Effectiveness Of Signal Coordination As An Emission Reduction Measure For Vehicles

Air Pollution is a significant health and environmental concern. Vehicular emissions are major contributors to many air pollution problems. There is growing interest in reducing carbon dioxide emission because of the alarming increase in the pollution caused by petroleum resulting global warming issue. Various studies have found that U.S vehicles emit half of the CO2 emitted from vehicle all over the world. Dallas Fort Worth is a non-attainment area for ozone and it is required to achieve NAAQS standards by 2010. NOx and VOCs from the automobile are a major precursor of ozone formation in the atmosphere. Traffic signal retiming has prove to be a beneficial measure for improving traffic flow conditions and reducing fuel consumption. This research focuses on measuring CO2 and NOx from light duty vehicles to verify the effectiveness of traffic signal synchronization as measure for reduction of emissions. Data for this research were collected using the On-Board Emission Measurement System OBS-1300. The OBS-1300 facilitates real-time collection of field data for second-by-second measurement of tailpipe emissions. The Chevy Astro Van was used as the study vehicle to collect on-road emission data on Cooper Street and involved four different drivers. The effect of signal coordination on CO2 and NOx pollutants and the relationship between different driving modes were investigated using statistical and graphical approaches. Rigorous statistical analysis has shown that the average emission rate for CO2 collected on peak hour on Wednesday was increased by 15.4% after signal retiming, emissions at other times did not significantly change. After dividing emissions into different velocity clusters for each mode, CO2 emissions were observed to increase for most of the velocity clusters after signal retiming. The analysis conducted for NOx emissions showed that after signal retiming, the emissions decreased for most of the velocity clusters. Since emissions by velocity cluster are a function of engine parameters only for a given velocity and acceleration, there should have been no difference in before vs. after. Ambient humidity or temperature could have caused the changes. The emission rates for CO2 in g/mile were highest for acceleration, followed by deceleration and then by cruise. In the case of NOx, the average emissions were highest for acceleration, followed by deceleration and then by cruise.