Assessment of Traffic Control Measures for the Reduction of Pollutant Emissions Using Traffic Flow Simulation
VORTISCH P, University of Karlsruhe, Germany
The emissions caused by motorised traffic are of growing concern within transporta- tion planning, and local authorities in Germany are now entitled to restrict traffic in areas where concentrations of certain pollutants exceed legally defined standards.
The emissions caused by motorised traffic are of growing concern within transporta- tion planning, and local authorities in Germany are now entitled to restrict traffic in areas where concentrations of certain pollutants exceed legally defined standards. The possibility of such traffic restrictions leads to a demand for control strategies that can be applied in such situations, and for tools that can be used to develop and assess these strategies. In our project we try to use the existing signal control infi'astrncture in order to relieve the emission situation of a critical area, that is an area defined as es- pecially sensitive to air pollution. Signal control can be used on the one hand side to reduce the traffic volume flowing into the area, and on the other hand side to control the remaining traffic in a way to minimise emissions.
Microscopic traffic simulation is an established tool for the development and assess- ment of signal control strategies, in particular traffic actuated signal control. Micro- scopic modelling is necessary to cover measures that are oriented on traffic situations at the level of single vehicles, e.g. public transport priority at signal controlled junc- tions. For the development of emission-minimal control strategies it would be helpful, if the existing microscopic traffic simulation tools provided also a computation of the emissions at the corresponding level of resolution in space and time. Such models for fuel consumption and pollutant emissions have been developed in the past (e.g. Benz 1984), but they depend on large amount of data for every type of vehicle to be simu- lated, typically they need an engine map for each pollutant component. This informa- tion is not available for the whole fleet of vehicles or at least for a representative sub- set of the fleet. On the other hand side, representative emission factors have been de- termined with high expenditure and published by the German Umweltbundesamt (i.e. the federal office for the environment), that can be used in principle to compute emis- sions from simulated traffic data (Hassel et. al. 1994). However, these emission data are published in a high degree of aggregation, so that a computation of emissions for a single trip of a single car is not possible, and the calculation procedure proposed by the Umweltbundesamt for the usage with the emission factors (Hoepfuer et. al. 1995) is not sensitive enough for the assessment of measures whose impacts do not exceed certain thresholds. For example, the positive effects of a slightly improved signal timing at a junction normally will not be reflected by the standard assessment proce- dure proposed for the emission factors.
In our project we had an practical and a methodical objective: On the practical side some hints for developing emission-minimal traffic control in critical areas were to be found. In order to do this, the methodical objective was to develop a tool for the de- velopment and assessment of signal control strategies by combining microscopic traffic flow simulation and representatively determined emission factors. As a con- crete example an area in the city of Mannheim (a German city with about 300.000 inhabitants) was selected and modelled in the simulation system.
WARDMAN M, BRISTOW A and HODGSON F, University of Leeds, UK
Association for European Transport