Creative Utilization of Urban Roadway Facilities with Predictive Safety Assessment Tool – Phase 1
For better and safer roadways with widening or dividing the roadway with a median barrier, one needs to know if the number of crashes will increase and decrease in future and how many are actual increase or decrease. Everyone wants to drive safely and efficiently on a newly built roadway, and it is important to plan ahead if current or future roadway experience fewer or more crashes from an engineering study.
This engineering study will bring benefit for the safety engineers and policymakers to make an educated decision before building or modifying the current section of road. In addition, this study will help them to understand how much traffic in new roadways will affect number for crashes and types of crashes.
This engineering study looked at the safety of road users – how many crashes are expected to be experienced under given conditions – numbers of vehicles and road geometry. With roadway improvements, for example, an increasing number of lanes, building a median/raised barrier to separate the traffic, if there is a decrease or increase in the crashes and types of crashes. This study also shows if we control the number of vehicles with the increase or decrease – how that will increase or decrease the crashes on that particular section of roadway.
The road users in the community, using the section of the roadway on daily basis, will experience with such improvements in safety while they drive. For proper balance between increasing traffic with building new road is difficult for the engineers and decision makers. This study will help to make decisions with numbers and justification (data-driven approach).
Research Project Highlights
The objective of this project was to develop a predictive safety assessment tool (PSAT) based on the Highway Safety Manual (HSM) predictive methodology and principles by comparing the safety performance of existing facilities to improved conditions of proposed facilities. The major highlights of this tool development under Phase I includes:
- predictive safety tool of converting existing facility to proposed facility with improvement in urban/suburban arterial systems considering geometric, operations and traffic parameters
- User-friendly dashboard of safety performance of existing and proposed (improved) facility in urban/suburban arterial systems with crash frequency by severity and crash types
- Sensitivity analysis for impact of traffic on safety performance of existing and proposed (improved) facility in urban/suburban arterial systems
This assessment tool is intended to enable safety researchers, engineers, and transportation planners at the agency level to understand and quantify the impact of safety improvements. This phase of the study (Phase I) focused on the development of a simplified framework of the safety assessment tool in a Microsoft Excel environment to evaluate the safety impacts of converting one type of existing facility to another (for example, 2-lane undivided to 4-lane divided, 4-lane undivided to 4-lane divided, 3-lane undivided to 5-lane undivided, 6-lane divided to 8-lane divided facilities, etc.) as well as the impacts of improvements to specific geometric elements in urban settings. The project demonstrated the user/analyst understanding of the impact of a set of improvement projects relative to the existing condition at a quantitative scale. Input for this tool included data regarding road geometry features, traffic (Annual Average Daily Traffic, AADT), and other existing land use information. This Excel application provided a simplified framework for converting one type of facility to another by inputting and selecting traffic exposure, existing geometric conditions, and unit length of corridor (i.e., one mile of corridor length). The tool is expected to assist in evaluating existing and proposed facilities from the outcome of analysis in the form of predicted crash frequency and distribution of collision types by injury severity level. In addition, it provides a notion of impact of traffic volume on predicted crashes by types.
Dr. Islam shared his experiences about the tool development via CUTR webcast: Urban Roadway Facility Conversion with The Predictive Safety Assessment Tool: An Application of the Highway Safety Manual.