traffic analysis - trip generation
TRANSCRIPT
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Lec 26: Ch3.(T&LD): Traffic AnalysisTrip generation
Know the definition of site-oriented and non-site traffic
Understand the phases of site impact trafficevaluation (S.I.T.E.)
Learn how to estimate trips generated by adevelopment
Know how to use ITE Trip GenerationHandbook
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Site-oriented traffic vs. Non-site traffic
Without thedevelopment
With thedevelopment(new orexisting)
Site-orientedtraffic (tripshaving an ODon the site
Non-site traffic (noOD on the site)
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SITE Methodology
Phase I:Establish existing traffic conditionswithout the site (proposed)
Phase II:Forecast future traffic conditionswithout the site
Phase III:Forecast future site-only trafficconditions
Phase IV:Determine total future trafficconditions (II + III)
Phase V:Evaluate alternative improvements
Phase VI:Negotiations
Phase VII:Implementation
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Flow chart of SITE process
Existing BackgroundTraffic
CalculateLOS
Phase I
Phase IITraffic growthfactors
Input fromMPO andlocal/stateagencies
Future backgroundtraffic w/o site
Forecast trafficfor other newadjacent sites
Combine
CalculateLOS Compare
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Flow chart of SITE process (cont)
Forecast traffic for sitedevelopment
Phase III
Phase IVCombine
Total traffic
CalculateLOS
Compare
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Flow chart of SITE process (cont)
Develop alternativesolutions
Phase V
Phase VI
Begin negotiations betweenlocal officials and developers
Documentfindings
Evaluatesolutions
Feedback
Perform supplementaltechnical analyses
Feedback
Phase VII
Assist in preparingconstruction plans
Implementation
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Site-oriented traffic (site-generated trips): mucheasier to estimate because
The land use activities are known
The number of trips expected to be generated by theproposed development can be determined using the ITE TripGeneration Handbook
The present and future directional distribution can be
estimated
The total number of trips generated
The number of trips to and from the site during thepeak hours of the adjacent street
The number of trips to and from the site during thepeak(s) of the generator
Daily variation
Monthly variation
5 Primarycharacteristics
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Unit used as the base variable for trip-generation rates
Be functionally related to the volume of traffic generated(e.g. 48 trip ends per 1000 sq.ft floor area, 5.7 trip ends peroccupied dwelling unit)
Be relatively easy to establish/measure (meaning easy tomeasure the size, like size of an household, size of a store)
Provide consistent and transferable rates (Althoughvariations exist, establishments of similar characteristics havesimilar trip generation rates.
(See the handout)
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Issues (pp. 29, 39, 40)
Age of data baseNot much difference between old and new data
Daily variationsPeaking of traffic varies depending on the type ofdevelopment
Location variationITE trip generation data came from suburban areas(for vehicular trips)
Pass-by trafficSome generators attract traffic from the passing trafficstream
Mixed-use developmentMixed-use land may produce less trips thanthe sum total of individual land uses (many rates are derived from stand-
alone developments)Vehicular tripsThe generation rates are vehicular trips for average
vehicle occupancy
Variability in ratesvariation in data
Sample sizeSome have only a small number of samples
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Pass-by Traffic
Land use activities such as offices, industrial parks,
hotels, high-quality restaurants, and residentialdevelopment generate traffic which intends to have a tripend at the particular site and therefore constitute newtraffic on the street system.
However, a sizable portion of the traffic generated byfast-food restaurants and gas stations is already on theadjacent street and merely stops at the establishment inpassing by I.e. pass-by traffic. They are NOT newtraffic. They were there but because a new establishmentwas developed, they just decided to make a detour.
See Table 3-4 for variation of theamount of pass-by traffic bygenerator type and size, and Table 3-5 for daily variation, and Table 3-6 for
weekly variation
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Mixed-use development
When an activity center is developed with a mix of different landuses (e.g., retail and office), there are fewer trips on and off thesite than if the retail and office activities are developed onseparate sites. In a mixed-use development, some individuals willcomplete two or more purposes without leaving the site.
(See Table 3-7 and 3-8)
Shopping center
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Satellite development
Regional shopping centers attract other commercial retaildevelopments to property surrounding the center. Theinteraction (shared trips) may be 10% or more of the trafficgenerated by a satellite development. The number ofshared trips will be subtracted when it is loaded to the
external roadway. Note: this is not a chained-trip. Achained trip is a trip that combines different trip purposes(work, shop, day-care drop off, etc.).