factors influencing the perception of safety at intersectionsmicrosoft word - factors influencing...

1

Factors Influencing the Perception of Safety at Intersections Brittany Kubinski

Introduction In 2012, a series of accidents occurred during the first weeks of the semester at The Ohio State University prompting the University to form a Traffic Safety Task Force and to address the significant traffic safety issues on campus. While the task force was initially charged to provide an assessment of safety on campus as it relates to pedestrian and vehicular behavior and provide solutions, pedestrian and bicyclist safety on campus can always be improved and it is this situation that has prompted a study into perceived safety at intersections. Within Columbus, there is no area of greater need for enhanced pedestrian and bicyclist safety measures than Ohio State’s campus. With a student population of over 57,000 students and growing, pedestrians are constantly interacting with vehicles. Many intersection designs and characteristics exist in order to enhance pedestrian safety. Pavement markings of various designs, yield to pedestrians and pedestrian crossing signs, traffic islands and pedestrian crossing refuges all exist to aid in safe intersection crossing. The aim of this study is to understand which factors are most important in an intersections perceived safety. In order to analyze pedestrian perceptions of safety, a visual preference survey has been conducted that allows users to rank an intersection over another one based on how safe they perceive it to be. StreetSeen, a free tool that anyone can use to create, collect and analyze data was used to conduct a pairwise visual survey. Using geo-‐tagged images from Google Street View, the perception of intersection safety at The Ohio State University in Columbus, Ohio, is measured as perceived by people across the world. The results of this survey are then categorized into the least preferred and most preferred intersections. The attributes that those intersections are largely comprised of are then tallied to determine which attributes pedestrians find most important in the perceived safety of an intersection. Data and Methodology This section discusses the data set used for this study, its collection, and limitations. Following the section on data, the analysis methods are discussed. First we describe how we score each image using win/loss ratios (calculated based on the number of times an image is shown and the number of times it is selected over its paired image). Based on this analysis, we present and describe the most and least favored images. Data The survey conducted in this research was designed to obtain information on individuals’ perception of safety for intersections at The Ohio State University and the corresponding attributes of more preferred and less preferred intersections. For the visual preference survey, the survey creator selects one or more geographic areas and then selects the number of random images to be generated from Google Street View.

2

The images were sourced from Google Street View on The Ohio State University campus in Columbus, Ohio, USA. 50 images were selected to be included in the study to provide for a wide of intersection designs and types. Images were then categorized based on specific segment-‐level attributes, in a spreadsheet. The images and dataset used in the study can be downloaded from http://streetseen.osu.edu/studies/which-‐intersection-‐would-‐you-‐feel-‐the-‐safest-‐crossing/vote. Perception data was collected using StreetSeen, as shown in Figure 1 of the Appendix. Users were shown two images, selected randomly from the dataset, and asked to select one in response to the question “Which intersection would you feel the safest crossing?” The survey also collected data on their location, based on the latitude and longitude when completing the survey as well as answers to survey questions about gender, age and commuting behaviors such as: Thinking about a typical day how many streets would you estimate that you cross? How do you typically get to school or work? As well as questions to determine if they are currently enrolled at a university. The locations of images are illustrated in Figures 2, 3 and 4 in the Appendix. The images were selected to provide a variety of segment-‐level attributes that affect cycling preferences. These attributes and the range of levels considered for each attribute are listed below.

• Crosswalk o Painted with ladder markings o Painted with parallel markings o None

• Segment Intersections o No intersections o 3 way intersection o 4 way intersection

• Condition of Road o Good (very few bumps/cracks/holes) o Fair (some bumps/cracks/holes) o Poor (many bumps/cracks/holes) o Under Repair (clear work is underway)

• Number of Lanes o 1 lane o 2 lanes o 3 lanes o 4+ lanes with raised median o 4+ lanes without raised median

• Traffic Control Devices o Stop Sign o Traffic Light o None

3

• Crossing Aids in Segment o Pavement Markings o Yield to Pedestrian Sign o Pedestrian Signal o Median/Traffic Island/Pedestrian Refuge o Curb Extension o Overpass/Underpass o Pedestrian Crossing Sign o Flashing Warning o Share the Road Warning

• Cars Visible o None o Low (2 or fewer cars) o Medium (3-‐5 cars) o High (6-‐9 cars) o Very High (10+ cars)

• Pedestrians Present • Bicycles Present • Distance Crossed

o Not more than 50' o More than 50'

• Stopline Setback o Setback present behind crosswalk o No setback

• Curb Cuts/Ramps o Curb cuts/ramp present o No curb cut/ramp

• Condition of Crosswalk o Markings are well maintained o Markings are faded o No markings

• Speed Limit o >= 35 mph o < 35 mph o Not Posted

Survey Administration More than 9,000 students enrolled and active in TechniCity, a massive open online course, were invited to participate in the StreetSeen survey. The survey was also distributed on various social media websites such as Facebook, Twitter and LinkedIn.

