| Title | A study on the relation analysis between energy consumption, emissions and transportation planning (2/2) |
| Dept | Transportation Planning and Land Transport Division |
| Year | 2009 |
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| Summary | From the perspective of transportation planning, this project explores the feasibility of developing an “integrated evaluation framework” (IEF) which is capable of incorporating dynamic performance of vehicle energy consumption and emissions into the aggregate sequential travel demand model. Departing from the traditional mainstream which estimates vehicle fuel consumption and emissions on a trip-base, with parameters of distance, i.e. l/km or g/km, from a laboratory bag-stock test, we approach it in terms of g/sec with a link-specific correlation of traffic flow speed. It can be easily integrated into the link-base travel demand model as a new attribute of the highway network. Therefore it is capable of providing distinctive fuel consumption and emissions of varying traffic demands. Eventually, integrated with the correlations, the IEF shall turn out to be an analytical tool which enhances sustainability evaluation of transportation planning. In the first two years, as the pioneers of a long term study, we utilized test vehicles equipped with On-Board Emissions Measurement to gather second-by-second data of fuel consumption and emissions from on-road surveys. Likewise, designed analogous laboratory tests are performed to collect corresponding data to build up relationships with statutory standard test results published by BoE, MOEA and EPA. Major achievements of the first two years are listed as follows: The “integrated evaluation framework” (IEF) is proposed. The correlations of vehicle energy consumption and emissions are conceptually assumed, and statistically proofed, as functions of link speed. It is incorporated into the aggregate sequential travel demand model as a network link attribute. On-road surveys of 7 kinds of link-category of two vehicles, as well as analogous laboratory tests, are performed to form up the dataset of over 310,000 records. With the dataset, look-up tables of speed v.s. fuel consumption and 4 emission rates (CO2, CO, THC and NOx) are provided for each vehicle of link-category in terms of g/sec. Two models of dynamic correlation function are investigated. Both models are statistically confident in estimating fuel consumption and CO2 emissions with traffic flow speed. (1) Model 1: correlation functions are directly derived from on-road surveys for each vehicle. (2) Model 2: correlation functions are developed from the speed-relevant compound conversion rate to statutory published data. The compound conversion rate is composed of a series of conversion rates of which each represents the condition difference of a pair of tests. All conversion rates are appropriately fitted as functions of speed. Two case studies are presented to demonstrate how to integrate into transportation planning model and to validate the operability and accuracy of two models of dynamic correlation functions. It is concluded that the accuracy of estimated fuel consumption and CO2 emission of both models is highly acceptable to transportation planning model. In addition, in terms of g/sec, emission analysis of urban arterial can be easily performed without the necessity to cut up intersection sections from links. |
| Post date | 2009/07/16 |
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