The Influence of Stops on Vehicle Fuel Consumption in Urban Traffic

A simple linear relation between fuel consumption per unit distance, ϕ and trip time per unit distance T, ϕ = k₁ + k₂T is established for the fuel data collected in Austin and Dallas, Texas, and Matamoros, Mexico. The qualities of traffic service in these cities are compared through the study of the spread of the data points along the ϕ, T trend, showing that the Matamoros data in general have higher ϕ and T values. The fuel consumption model ϕ = k₁ + k₂T is improved by the addition of a term proportional to ΔN_s(T), the deviation of the number of stops for a given datum point from the average number of stops associated with the trip time interval into which the datum point falls. It is shown in the resulting new model, ϕ = k₁ + k₂T + k₃ΔN_s, that since T and ΔN_s are virtually uncorrected, the values of k₁ and k₂ in the simpler model remain unchanged. A discussion of the physical interpretation of the model parameters is presented. In addition, an analysis of data obtained in central London shows that k₁ depends almost entirely on vehicle mass. It is also shown that the value of the parameter k₃ is approximately given by the product of the warmed-up idle fuel flow and the average stop duration.