Study On Vehicle Emissions Reduction In Urban Traffic Network

According to the Intergovernmental Panel on Climate Change (IPCC) 2007 report, urban transport accounted for 13.1% of total global greenhouse gas emissions, which are the third-largest emitting sectors. In recent years, with the contradictions between traffic demand and traffic supply have become increasingly prominent, traffic pollution and energy consumption are increasingly grim situation at home and abroad,and which have begun to attach importance to the traffic environment evaluation and control. The urban road network of a node, a certain section of a regional environmental impact assessment has become essential, how to bridge the gap in transportation and emission models for the evaluation of dynamic traffic simulation ;combined traffic simulation tool to evaluate motor vehicle emissions, spatial and temporal distribution characteristics of traffic flow through the rational organization of the existing transport facilities in the same situation to improve road traffic environment, and reduce vehicle delays.Select light-duty car, mid-sized car and bus as the study object, how to optimize the traffic control measures to reduce emissions and delays as the research goal, firstly building a real-time on-board emission measurement system, through the actual driving conditions emissions tests, different types of motor vehicle emissions and the corresponding operating conditions database can be got, then comparing the emissions differences of four road types; through the vehicle emission factor analysis to determine VSP-based emission model which cover the speed, acceleration and road gradient; integrating the micro-emission model with dynamic traffic simulation tool to evaluate motor vehicle emissions of road network ,and get different types of motor vehicle emissions contribute to the situation; determining single transformation and signal timing optimization as two kinds of optimization of traffic control measures for the selected region, thereby re-organize the operation of traffic flow conditions, combined with traffic simulation tool to assess their environmental and social benefits. The study includes five aspects:1. The actual road motor vehicle transient emission test data acquisitionThe key of this work is to build a real-time on-board emission measurement system, collecting speed, latitude and longitude from the GPS system, collecting instantaneous mass emission of three kinds of emissions (CO,HC,NOx) second-by-second through OEM-2100, engine intake air temperature and pressure, engine speed, load can be got through engine operation condition monitoring systems. Four different grades of road were selected in vehicle emission test, through multiple tests in the actual operation state, establishment of second-by-second emission data and the corresponding driving conditions database; determining 22 parameters to describe the driving conditions characteristic of the four graded roads, and road vehicle driving characteristics were analyzed, the impact of speed on three kinds of emissions in four different graded road were compared. The results showed that: with decline of road grade, motor vehicles always operate at a lower speed range, while higher rates of CO and HC emissions, lower NOx emission rate. Increase in vehicle speed, to avoid the frequent acceleration and deceleration, reducing queuing time of vehicles crossing intersection and proportion of idle time, can effectively reduce the total vehicle emissions.2. Motor Vehicle Emission Model of Transient EmissionsThis work represents an attempt to bridge the gap in transportation and emission models, through the use of real-world distributions of Vehicle Specific Power (VSP) bins that are associated with speed, acceleration and road gradient, developing a micro-scale VSP-based modeling approach to estimate emissions. Integration of traffic simulation model and vehicle emissions model can be performed to quantitatively assess the impacts on environment from transport management and transportation planning. It not only provides technical support but useful guidance to evaluate the urban transport development subjected to environment improvement. Using the second-by-second instantaneous speed, acceleration and road gradient, VSP was computed from different vehicle types. The values were then categorized into 10 VSP Bins;The corresponding bin emission rate can be computed.3. Quantitative analysis and evaluation of regional transportation emission and delayIn this part, the hongqi street and yan'an street area were selected for simulation, Paramics Microscopic Traffic Simulation software was selected to build a road network topology map, using of Estimator module by traffic flow and turning flow to compute the OD data, determining the hot spots of emissions by the on road emission measurement data to optimize traffic control measures; through simulation software reliability analysis to determine the software can accurately describe the traffic situation in the region, and acquired regional traffic delay conditions; using of motor vehicles real-time operation data to compute the average mass emission rates by tracing vehicle operation in the simulation , integrated the VPS-based emission model with transportation model can be quantitatively evaluate the region's motor vehicle emission pollution conditions, and the benefits from appropriate emission control strategy.4. Study on regional emission reduction by single transformationThis section selected single transformation which fit the regional road structure and traffic characteristics as a regional transportation management and control means, through analyzing the pros and cons of clockwise and counter-clockwise organization of single transformation, select clockwise organizations as design; Yan'an Street, Hongqi Street, , Qinghua street and Wanbao Street were transferred from two-way access to one-way access, number of lanes remains the same, but also with the residents travel situation in Yan'an Street, Main Street and set up reverse bus lanes; using of Paramics traffic simulation software simulating the regional traffic flows after single transformation, combined with micro-emission model has been computed the total emissions. In contrast with before and after single transformation, the total hourly emissions reduced 4.62%. Compared the traffic delays before and after single transformation, building reverse bus lane and optimal design of time and space resources in intersection, vehicle speed increased by 17% or more, vehicle average delay decreased by 11% or more.5. Study on regional emission reduction by signal timing optimizationThe Hongqi Street - Yan'an Street region's main intersection were selected as an optimization target, using synchro signal timing optimization software, to conduct the signal cycle length, phase parameter optimization, the optimized results will be the input parameter of Paramics Software, select the simulated sample to calculate emission optimization classified by vehicle types and hourly total emission reduction, and compared before and after the optimization of traffic signal timing delays. By contrast the emissions before and after signal timing optimization, 7.93% of total emissions are reduced, indicating that through the optimization of signal timing to increase traffic capacity of the regional transportation will still be effective on the improvement of regional emissions. Through the optimization of signal timing can improve the vehicle speed of more than 14% at the same time can be reduced more than 25% of the delay time. It showed that through signal timing optimization can significantly improve the road environment as well as improve vehicle speed, reduce delays.Real-time on-board emission was used to build VSP-based micro-emission models, and their integration with dynamic traffic simulation tool to quantify regional emission situation; in coordination with regional road structure and the transformation states, single transformation and signal timing optimization were selected as two ways, there is no change of the existing transportation facilities through reasonable traffic organization, to improve environmental quality and reduce delays in the area. Research results have a good operability and practicality, not only useful on specific areas but also as emission optimization reference, while for effective and reasonable organization for urban traffic flow, there will provide theoretical support for our country's transport environmental governance have a positive impact .