Assessing The Effects Of Transit Signal Priority Strategy On Vehicle Emissions On The Basis Of Microscopic Simulation

In recently years, the provision of priority for public transit has become a hot topic in big cities for the purposes of alleviating traffic congestion and protecting environment. Methods to provide priority for public transit, such as exclusive bus lanes and bus rapid transit, have developed rapidly, while transit signal priority has drawn more and more attentions of researchers from home and abroad. Previous research has shown that transit signal priority can improve vehicle operations like delay and travel speed. However, it could not be neglected that transit signal priority can play a positive role in creating a green transportation environment.This thesis aims to assess the effects of different transit signal priority scenarios on vehicles emissions in the entire network. It analyzes the effects of different transit signal priority scenarios on vehicle emissions from three aspects:emission characteristics from time perspective, emission characteristics from space perspective and total emissions. The results will provide the theoretic basis for traffic operators when they develop environmentally-friendly strategies on transit signal priorities.To this end, in this thesis, specific power equations suitable for China light duty gasoline and heavy duty diesel vehicles and the VSP clustering method have been chosen based on transit signal priority and vehicle emission theory. After emission data of vehicles in Beijing in real road conditions is collected with portable emission measurement system (PEMS), the emission rate of every VSP interval for all vehicles is determined based on the ratio of traffic composition. Then an emission prediction model which reflects the actual traffic behavior is proposed and its accuracy is tested.The corridor of BRT Line2in Beijing is taken as a case study. A VISSIM based traffic simulation platform is used. Driving behavior parameters based on Genetic Algorithm’ are calibrated and emission estimation oriented precision test is conducted. Moreover, an isolated actuated and coordination control strategy under large-scale and complex road network, scheme in which regular bus and BRT vehicle share the same lane under signal priority control strategy and pre-signal actuated control strategy for transit signal priority at isolated intersections are designed.. Finally, the changes of traffic behavior under different transit signal priority scenarios are analyzed and the effects of different transit signal priority scenarios on vehicle emissions are evaluated from three aspects: emission characteristics from time perspective, emission characteristics from space perspective and total emissions. The results show that bus emissions can be reduced effectively while car emissions increases and the influence on total emissions depends on specific traffic conditions after the implementation of transit signal priority.