| The Asian Games and Asian Games for the Disabled were held in Guangzhou during November and December in 2009. In order to ensure the air quality, Guangzhou government has begun to implement traffic control measures to vehicles ever since pre-Asian Games. Traffic control changed the vehicle operating modes, thereby affected the vehicle emission characteristics and total emissions. In this background, this paper took Guangzhou for example during the exercise of traffic control and carried out on-board emission tests on LPG transit buses of Guangzhou using PEMS before and after the traffic control. Vehicle operating modes, emission factors and other characteristic parameters were obtained from the sample buses and the differences of operating modes and emission characteristics before and the after traffic control were analyzed. Base data of LPG buses in Guangzhou was obtained through investigation and statistical analysis, and Guangzhou LPG transit bus total emissions calculation model was established based on the MOVES model. Finally, total emissions of Guangzhou LPG transit buses were calculated before and after the traffic control.In this study, on-board emission tests were conducted on four different bus routes on four LPG transit buses using SEMTECH-DS PEMS. And two of the sample buses meet state Ⅱ emission standard and the other two meet state III.92605valid sets of test data were obtained and the accumulated mileages reached 413.5km. Based on the PEMS results, the distribution characteristics differences of speed, acceleration and VSP were analyzed before and after the traffic control. At the same time, the influences of speed, acceleration and VSP to emission were analyzed by comparison.Based on the data of LPG transit buses operating modes obtained by PEMS, combined with the base data such as LPG transit buses population, annual mileage, age distribution, road type distribution, meteorology information and other parameters, the MOVES model was modified and Guangzhou LPG transit buses calculation model was established. And then total emissions of Guangzhou LPG transit buses were calculated before and after the traffic control. The results and conclusions indicated as follow:(1) Through statistics and analysis, the average speed of sample buses was 12.20km/h before traffic control and reached 16.82 km/h after traffic control, increased by 27.48% than before.(2) During the traffic control, the proportion of idle decreased 6.28%, while the proportion of steady speed increased slightly.(3) No matter before or after the traffic control, the VSP of Guangzhou LPG transit buses range was small, mainly ranged in [-2,1)kW/t.(4) The emission factors of CO、HC and NOx decreased with the increase of speed and its degree of decline decreased with the increase of speed. And the average emission factors of CO、HC and NOx were reduced by 18.47%,13.39% and 12.96% respectively after the traffic control.(5) The relationships between acceleration and emission rate of CO, HC and NOx were similar. The emission rates were relative low in the deceleration stage, and in the acceleration stage that became higher. The emission rates of CO and HC were smaller after traffic control than that before, and NOx was bigger.(6) At the negative VSP range, emission rates of CO, HC and NOx changed relatively gentle, and they dropped to the lowest value when VSP was close to 0. At the positive VSP range, emission rates of CO and HC began to increased and then decreased, while emission rate of NOx increased monotonously with the increase of VSP.(7) Estimated the total annual emissions of CO, HC and NOx from Guangzhou LPG transmit buses before and after the traffic control using the localized MOVES model. The total annual emissions of the three pollutants after the traffic control were approximate 496.31 tons,924.75 tons and 17308.35 tons respectively, which decreased 20.59%,12.65% and 11.42% than before. And the effect of traffic control measures was significant. |
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