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This research was performed to experimentally determine how the amount of fuel used to accelerate an initially stationary vehicle to a constant cruising speed depends on acceleration level. Initially stationary vehicles were accelerated at different rates to a constant cruising speed on a test track, and the amounts of fuel used to travel a fixed distance from the starting point were measured. By subtracting the amount of fuel that would have been required to travel this same distance at the cruising speed from the measured amounts, estimates of the additional fuel used to accelerate from standstill to the cruising speed were obtained. These estimates were then examined as a function of acceleration level, which was characterized by the time taken to reach the cruising speed. Tests were conducted for cruising speeds of 48 km/h, 64 km/h and 80 km/h. Factors investigated included different vehicles (8 in all), engines (L-4, V-6, V-8), and fuels (gasoline and diesel).

Speed-time data obtained in two large-scale studies by following randomly selected vehicles in a number of cities with an instrumented car are analyzed here by dividing the data into trip segments between successive stops and computing values of traffic variables for the individual trip segments. Results from the two studies are found to be in good agreement. The analysis focuses on variables previously shown to be related to fuel consumption, particularly on the relationship between energy used to accelerate the vehicle, energy dissipated in braking, and mean traffic speed. Braking and acceleration are found to play a major role in determining tractive energy requirements in low speed urban driving, since about half the energy supplied to the wheels is used to accelerate the vehicle, and about two-thirds of the resulting kinetic energy is dissipated in braking.