A large-scale experiment has been carried out by INRETS to identify actual vehicle-use conditions. Fifty-five privately-owned cars were equipped with sensors and data acquisition systems and studied under actual use conditions with their own drivers. Vehicle and engine speeds, engine and ambient temperatures, and fuel consumption were recorded at one-second time intervals over 71,000 kilometres and 9,900 trips. The data obtained yielded very accurate information on the actual car use and operating conditions: daily vehicle use, trip characteristics (trip length, duration, and so on), speed and acceleration profiles, engine running conditions (engine speeds, choke use, etc), and thermal conditions, while taking into account the influence of the vehicle type, driver behaviour and geographical location. Vehicles uses were very frequent (5 to 6 trips per day) and often short: one trip in two did not exceed three kilometres. Time spent at rest or at low speed was very significant. The uses were highly diversified according to the drivers and the areas of origin of the vehicles studied. The results are compared to those obtained during a driving diary survey conducted by INRETS. Significant discrepancies are to be observed concerning trip lengths and vehicle-use frequencies. The INRETS on-board measurement method is described and discussed, including its specificity, its advantages, and its limits. (A)
Abstract