Traffic Congestion and its Impacts on Greenhouse Gas Emissions: Can ITS Help?

Transportation plays a significant role in greenhouse gas emissions, accounting for approximately a third
of the United States’ CO2 inventory. In order to reduce CO2 emissions in the future, transportation policy
makers are looking to make vehicles more efficient and increasing the use of carbon-neutral alternative
fuels. In addition, CO2 emissions can be lowered by improving traffic operations, specifically through the
reduction of traffic congestion. This research examines traffic congestion and its impact on CO2
emissions using detailed energy and emission models and linking them to real-world driving patterns and
traffic conditions. It has been found that CO2 emissions can be reduced through three different strategies:
1) reducing severe congestion, allowing traffic to flow at higher speeds; 2) reducing excessively high
freeflow speeds to more moderate conditions; and 3) eliminating the acceleration/deceleration events
associated with stop-and-go traffic that exists during congested conditions. Details on several CE-CERT
research projects that directly address these strategies will be provided.