Developing Analysis, Modeling, and Simulation Tools for Connected Automated Vehicle Applications: Traffic Optimization for Signalized Corridors—Case Studies in Ann Arbor, MI, and Conroe, TX
Traffic Optimization for Signalized Corridors (TOSCo) is a series of innovative connected and automated vehicle applications designed to optimize traffic flow and minimize stopping on signalized arterial roadways. Real-time infrastructure information about queues and traffic signal operations are used by TOSCo equipped vehicles to plan and control their speeds to enhance mobility and reduce emissions across the corridor. This study investigated the mobility and environmental benefits of deploying TOSCo in one low and one high-speed corridor. The low-speed corridor was the 3.9-mile-long Plymouth suburban corridor, located in Ann Arbor, Michigan, which consisted of 11 intersections (nine arterial and two freeway interchanges). The high-speed corridor was the 12-mile-long stretch of SH 105, located in Conroe, Texas, which consisted of 15 intersections. Microscopic simulation models of the two selected suburban corridors were used to examine the potential mobility and environmental benefits of using TOSCo under different market penetration rates.
An off-the-shelf microscopic simulation tool with advanced programming interface capabilities was selected to support the development and assessment of TOSCo functionality. Performance measures used for evaluating mobility benefits were total delay, stop delay, number of stops, average speed and total travel time. For evaluating environmental benefits, carbon dioxide emissions and energy usage rates were selected.
- TOSCo produced substantial reductions in stop delays and the number of stops in both corridors. TOSCo implementation decreased stop delay by 40 percent in the low-speed corridor and by 80 percent in the high-speed corridor. TOSCo did not cause substantial changes in the total delay experienced by travelers in both corridors.
- The TOSCo system produced similar mobility benefit trends in both low- and high-speed corridors. For example, the total delay, stop delay, and the number of stops decreased by 8.69 percent, 41.80 percent, and 28.69 percent, respectively, in the east bound direction at 100 percent penetration rate. At 100 percent TOSCo penetration rate, the total delay, stop delay, and the number of stops decreased by 3.35 percent, 27.22 percent, and 13.05 percent, respectively in the west bound direction of the low-speed corridor. TOSCo produced more benefits when volume-to-capacity ratio was higher.
- Enabling TOSCo on the through movements of the main approach improved the overall traffic condition that increased the mobility benefits from non-TOSCo approaches as well.
- TOSCo did not have a substantial impact on vehicle emissions or fuel consumption, although TOSCO had minor reductions in hydrocarbon (HC) and Nitrogen Oxides (NOx) in each corridor. Emissions benefits in the low-speed corridor were more sensitive to smaller changes in speed.
- Results from both corridors showed that TOSCo was less effective at low-traffic volume and low-delay intersections. When the traffic volume was low, or signal coordination provided good progression, most vehicles did not need to stop or slow down at the intersection, which left very limited space for TOSCo to adjust vehicle trajectories.