Considering the Environment and Safety in Signal Timing

More and more, transportation agencies are interested in perfomance measurement and mangement as a means to properly address issues related transportation systems. To date,  the performance measures used in assessing and optimizing signal timing have been limited to mobility measures, such as travel time and delays with very littel attention to the impact of traffic signals on the environment and safety. A research team from Florida International University (FIU) and the University of Florida (UF) comprised of Dr. Mohammed Hadi (FIU), Dr. Lily Elefteriadou (UF) and Dr. Yan Xiao (FIU) have set out to investigate and recommend methods for assessing and reducing adverse environmental and safety impacts associated with signal timing, in combination with mobility measures.

To estimate vehicle emissions, the research team has selected to use MOVES (Motor Vehicle Emission Simulator), which in recent years has produced accurate estimates. Combined with microscopic traffic simulation tools, MOVES can be used to estimate the quantity of different pollutant emissions based on the operating modes of vehicles. The traffic simulation model tracks each vehicle and records its speed, acceleration/deceleration rate, and location. Such information can be used to determine the operating modes of vehicles for use as input to MOVES to calculate the emission rates.  In terms of safety, the SSAM (Surrogate Safety Assessment Model) combined with microscopic simulation has been used to identify the potential conflicts in the network. 

This project utilizes emission and safety information generated based on microscopic simulation models combined with MOVE and SSAM to derive equations that estimate emission and safety performance based on macroscopic traffic characteristics.    These models are then used as part of a traffic signal timing process to optimize signal timing based on combinations of mobility, safety, and environmental measures.   This optimization takes into consideration the priority that the user places on these measures.

For more information on this project, contact Dr. Mohammed Hadi at or Dr. Lily Elefteriadou at