One hundred and seventy-seven in-use Australian vehicles have been tested on a chassis dynamometer and it has been found that their fuel consumption, hydrocarbon emission rate and oxides of nitrogen emission rate are linearly related to the vehicles' instantaneous power demand. On-road power demand models have been developed which have been tested for an individual vehicle and shown to give trip fuel consumption to within 2 per cent for moderate length trips (10 km) and to within 9 per cent for short trips (0.3 to 1.8 km). The basic power demand model has been extended using detailed vehicle map data so that it may be used to give accurate microtrip (100 M or less) fuel usage estimates. The only vehicle parameters required for the use of either the basic or the microtrip power demand models are engine capacity, engine type (spark or diesel), vehicle mass and vehicle on-road drag as a function of velocity. The only road data required is the vehicle velocity profile and road gradient. Vehicle maps from which the power demand models were developed are presented for specific vehicles and the fleet averaged vehicle. In addition, unsteady state fleet averaged (and specific vehicle) engine maps are presented. These have been constructed from our chassis dynamometer data and they may be used to predict the effect of variations in vehicle design parameters, or traffic flow patterns on any vehicle's on-road or on-dynamometer fuel consumption. For abstracts of separate papers included in the report see TRIS nos. 378222-225. (Author/TRRL)