The publication by AASHTO of the first edition of the Highway Safety Manual (HSM) is an important step forward in providing safety analysis tools for highway agencies. In particular, HSM Part C includes predictive methods that can be used by transportation agencies to anticipate the safety performance of new facilities, to assess the safety performance of existing facilities, or to estimate the expected effectiveness of proposed improvements to existing facilities. However, the first edition of the HSM does not address all facility types of potential interest to transportation agencies. HSM Chapter 12 provides a predictive method for two and four lane urban and suburban arterial facilities with both undivided and divided cross sections. Two facility types that are not addressed in the existing chapter are arterials with six or more lanes and one-way arterial streets. A task force of the AASHTO Subcommittee on Safety Management has reviewed research needs and identified the omission of these facility types as one of the more significant gaps in the first edition of the HSM. Research is needed to develop safety prediction methods for these facility types.
The objectives of this research are to (1) develop a predictive method for use in the HSM to address crash frequency and severity for both roadway segments and intersections on arterials with six or more lanes and one-way arterial streets and (2) provide procedures that will assist transportation agencies to consider safety in decisions related to these facilities during widening and modifying existing arterials or designing new facilities. The scope of the research will be limited to urban and suburban highways and streets other than freeways.
Accomplishment of the project objectives will require at least the following tasks.
(1). Review Chapter 12 of the HSM and its prediction method, related IHSDM tool and spreadsheet, and related research. Review the guiding principles established for HSM development and available guidance concerning measures of safety, research protocols, and other applicable topics. (2). Prepare a working paper presenting the anticipated attributes of the prediction models for six or more lanes and one-way urban and suburban arterials and how the results would work with Chapter 12 of the HSM. Discuss analytical improvements that are possible to attain under this project. Document the importance of each attribute and explain it in terms of decision needs of practitioners and data availability, among other factors. (3). Conduct a GOTOMEETING conference call with the project panel to discuss the Task 2 working paper.
(4). Based on Task 3 project panel feedback, prepare a detailed work plan to develop and validate the prediction models for the following facilities:
One-way Arterial Streets and Intersections
- Determine availability of or ability to obtain crash, traffic, and roadway inventory data for 2, 3, 4, or more lane one-way arterial streets including intersections. Consider the need for pedestrian and bicycle data.
- Recommend the type and number of models needed to create prediction models for use in the HSM. One or more models may be needed to account for 2, 3, 4, or more one-way arterial lanes and intersections.
Six or More Lane Arterial Streets and Intersections
- Determine the availability of or ability to obtain crash, traffic, and roadway inventory data for 6 or more lane arterial streets and intersections.
- Recommend the type and number of models needed to modify, extend, or develop models to use with the current HSM Chapter 12.
(5). Prepare an interim report providing the results of Tasks 1 through 4. The interim report should also include a revised Phase II work plan that describes how the needed data will be collected and the models developed and validated. (6). Meet with the project panel to review the Task 5 interim report approximately 1 month after its submittal. Submit a revised interim report addressing the panel’s review comments for approval by NCHRP. NCHRP approval is required to proceed with Phase II.
(7). Execute the approved Phase II work plan to develop and validate the prediction models. (8). Develop proposed chapter sections with examples and modified Appendix A of the HSM. The chapters will be provided to TRB Highway Safety Performance Committee for review in parallel with the project panel.(9). Develop a Microsoft PowerPoint presentation that can be used for training, including trainer’s notes and a spreadsheet for application of the new models.(10). Conduct a pilot workshop with the project panel using the PowerPoint presentation developed in Task 9 to demonstrate the application of the models to practical examples. Revise the presentation based on the panel’s review comments. (11). Prepare a final report documenting the entire research effort including recommendations for additional research that will be needed to enhance the models (citing specific study protocols, data collection alternatives, appropriate analysis techniques, and potential policy implications). The proposed chapters and revised Appendix A developed in Task 8 shall be included as appendices to the final report.
Beta testing completed; See NCHRP 17-71
for follow-up on activity.