrian specialists have not yet agreed on the exact space standards. Several sets exist; the norms shown here are the ones

most frequently used. Research and discussions continue, and a commonly accepted set is promised soon.

Source: Transportation Research Board, Highway Capacity Manual 2000(National Research Council, 2000), p. 18-4.

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Walking 51

meters, and other vertical elements. Consequently, the physicalwidth may have to be reduced by 6 to 18 in (0.2 to 0.5 m) on eachside, depending on the severity of the marginal obstructions, if

any.

Linear Capacity

The simplest cases are situations in which pedestrians are in con-tinuous motion along a defined channel. If the movement is intwo directions, there will be some internal turbulence and frictionas people deviate from a straight line, but by and large they willwalk on the right-hand side and avoid contacts rather adroitly.Given sufficient time, they will establish reasonably uniform den-sities within the total mass. Nevertheless, individuals may meet

Linear Pedestrian Capacity ExampleCity Sidewalk

Effective width = 8 ft 2.5 ft (side obstructions) = 5.5 ft

Selected level of service = C/D (the break-point between LOS C and LOS D)

Flow rate = 10 pedestrians per minute per foot of width

Capacity = 10 5.5 = 55 walkers per minute or 3300 per hour

Or:

If there are 1400 walkers per hour westward and 1600 eastward, they will oper-ate at level of service C.

Walkers per minute = = 50

Walkers per foot of width = = 9.1

which corresponds to LOS C (see Table 2.1)

50

5.5

1400 + 1600

60

Pedestrian Flow AvailableWidth

Curb

Building Line

Mail boxParking Meters

Pedestrian Flow8 ft12 ft

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and stop for a chat in the middleof the stream,25 and other eventsmay occur that reduce the base

capacity performance.In a city, pedestrian flows,regrettably, do not follow straightlines for very long distances.There are crossings and inter-sections that interrupt smoothprogress. As a matter of fact, thegoverning capacity conditions arefound at street corners where peo-ple accumulate, awaiting the next

opportunity to proceed. In busyplaces, the complexities intensify,because other pedestrians walkingin a perpendicular direction have

to penetrate the crowd already assembled at the edgeof the sidewalk; other business or personal actions may take placeat the corners; and turning cars may impede the flow of peopleacross the street even if they have a Walk signal in their favor.If the volumes are large, two clusters of walkers will clash in themiddle of the street, and numerous evasive maneuvers will take

place.26

The consequences of all this are that pedestrian flows fre-quently become organized in platoons that act as a single body,that crosswalks will require special analyses because many userswill stray from designated paths, and that street corners meritspecial attention in terms of analyses (see next subsection, AreaCapacity). Frequently, in high-volume cases, street corners mayhave to be redesigned to gain sufficient pedestrian space bycleaning out all clutter, possibly chamfering building cornersand bulbing out the curb line. (The latter can only be done at

the expense of vehicular movement or parking lanes, but it alsohas the benefit of shortening the crossing distance from curb tocurb.

25 This is called aHolly Whyte encountershowing a complete disregard for themovement space of others, a phenomenon documented by W. H. Whyte.26 These complex situations require the attention of specialists and are not dis-

cussed in detail here.

chapter 2 - walking

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