Research Report
John N. Ivan, Sha Al Mamun, Nalini Ravishanker, Bhagwant Persaud, Craig Lyon, Raghavan Srinivasan, Bo Lan, Sarah Smith, Taha Saleem, Mohamed Abdel-Aty, Jaeyoung Lee, Ahmed Farid, and Jung-Han Wang
Jan-21
This report describes efforts to develop improved crash prediction methods for crash type and severity for the three facility types covered in the 2010 Highway Safety Manual (HSM)—specifically, two-lane rural highways, multilane rural highways, and urban/suburban arterials. For each, models were estimated for undivided and divided (multilane rural and urban/suburban only) segments and three- and four-leg stop-controlled intersections and four-leg signal-controlled intersections (also three-leg signal-controlled intersections for urban/suburban arterials). The models use data for segments and intersections with “base conditions” that are defined specifically for each facility type. Only the observations that satisfy the defined base conditions were used for estimating these models. For urban/suburban arterial segments, because no sites met all base conditions for roadside fixed objects and median width, these variables were included in the models only if considered appropriate for that crash type and if the variable was statistically significant in the model and with the expected direction of effect. For some crash types, the number of driveways was also directly included in the models where warranted. These base condition models provide predictions that can be adjusted for actual conditions at a place of prediction, such as lane and shoulder width, the presence of lighting, and other pertinent factors. Content describing these models and instructions for applying them has been prepared for inclusion in the second edition of the HSM. A revisit of the HSM’s procedure for calibrating prediction models for transfer to other jurisdictions is also described and recommendations for updating that procedure offered. Average condition models were also estimated using all available valid data points available from the state data used for each facility type; these are provided in an appendix.
NCHRP Web-Only Document 295: Improved Prediction Models for Crash Types and Crash Severities
Arterial highways
Crash severity
Crash types
Driveways
Four leg intersections
Mathematical models
Mathematical prediction
Multilane highways
Multiway stop signs
Rural highways
Signalized intersections
Three leg intersections
Two lane highways
HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.
A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.
Research reports are often summarized in executive summaries, technical briefs, or other abbreviated formats. Included here are those road safety summaries that involved research using HSIS data.
In addition to conducting research, HSIS resources are also used to develop products that can be used by practitioners in the analysis of safety problems.
HSIS data are sometimes used in research studies that result in other types of finished products, such as dissertations, theses, and conference proceedings.
