The Spatial Variability of Vehicle Densities as Determinant of Urban Network Capacity

Amin Mazloumian (), Nikolas Geroliminis and Dirk Helbing

No CCSS-09-009, Working Papers from ETH Zurich, Chair of Systems Design

Abstract: Due to the complexity of the traffic flow dynamics in urban road networks, most quantitative descriptions of city traffic so far are based on computer simulations. This contribution pursues a macroscopic (fluid-dynamic) simulation approach, which facilitates a simple simulation of congestion spreading in cities. First, we show that a quantization of the macroscopic turning flows into units of single vehicles is necessary to obtain realistic fluctuations in the traffic variables, and how this can be implemented in a fluid-dynamic model. Then, we propose a new method to simulate destination flows without the requirement of individual route assignments. Combining both methods allows us to study a variety of different simulation scenarios. These reveal fundamental relationships between the average flow, the average density, and the variability of the vehicle densities. Considering the inhomogeneity of traffic as an independent variable can eliminate the scattering of congested flow measurements. The variability also turns out to be a key variable of urban traffic performance. Our results can be explained through the number of full links of the road network, and approximated by a simple analytical formula.

Keywords: Urban traffic; network dynamics; congestion spreading; macroscopic traffic model; fundamental diagram (search for similar items in EconPapers)
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Citations: View citations in EconPapers (44)

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