4

A total of 203 people responded to the survey (as determined by unique IP addresses) and contributed 2.710 votes for preference of one image over another. Each participant contributed an average of 13 votes. Voters from all over the world contributed responses to this survey. As seen in Table 1 of Appendix 2, a total of 35 countries were represented with 90 voters from the United States making up the largest portion of voters at over 44 percent and contributing over 46 percent of the total votes. Voters from Spain (12), Canada (10) and Brazil (9) are responsible for six percent, five percent and four percent of the total votes, respectively. Results This study has yielded interesting results as to what factors most influence perception of safety at an intersection. Tables 2 and 3 in Appendix 2 lists the attributes that were present in the most preferred and least preferred intersections. First, having a crosswalk for pedestrians is essential in enhancing their safety as well as making them feel safe. For the most preferred intersections (those preferred over 50 percent of the time) we found that intersections with a ladder-‐patterned crosswalk were most preferred, with 58 percent of those intersections having a ladder style crosswalk. Figures 5, 6, and 7 in Appendix 1 were the most preferred intersections, each having been chosen 91 percent, 80 percent and 79 percent of the time, respectively. The next factor that leads individuals to feel a particular intersection is safe or unsafe is the condition of the road and the condition of the crosswalk markings. Within the top 50 percent of the intersections, 88 percent of the roads were in good condition (very few bumps, cracks and holes) and 81 percent of the intersections had well-‐maintained crosswalk markings. This factor is one that is easy enough to control for and just implies that the University should pay close attention to the conditions of the roads closest to intersections and pedestrian crossing areas and that crosswalk markings should be well-‐maintained in order to make pedestrians feel safe when crossing an intersection. Pavement markings were largely the most popular pedestrian crossing aid in use at these intersections but the yield to pedestrian and pedestrian crossing signs along with pedestrian signals were also prevalent. Intersections with fewer lanes/distances to cross were also among the most preferred locations. Figures 5, 6, 7 illustrate how 2 lane roads and short crossing distances were one of the factors that lead to these locations being highly preferred, while Figures 8, 9, and 10 demonstrate how the least preferred locations (chosen only 7 percent, 11 percent and 16 percent of the time, respectively) all have large crossing distances in common as well as 4 or more lanes of traffic to cross without any pedestrian refuge or traffic island to break up the distance. Volume of traffic was another factor that influenced perception of safety. Images with higher numbers of cars visible within the image were chosen less of the time than those with no cars or lower numbers of cars visible within the image. The top 3 least preferred intersections all

5

have higher levels of traffic and the cars appear to be moving at a faster speed than those of the top 3 most preferred intersections. Recommendations The purpose of this study was to identify which intersection attributes enhance a pedestrians perception of safety. By conducting this survey, it is the hope of the author to provide recommendations that The Ohio State University can use to prioritize funding for intersection installations or upgrades. In addition, by identifying specific intersections on campus that appear to be less safe, the University can target its efforts to improve these intersections. One of the most important factors in enhancing perception of safety is to reduce the distance to cross a street as well as the number of lanes and speed of traffic. Considering the nature of the university and its current walkability, one recommendation would be to reduce the number of lanes for campus streets. However, on streets where this cannot be achieved, lowering the speed limit and adding traffic islands and pedestrian refuges may also help to enhance perceptions of safety. Additional pedestrian crossing aids also help to give the intersection an enhanced feeling of safety. The most favored intersections often had two or more crossing aids in place (pedestrian crossing and yield to pedestrian signs, pedestrian signals and crosswalk markings). Additional crossing aids could also be added to existing intersections such as pedestrian overpasses and underpasses, flashing warnings and curb extensions. It is apparent from this visual preference survey that crosswalk markings that are more prominent lead to an enhanced perception of safety. While ladder-‐style crosswalks are one type of crosswalk design, other designs and materials could be utilized to create a more distinct pathway for crossing pedestrians. From this study, we have been able to determine that, indeed, well-‐maintained roads and intersections with additional pedestrian crossing aids, as well as shorter distances and less lanes all help to increase pedestrian comfort. The University should seek to take these factors into consideration when making infrastructure improvements on campus to existing intersections as well as when adding additional crosswalks on campus.

