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Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2023. Pedestrian and Bicycle Safety Performance Functions. Washington, DC: The National Academies Press. doi: 10.17226/27294.
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Page 1
Page 2
Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2023. Pedestrian and Bicycle Safety Performance Functions. Washington, DC: The National Academies Press. doi: 10.17226/27294.
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Page 2
Page 3
Suggested Citation:"Summary." National Academies of Sciences, Engineering, and Medicine. 2023. Pedestrian and Bicycle Safety Performance Functions. Washington, DC: The National Academies Press. doi: 10.17226/27294.
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1   The crash prediction models in Part C of the Highway Safety Manual (HSM) are most suited for estimating expected frequencies of multiple- and single-vehicle motor vehicle crashes, excluding pedestrian and bicycle crashes. With the exception of a comprehen- sive pedestrian safety prediction model for urban and suburban signalized intersections, the models in HSM Part C estimate pedestrian and bicycle safety based on the propor- tion of pedestrian and bicycle crashes to motor vehicle crashes. This generalized approach for determining site-specific estimates of pedestrian and bicycle crashes is not sensitive to site-specific conditions that influence pedestrian and bicycle crashes (including exposure and infrastructure) and provides little information for evaluating the site-specific effects of proposed projects intended to improve pedestrian and bicycle safety. Explicit consideration of pedestrian and bicycle safety, beyond urban and suburban signalized intersections, is critical for the implementation of future editions of the HSM. The objective of this research was to develop pedestrian and bicycle safety performance functions (SPFs) for transportation practitioners at all levels to better inform planning, design, and operations decisions. This included the development of pedestrian and bicycle SPFs for a wide range of site types including roadway segments and intersections in rural, urban, and suburban areas for potential incorporation into the HSM. To accomplish the research objective, three separate approaches to collecting data and developing pedestrian and bicycle SPFs for roadway segments and intersections were followed. Develop Pedestrian and Bicycle SPFs Incorporating Available Exposure Data for Pedes- trians and Bicyclists Using traditional crash-based modeling techniques (e.g., negative binomial regression analysis), pedestrian and bicycle SPFs were developed for urban and suburban roadway seg- ments and intersections, and the models incorporated both motorized (i.e., motor vehicles) and nonmotorized (i.e., pedestrian and bicycle) exposure measures. These SPFs were lim- ited to urban and suburban areas as this was where pedestrian and bicycle count data were available for model development. Pedestrian and bicycle SPFs were developed for the following site types: • Urban and suburban roadway segments – Two-lane undivided roads (2U) – Four-lane undivided roads (4U) – Four-lane divided roads (4D) – One-way roads (OW) (including one-lane, two-lane, and three-lane roads) • Urban and suburban intersections – Three-leg stop control (3ST 2×2) – Three-leg signal control (3SG 2×2) S U M M A R Y Pedestrian and Bicycle Safety Performance Functions

2 Pedestrian and Bicycle Safety Performance Functions – Four-leg stop control (4ST 2×2) – Four-leg signal control (4SG 2×2) – Four-leg signal control (4SG 1×2) Intersection configurations ending with (1×2) indicate an intersection between a one-way and a two-way roadway; configurations ending with (2×2) indicate intersections between two, two-way roadways. For each site type, three levels of models were developed, as appropriate: • A reduced model to estimate total pedestrian/bicycle crashes (i.e., all severity levels com- bined) that primarily includes exposure measures for motor vehicles and pedestrians/ bicycles. • An expanded model to estimate total pedestrian/bicycle crashes (i.e., all severity levels combined) that includes exposure measures for motor vehicles and pedestrians/bicycles as well as other geometric, traffic control, and site characteristic features, which were found to be significant predictors of total pedestrian/bicycle crashes. • A reduced model to estimate fatal and suspected serious injury (FS) pedestrian/bicycle crashes that primarily includes exposure measures for motor vehicles and pedestrians/ bicycles. The final pedestrian and bicycle SPFs and associated adjustment factors developed through this analysis were recommended for potential incorporation into the Part C pre- dictive method chapter for urban and suburban arterials and the Part B network screening chapter for the second edition of the HSM (i.e., HSM2). Develop an Approach to Pedestrian and Bicycle Crash Prediction for the HSM based on Procedures Implemented in the U.S. Road Assessment Program (usRAP) Pedestrian and bicycle SPFs were developed for rural two-lane roads, rural multilane highways, and urban and suburban arterials by adapting crash prediction models used by the U.S. Road Assessment Program (usRAP) (usRAP, n.d.) and its international partner the International Road Assessment Programme (iRAP) (iRAP, n.d.-b). The RAP models for pedestrian and bicycle crashes were developed for worldwide application and adapted in the current research to fit with U.S. highway safety practice and terminology and the format of the HSM. The final pedestrian and bicycle SPFs and associated adjustment factors developed by modifying the RAP models were recommended for potential incorporation into the Part C predictive method chapters for rural two-lane, two-way roads; rural multilane highways; and urban and suburban arterials of HSM2. Develop Models to Estimate Pedestrian and Bicycle Safety Performance Based on Crash Data in the Absence of Pedestrian and Bicycle Exposure Data Regression models were developed to estimate the potential of a pedestrian or bicycle crash occurring in the absence of having pedestrian or bicycle exposure data. In other words, no direct estimate of pedestrian and bicycle volume (e.g., daily volume, peak-hour volume, 2-hr count, etc.) along the roadway or at an intersection was included in the model development; however, other indirect measures of pedestrian and bicycle exposure (e.g., population) were included in the model development. Models were developed to estimate the potential of a pedestrian or bicycle crash occurring on various roadway segments and intersection types when pedestrian or bicycle exposure data were not available. Models were developed for rural roadway segments, urban and suburban roadway seg- ments, and urban and suburban intersections. Data from Ohio were used to develop models

Summary 3 for rural roads, and data from Minneapolis and Philadelphia were used to develop models for urban and suburban roadway segments and intersections. No models were developed for rural intersections. Specifically, models were developed that address the following site types: • Rural roadway segments – Two-lane undivided roads (2U) • Urban and suburban roadway segments – Two-lane undivided roads (2U) – Four-lane undivided roads (4U) – Four-lane divided roads (4D) – One-way roads (OW) (including one-lane, two-lane, and three-lane roads) • Urban and suburban intersections – Three-leg signal control (3SG 2×2) – Four-leg signal control (4SG 2×2) – Four-leg signal control (4SG 1×2) The results of this analysis are recommended for incorporation into the forthcoming new chapters on pedestrians and bicyclists and systemic safety management planned for HSM2. Three spreadsheet tools were developed and/or updated to incorporate the pedestrian and bicycle SPFs for use with HSM procedures. The spreadsheet tools are available on the National Academies Press website (nap.nationalacademies.org) by searching on NCHRP Research Report 1064.

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Each year, national crash studies have estimated that while overall traffic fatalities are decreasing, the percentages of those fatalities among pedestrians and cyclists are increasing.

NCHRP Research Report 1064: Pedestrian and Bicycle Safety Performance Functions, from TRB's National Cooperative Highway Research Program, presents state departments of transportation and other transportation professionals with an update of pedestrian and bicycle safety performance functions (SPFs).

Supplemental to the report are three spreadsheet tools that address SPFs on rural multilane roads, rural two-lane roads, and urban/suburban arterials.

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