Combining road safety and traffic operations: An integrated approach to implement system-wide transportation improvements

Rapid increases in Saudi Arabia's vehicular traffic are challenging its urbanized road networks' safe and efficient operation. Facing both physical and economic constraints, transportation planning stakeholders in the country are seeking alternative methods for improving traffic operations and safety systemwide that do not rely upon infrastructure expansion. Using a sector of the Dammam metropolitan area in Saudi Arabia as the study area, we proposed and evaluated a comprehensive, integrated approach to improve both traffic system operations and safety in this urbanized road network. A combined route choice and control modeling framework was used to evaluate the potential systemwide benefits of concurrent driver information regarding the best available route and traffic signal control enhancements to facilitate operational improvements. Benefits were quantified as improvements in total systemwide travel times and reduction in total systemwide delays. To evaluate associated road safety improvements, a comprehensive road safety audit (RSA) was performed in the study area and Highway Safety Manual crash prediction methods were applied to estimate the potential reduction in crashes. Results indicated that concurrent driver information and an upgrade to vehicle-actuated traffic signal controls could improve total systemwide travel time by 22% and reduce the total systemwide delay by over 50%. If appropriate remediation measures are taken to address issues identified during the road safety audit, crashes could be reduced by up to 50 % per year at selected intersections. The study results infer that road safety improvements should be an integral part of any broader traffic systems improvement process and that the concurrent consideration of both traffic system operations and safety could provide the best return on investments. Further research could identify additional variables for consideration in the proposed comprehensive, integrated traffic systems improvement process and evaluate the transferability of this approach using a larger road network than the one considered in this study.