The Highway Safety Manual (HSM) 1st edition provides analytic tools and techniques for estimating the effect of changes to the roadway environment on motor vehicle crash frequency, but provides almost no information on their effects on pedestrian and bicyclist crash frequency. NCHRP Project 17-84, “Pedestrian and Bicycle Safety Performance Functions for the Highway Safety Manual,” is in the process of developing crash modification factors (CMFs) and safety performance functions (SPFs) for pedestrians and bicyclists in support of a future HSM 2nd edition. However, NCHRP Project 17-84 is not comprehensive, and the safety benefits of many (especially newer) pedestrian and bicycle countermeasures will still be unknown after the project is completed. Furthermore, established CMFs focused on vehicle-vehicle collisions do not properly account for possibly adverse safety effects for pedestrians and bicyclists or others outside of the vehicle. In addition, the HSM’s CMFs for roadway lighting generally require updating. Without quantifiable safety prediction methods, it can be difficult to justify countermeasure installation, compare and contrast different countermeasure options, or evaluate tradeoffs in vehicular and multimodal safety (e.g., as part of road cross-section reallocation efforts).
The objective of this research is to develop a guide that will include consideration of how treatments focused on addressing the safety or operational needs of one set of roadway users may have different effects on travelers with vision or mobility impairments. Crash-reduction performance is highly important, but not the only factor governing decisions about the specific countermeasure(s) to be installed at a given location. Other guidance documents (e.g., NCHRP guides on pedestrian analysis (NCHRP Research Report 992: Guide to Pedestrian Analysis) and roadway cross-section reallocation (NCHRP Web-Only Document 318: Safety Prediction Models for Six-Lane and One-Way Urban and Suburban Arterials)) will discuss bigger-picture trade-offs involved in decision-making and can be used in conjunction with the findings from this study for countermeasure selection.
The objectives of this research include quantifying (1) the safety performance (crash-reduction effects) of pedestrian and bicyclist safety countermeasures and (2) the pedestrian/bicyclist crash reduction (or expansion) effects of vehicle safety countermeasures, specifically focusing on the highest-priority countermeasures not addressed by NCHRP Research Report 992 or NCHRP Web-Only Document 318.
Potential tasks include (1) reviewing findings and recommendations from previous research; (2) identifying future research priorities for developing CMFs and SPFs for pedestrian and bicyclist safety countermeasures; (3) conducting a focused literature review on relevant new research (4) prioritizing needs for additional CMFs and SPFs for pedestrian and bicyclist safety countermeasures, as well as new methodologies to predict ped/bike safety outcomes, based on what is available and what is still needed; and (5) preparing a data collection plan (including surrogate safety measures) for selected countermeasures, that will maximize the potential that the project will develop CMFs and SPFs with high-enough ratings for eventual inclusion in the HSM.
Estimating the safety performance of countermeasures and their impacts on bicyclists and pedestrians is critically important to improving safety. The outcomes from this study can inform agencies about the safety performance of various countermeasures and will help them make data-driven decisions regarding treatments to improve bicyclist and pedestrian safety.