6

Appendix 1: Figures

Figure 1: Screenshot of the visual preference survey using Street Seen

Source: streetseen.osu.edu

Figure 2: Map of locations of images selected on OSU Campus


7

Figure 3: Map of locations of images selected on Woody Hayes Drive/Woodruff Avenue


Figure 4: Map of locations of images selected on Neil Avenue


8

Figure 5: Image of most preferred intersection, chosen 91% of the time.

Source: http://www.streetseen.osu.edu/locations/52730

Figure 6: Image of second most preferred intersection, chosen 80% of the time.


Figure 7: Image of third most preferred intersection, chosen 79% of the time.


9

Figure 8: Image of least preferred intersection, chosen 7% of the time.


Figure 9: Image of second least preferred intersection, chosen 11% of the time.


Figure 10: Image of third least preferred intersection, chosen 16% of the time.


10

Appendix 2: Tables

Table 1: Number of Voters by Country Country Number of Voters Australia 4 Austria 1 Blank 10 Brazil 9 Canada 10 China 1 Croatia 1 France 3 Germany 3 Greece 6 India 8 Iraq 1 Ireland 2 Israel 1 Italy 2 Japan 2 Kazakhstan 1 Mexico 5 Netherlands 4 New Zealand 2 Pakistan 1 Peru 1 Poland 3 Portugal 3 Puerto Rico 1 Russia 2 Rwanda 1 Senegal 1 Singapore 2 Spain 12 Taiwan 1 Turkey 1 United Arab Emirates 3 United Kingdom 4 United States 90 Venezuela 1 Total 203

11

Table 2: Number of Votes by Country Country Number of Votes Australia 60 Austria 15 Blank 109 Brazil 110 Canada 141 China 15 Croatia 15 France 45 Germany 32 Greece 77 India 66 Iraq 15 Ireland 25 Israel 15 Italy 30 Japan 21 Kazakhstan 16 Mexico 61 Netherlands 60 New Zealand 9 Pakistan 15 Peru 15 Poland 35 Portugal 45 Puerto Rico 15 Russia 30 Rwanda 15 Senegal 15 Singapore 31 Spain 158 Taiwan 15 Turkey 15 United Arab Emirates 31 United Kingdom 60 United States 1263 Venezuela 15 Total 2710

12

Table 2: Most Preferred Intersection Attributes Favored More than 50% of the Time

Number of Locations 26 100% Crosswalk

Painted with ladder markings 15 58% Segment Intersections

3 way intersection 11 42% Condition of Road

Good (very few bumps/cracks/holes) 23 88% Number of Lanes

2 lanes 22 85% Traffic Control Devices

Traffic Light 9 35% None 9 35%

Crossing Aids in Segment Pavement Markings 24 92%

Yield to Pedestrian Sign 2 8% Pedestrian Signal 9 35% Curb Extension 1 4%

Pedestrian Crossing Sign 7 27% Cars Visible

None 9 35% Pedestrians Present 17 65% Bicycles Present 3 12% Distance Crossed

Not more than 50' 25 96% Stopline Setback

Setback present behind crosswalk 16 62% Curb Cuts/Ramps

Curb cuts/ramp present 24 92% Condition of Crosswalk

Markings are well maintained 21 81% Speed Limit

Not Posted 26 100%

13

Table 4: Least Preferred Intersection Attributes Favored Less than 50% of the Time

Number of Locations 24 100% Crosswalk

Painted with parallel markings 13 54% Segment Intersections

4 way intersection 11 46% Condition of Road

Good (very few bumps/cracks/holes) 13 54% Number of Lanes

2 lanes 11 46% 4+ lanes without raised median 8 33%

Traffic Control Devices Traffic Light 10 42%

None 8 33% Crossing Aids in Segment

Pavement Markings 14 58% Yield to Pedestrian Sign 2 8%

Pedestrian Signal 10 42% Pedestrian Crossing Sign 1 4%

Cars Visible Medium (3-‐5 cars) 9 38%

Pedestrians Present 9 38% Bicycles Present 3 13% Distance Crossed

Not more than 50' 14 58% More than 50' 8 33%

Stopline Setback Setback present behind crosswalk 11 46%

No setback 11 46% Curb Cuts/Ramps

Curb cuts/ramp present 18 75% Condition of Crosswalk

Markings are faded 7 29% No markings 8 33% Speed Limit

< 35 mph 1 4% Not Posted 21 88%

factors influencing the perception of safety at intersectionsmicrosoft word - factors influencing...

Documents