The prospect that the real cost of transport fuel will continue to rise emphasises the need for conservation. Driver characteristics and vehicle efficiency are two important determinants of vehicle fuel consumption. An experiment was set up on the Small Road System at TRRL to examine these two factors in particular, and also to examine the contribution made to fuel consumption by other factors such as vehicle speed and passenger load. Five cars were used in the experiment, one of which was a diesel of similar performance to one of the petrol cars. Visitors to Open Days 1979 were asked to drive round a test circuit, once in a normal way and then, in a way they considered to be an economical way of driving. The results showed that drivers could save more than 20 per cent of fuel by driving economically (one in five gallons). In general the saving was accompanied by a reduction in mean vehicle speed, but independent of speed differences, a saving of 14.7 per cent was achieved by economical driving. The diesel car used 25 per cent less fuel than the equivalent performance petrol car when driven normally, and 34 per cent when the cars were driven economically. An extra passenger increased fuel consumption by 2 to 6 per cent. There was little difference between the average fuel economy returned by men and women drivers, although men drivers tended to give more varied results. Multiple regression analysis showed speed to be the main factor which influenced fuel consumption.(A)

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