Real-World Carbon Dioxide Impacts of Traffic Congestion

Although these options look promising, they are unlikely to make a great impact in the near term. Some of them (e.g., fuel-cell vehicles) are still in their early stages of technology development and probably will need a dramatic breakthrough before they can be fully implemented. For those that are technology-ready and have started to enter the market (e.g., hybrid vehicles and alternative fuels), it will still probably take several years for a majority of the existing fleet to be turned over before a significant impact on CO 2 can be seen. That being said, it can be pointed out that comparatively little attention has been given to CO 2 emissions associated with traffic congestion and possible short-term CO 2 reductions as a result of improved traffic operations. Traffic congestion can be considered as a supply management problem. The transportation infrastructure (i.e., roadways) can be considered as supply for use by drivers (demand). If these supplies are limited in terms of capacity and demand is high, congestion is likely to occur. Several studies have shown that roadway congestion is continuing to get worse. For example, the Texas Transportation Institute (TTI) conducts an urban mobility study that includes estimates of traffic congestion in many large cities and the impact on society (3). The study defines congestion as " slow speeds caused by heavy traffic or narrow roadways or both due to construction, incidents, or too few lanes for the demand. " Because traffic volume has increased faster than road capacity, congestion has become progressively worse despite the push toward alternative modes of transportation , new technologies, innovative land use patterns, and demand management techniques. It is commonly known that as traffic congestion increases, CO 2 emissions (and in parallel, fuel consumption) also increase. In general , CO 2 emissions and fuel consumption are sensitive to the type of driving that occurs. Highlighted as part of many " eco-driving " strategies , traveling at a steady-state velocity will give much lower emissions and fuel consumption compared with a stop-and-go driving pattern. By decreasing the stop-and-go driving that is associated with congested traffic, CO 2 emissions can be reduced. However, it is not clear to what degree various congestion mitigation programs will affect CO 2 emissions. CO 2 emissions are examined here as a function of traffic congestion. After some background information on modeling tools and traffic information data used for analysis, the basis …