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APPENDIX H: Team Conflict Survey Results This Appendix contains the results of the team-internal conflict survey to test the validity of the O&M Intervention measure used in NCHRP 3-78a. 125
NCHRP 3-78a Conflict Survey Results Providence Road at NC51, Charlotte, NC - PRE Condition February 2009 Instructions These were the instructions given to the team members: Dear NCHRP 3-78a Team Member, Please use the spreadsheet on the next tab labeled 'Conflict Log' to record your ratings of the clips on the conflict DVD mailed to you. The DVD contains 86 short video clips (~30 seconds each) of the PRE study at the intersection of Providence Road and NC51 in Charlotte, NC. These clips include all experimenter interventions, other events that we would consider risky, as well as, events that we consider safe. The clips are in random order, so you won't know which one is which. In rating the clips, please focus your assessment on the FIRST CROSSING DECISION shown in the video. Some clips may contain "rejected gaps" prior to crossing which should be ignored for this exercise. Note also, that not all "first crossing decisions" result in an actual crossing, since the Orientation & Mobility Specialist may have intervened. For example, an intervention may result in a forced yield which is then utilized for a crossing. Your rating should focus on the FIRST CROSSING DECISION, which in this case is the O&M intervention, not the crossing after the forced yield. On the rating sheet, please rate each clip using the following 1-5 rating scale: 1: Perfectly Safe - I believe that the initial crossing decision by the pedestrian was perfectly safe and that no emminent risk from approaching cars was visible 2: - I believe that the initial crossing decision by the pedestrian was somewhere inbetween ratings 1 and 3 3: Marginal Risk - I believe that the initial crossing decision by the pedestrian was tolerable and that the risk for a crash with an approaching vehicle was low 4: - I believe that the initial crossing decision by the pedestrian was somewhere inbetween ratings 3 and 5 5: Clearly Risky - I believe that the initial crossing decision by the pedestrian was clearly risky and that a crash with an approaching vehicle was very likely The DVD can be played on any DVD player or computer with DVD drive. If using a home DVD player, you can "skip" chapters as you would when watching a movie to access different clips. If using a computer, Windows Media Player allows you to select chapters directly. NOTE: Other DVD playback programs such as Power DVD may not recognize the chapters and will only allow you to play the first clip. The goal of this exercise is to expand our analysis of crossing safety beyond the O&M-Interventions measure. If you have any questions, please contact Bastian Schroeder at Bastian_Schroeder@ncsu.edu or 919-515-8565 Thank you for your assistance! 126
Observations - Twelve team members completed the conflict survey of the 86 clips, resulting in 1032 ratings. - The 86 clips consisted of a total of 35 O&M interventions, 27 other 'risky' events, and 24 'safe' events that were included to benchmark the test. The intervention category was based on field- coded intervention events by team member Wall Emerson. The 'risky' clips were selected by ITRE staff based on video observations. The 'safe' clips were included to benchmark this experiment and were selected because of the perceived low risk (based on ITRE assumptions). - Figure 1 shows the distribution of ratings for all intervention clips in three categories: SAFE (rating 1 or 2), MIDDLE (rating 3), and RISKY (rating 4 or 5). 0 2 4 6 8 10 12 2 5 6 8 9 11 12 15 16 20 21 22 25 27 30 32 34 35 36 38 39 41 42 44 45 50 53 56 58 63 73 79 81 83 86 Interventions SAFE (1 or 2) MIDDLE (3) RISKY (4 or 5) - The intervention clips (Figure 1) generally received high (risky) rating. However, almost all intervention clips (27 of 35) received at least one 'safe' rating on the "1-2" category. The two Figure 1: Distribution of Ratings for Intervention Clips 127
possible reasons are: 1) The intervention was difficult to see and was missed. 2) The observer disagreed with the need for the intervention. - The figure makes evident that most interventions tended to get risky ratings, but with some exceptions. The arguably riskiest clips were clips 8, 12, 34, 35, 39, 50, 53, and 56, all of which got no 'safe' ratings. Clip 34 was the only clip with consistent 4-5 ratings by all observers. - The average rating for intervention clips was 3.66, with 31 of 35 clips above a 3.0 average and 10 intervention clips with average rating above 4.0. The highest average rating was for clip 34 with a 4.92 average rating. 0 2 4 6 8 10 12 13 17 18 23 24 26 29 31 40 46 48 49 51 52 57 59 62 65 67 68 69 71 72 75 76 84 85 Risky Events SAFE (1 or 2) MIDDLE (3) RISKY (4 or 5) - The risky clips (Figure 2) were included based on reviewing video at ITRE. This category of clips showed the greatest amount of variability among observers. Figure 2 shows the resulting distributions for the 27 clips in this category. The results make evident that all clips tended to get some 4-5 ratings, but many also received 1-2 ratings, indicating that the observer did not perceive a great amount of risk in the crossing. - The average rating for risky clips was 2.99, with 12 of 27 clips above a 3.0 average and 2 clips with average rating above 4.0. One of the 'risky' clips received an average rating less than 2 (clip 23) Figure 2: Distribution of Ratings for Risky Clips 128
0 2 4 6 8 10 12 1 3 4 7 10 14 19 28 33 37 43 47 54 55 60 61 64 66 70 74 77 78 80 82 Safe Events SAFE (1 or 2) MIDDLE (3) RISKY (4 or 5) - The safe clips (Figure 3) were included to benchmark the test results. Overall, pedestrians crossed the CTL facility about 800 times in the 'pre' condition. The 'safe' clips were included on the conflict DVD as a representative sample of the approximately 750 crossing events that were not capture by the 'intervention' or 'risky' categories. The underlying hypothesis is that these clips would generally get 'safe' ratings, thereby validating the selection process (for 'risky' clips) conducted by ITRE staff. Figure 3 shows the resulting distributions for the 24 clips in this category. - The average rating for 'safe' clips was 1.69, with none of the 24 clips above a 3.0 average. The majority received an average rating less than 2.0 (19 of 24) and the highest average rating in this category was a 2.79. The results suggest that while these clips received occasional high ratings (4=5), observers predominantly agreed that no eminent risk was present in these crossings. - In a general observation, some clips were poorly chosen because multiple events were shown in the short video segment. In all five of these clips, an O&M intervention was followed by other pedestrian-vehicle interaction events. In some cases, the pedestrian actually crossed after the Figure 3: Distribution of Ratings for Safe Clips 129
intervention, creating ambiguity among observers about which event they should rate. These clips were numbers 22, 32, 44, 62, and 63. - Looking at the 'safe', 'middle', and 'risky' categories (i.e. a three-category simplification of the 1-5 scale) many clips had significant disagreement among observers. Of the 86 clips, only six had unanimous agreement among all observers (Clips 10, 33, 34, 66, 70, and 82). Another nine had one disagreement (Clips 4, 14, 19, 28, 35, 37, 55, 56, and 59), and eight addition clips had two disagreements from the mode (Clips 7, 9, 12, 22, 39, 43, 64 and 80). The remaining 59 clips had more disagreement. - Continuing to look at the variability amongst observers, people tend to differ in their perception of risk. Of the 86 rated clips, only 6 had a standard deviation of less than 0.5 on the 1-5 scale. The majority of the clip ratings had a standard deviation between 0.5 and 1.0 (50), with the remaining 30 clips having a standard deviation greater than 1.0. 130
