The Traffic Flow Analogy to Compressible Fluid Flow

摘要

The flow of vehicles in one lane of traffic offers a striking analogue to the flow of a compressible gas in a constant area duct. In order to arrive at a suitable descriptive model for traffic, however, one must assume well behaved drivers whose training or instinct makes them conform to a pattern sufficiently homogenous to allow analytic description. For a gas composed of molecules that are not required to associate too intimately, a thermodynamic state equation in the form P = (rho)RT is usually used. (P = pressure, (rho) = density, R = gas constant, T = temperature). For the simplest case of uniformly moving traffic wherein 1 denotes the spacing between vehicles and L the length of the vehicle, the state equation in terms of vehicle density (vehicles per mile) under the uniform conditions is: (rho) = 5280/(1 + L) where 1 and L are in feet. Vehicular spacing, 1, will vary with vehicular speed, V. (Author)