Abstract
The efficient movement of users and goods is the primary purpose of the surface transportation system. Roadway traffic crashes have devastating impacts on quality of life of the users as well as health of the system. While researchers are utilizing advanced computing and communication tools to reduce number of crashes on the roadways, there is still an absence of appropriate method to evaluate the safety performances of these advanced technologies in the planning stage. Development of crash modification factors (CMFs) is a standard method to evaluate the safety effect of proposed countermeasures. Though, the current practices of developing CMFs are not efficient and cost-effective in case of addressing impacts of Intelligent Transportation System (ITS) countermeasures. This study demonstrated a proof of concept of simulation-based framework for determining CMFs for ITS countermeasures. The proposed framework includes the application of traffic microsimulation model and Surrogate Safety Assessment Model (SSAM) developed by Federal Highway Administration (FHWA). The integration of these two models is suggested to estimate CMFs efficiently. However, the calibration of traffic microsimulation model and SSAM model is essential to portrait the real-world scenarios. A case study for estimating CMFs of ITS countermeasures was conducted to validate the proposed simulation-based approach. Four ITS countermeasures were considered: ramp metering, variable speed limit, junction control, and dynamic lane assignment. They were coded in traffic microsimulation environment and vehicle trajectory files were generated to import into SSAM model. After analyzing these trajectory files in SSAM tool, it was found that all proposed ITS countermeasures, except variable speed limit assignment, could reduce the number of crashes at crash prone locations.
Highlights
The traffic fatality rate on United States highways and freeways presented a declining trend from 2006 to 2014 after deploying safety initiatives, such as mandatory seat belt use and strict law imposition against driving under influence of drugs
While researchers are focsuing on parameters such as crash types and severity [8], roadway types [9], different socioeconomic conditions [10], and time changes [11] to investigate the variability of crash modification functions (CMFs), variables such as vehicle types, driver ages and characteristics, and weather conditions have not been examined so far [12]
The implementation of countermeasures could demand a huge amount of investment, and once it is built, additional money could be wasted to undo in case of errors that may increase the number of traffic crashes
Summary
The traffic fatality rate on United States highways and freeways presented a declining trend from 2006 to 2014 after deploying safety initiatives, such as mandatory seat belt use and strict law imposition against driving under influence of drugs. In HSM, a catalog of safety performance functions (SPFs) and crash modification functions (CMFs) for different geometric and operational countermeasure types is included to predict safety performance of any facility [5]. While researchers are focsuing on parameters such as crash types and severity [8], roadway types [9], different socioeconomic conditions [10], and time changes [11] to investigate the variability of CMFs, variables such as vehicle types, driver ages and characteristics, and weather conditions have not been examined so far [12]. The duration of study for developing CMFs is another drawback, in that the research process requires data of traffic crashes before and after implementation of countermeasures. Installation of ramp meter on multilane highway could cost approximately 1 million excluding right of way acquisition
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