Real-World Carbon Dioxide Impacts of Traffic Congestion

Abstract

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 shortterm 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 of the congestion analysis is developed, followed by real-world congestion analyses. BACKGROUND

An Inter-vehicle Communication Based Cooperative Speed Suggestion Algorithm for Smoothing Fluctuations in Stop-and-go Traffic

“…A significant amount of pollutant emissions and fuel consumption are made due to traffic oscillations including high acceleration, congestion and stop-and-go conditions [2]. It has been found that by reducing traffic oscillations, especially eliminate frequent acceleration and deceleration events associated with stop-and-go traffic that exists during congested conditions, CO 2 emissions can be reduced by up to 20% [3].…”

A review of recent research on green road freight transportation

“…The CMEM for heavy-goods vehicles was developed and presented by Scora and Barth (2006), Barth et al (2005) and Barth and Boriboonsomsin (2008). It is based upon second-by-second tailpipe emissions data collected from 343 light-duty vehicles (LDVs) tested under a variety of laboratory driving cycles.…”

Urban Freight Truck Routing under Stochastic Congestion and Emission Considerations

“…Obviously, the amount of vehicle emissions per mile depends on vehicle speed. For example, the minimum CO2 emission rate occurs when the vehicle speed is around 45 to 50 mph, while a very high or a very low vehicle speed would lead to a much larger amount of CO2 emission [3]. Thus, maintaining a moderate travel speed throughout a journey would help reduce vehicle emissions, although it usually increases total traveling time.…”

“…According to Sjodin et al [2], CO and NOX emissions from vehicles increase substantially in congested traffic, causing adverse effects on air quality and human health. In addition, greenhouse gases such as CO2 emission from vehicles also increases greatly when roadway is severely congested, which plays a significant role in global climate change [3]. As such, vehicle emissions in congested urban areas and their environmental impacts should be carefully addressed.…”