Environmental pollution in Urban Transportation NetworksIn the past decades, extensive research efforts have been made in the area of urban environment striving to improve the urban air quality and address the challenges emerged from public health and the preservation of the entire ecological system. Transportation-related emissions are the dominant source of urban air pollution, and the second largest source of carbon dioxide (CO 2 ) emissions in the United States, which emitted approximately 27 percent of total U.S. greenhouse gas (GHG) emissions in 2015 (Figure 1). Transportation has also been the fastest-growing source of GHG emissions. From the pre-industrial era (i.e., ending about 1750) to 2015, concentrations of the greenhouse gases (CO 2 , CH 4 , and N 2 O) have increased globally by 44 percent, 162 percent, and 21 percent, respectively [1].The greenhouse gas (GHG) emissions primarily come from burning fossil fuel for all modes of transportation (vehicles, ships, trains, and planes) [2]. Petroleum based fuel took over 90 percent for transportation, including gasoline and diesel fuels. Most of the transportation related GHG emissions are carbon dioxide (CO 2 ) emissions resulting from the combustion of petroleum-based fuels. More than 50 percent of transportation related GHG emissions are from passenger vehicles, lightduty trucks, sport utility vehicles, pickup trucks, and minivans. Other portions of GHG emissions are from heavy-duty trucks, commercial aircraft, ships, boats, trains, pipelines, and lubricants.In addition to GHG emissions, transposition also makes contributions to important air pollutants (68.4 percent CO, 60 percent VOCs, 49.1 percent NO x , 5.5 percent particulates and 1.3 percent SO 2 ) [3][4][5]. Moreover, NO x is not only a primary air pollutant, but also accounted for the production of free radicals in troposphere, which can promptly react with VOCs and lead to a large variety of secondary air pollutants that could be much more hazardous to the public health than the primary air pollutants in urban environments [3][4][5]. Dirty air has been linked to cancer, asthma, stroke and heart disease, among other health issues. In UK, roughly 40,000 deaths each year can be attributable to outdoor air pollution [6,7]. Curbing vehicle emissions has become an increasingly important task in urban environment.
Monitoring and Strategies to Reduce Transportation EmissionsIn response to these challenges, a range of emerging technologies are adopted to reduce transportation-related emissions on urban roadway networks. Existing traffic monitoring networks enable adaptive traffic
AbstractThis article reviewed the impacts of vehicle emissions in urban transportation network, the existing strategies to reduce such transportation emissions, the complexity of urban transportation environment network, and the development of vehicle emission models. The vanguard research needs are also proposed in developing emission and air quality models and simulation, and emission-oriented transportation management strat...