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59 CHAPTER 5. RECOMMENDED HSM METHODOLOGY This chapter summarizes the recommended pedestrian safety prediction methodology for application in HSM Chapter 12 (formerly designated as HSM Chapter 10). SIGNALIZED INTERSECTIONS A revised methodology for predicting pedestrian safety at signalized intersections has been developed to replace the current methodology (25) that is based on Equation (3) and Table 7. The recommended methodology includes base models for 3SG and 4SG intersections shown in Equations (20) and (21), respectively. The recommended methodology also includes AMFs for bus stops, schools, and alcohol sales establishments presented in Chapter 4 of this report. While these AMFs were developed for 4SG intersections, it appears reasonable to assume that these same AMFs can be applied to 3SG intersections, as well. In other words, it is presumed that similar pedestrian behavior would be observed at both 3SG and 4SG intersections, but that statistically significant relationships for 3SG intersections were not found because of the low vehicle-pedestrian frequencies at 3SG intersections. It is anticipated that not all HSM users will have pedestrian volume counts available for signalized intersection to which the HSM methodology will be applied. Table 23 provides guidance on the estimation of specific pedestrian volumes for signalized intersections with general pedestrian activity levels. The pedestrian volumes estimates in the table represent the sum of all daily pedestrian crossing volumes at an intersection and are based on percentiles of the combined pedestrian crossing volume data for the Toronto and Charlotte intersections, as follows: General pedestrian activity level Pedestrian volume percentile in combined Toronto and Charlotte data High 90th percentile Medium-high 75th percentile Medium 50th percentile Low-medium 25th percentile Low 10th percentile The pedestrian volume estimates in Table 23 may be calibrated by individual highway agencies to match their local conditions.
60 Table 23. Guidelines for Estimating Pedestrian Crossing Volumes Based on General Pedestrian Activity Levels Estimated pedestrian crossing volume (pedestrians/day) General pedestrian activity level 3SG intersections 4SG intersections High 1,700 3,200 Medium-high 750 1,500 Medium 400 700 Low-medium 120 240 Low 20 50 NOTE: Estimated pedestrian crossing volumes are based on the distribution of intersections in the combined data sets for Toronto and Charlotte. The estimated pedestrian crossing volume represents the sum of the pedestrian crossing volumes for all intersection legs. UNSIGNALIZED INTERSECTIONS The unsignalized intersection methodology in the second draft of HSM Chapter 12 (25), based on Equation (3) in this report, and the factors for three-leg STOP-controlled (3ST) and four-leg STOP-controlled (4ST) intersections presented in Table 7 of this report, should remain unchanged. ROADWAY SEGMENTS The roadway segment methodology in the second draft of HSM Chapter 12 (25), based on Equation (6) in this report and the factors for roadway segments presented in Table 8 in this report, should remain unchanged. CALIBRATION Calibration issues for the HSM methodologies are being addressed as part of the HSM production work in NCHRP Project 17-36. Therefore, no specific calibration methodology has been included in the draft HSM chapter. A decision will need to be reached in Project 17-36 as to whether the pedestrian safety methodology for signalized intersections developed as part of this research will be calibrated separately or will be calibrated as shown in Equation (1) as part of the overall predictive methodology. REVISED HSM DRAFT The second draft of HSM Chapter 12, presented in the Phase I and II report for this research (25), has been revised to incorporate the changes to pedestrian safety prediction methodology for signalized intersections presented above. A third draft of HSM Chapter 12 incorporating the pedestrian safety prediction methodology was presented in the draft version of this report. This third draft has been further revised in response to review comments and a fourth draft of HSM Chapter 12 is presented in Appendix A of this report.
61 In addition to incorporating the revised pedestrian safety methodology, the fourth draft of HSM Chapter 12 has been updated in response to review comments on the earlier drafts. All comments from the NCHRP project panel and many comments from other reviewers have been considered. Some comments raise issues beyond the scope of this research or that need to be handled in coordination with other HSM chapters. In particular, there are several issues that need to be addressed consistently across the three predictive methodologies in HSM Chapters 10, 11, and 12. These issues will need to be addressed in the HSM production work in NCHRP Project 17-36.
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