The “Truck in the Park” project was a jointly funded research project which demonstrated the benefits of the use of biodiesel in a tourism related industry. The National Park Service (NPS) operated a truck in Yellowstone National Park (YNP) for 149,408 km (92,838 miles) on 100% biodiesel fuel produced by the University of Idaho. Participants in this project included Montana Department of Environmental Quality, Wyoming Department of Commerce, NPS, Department of Energy's Regional Biomass Energy Program, Koch Agri-Services, Dodge Truck, Cummins Engine Company, J.R. Simplot, Western States Caterpillar, University of California at Davis, and the University of Idaho.This summary report details the fuel production, engine performance, durability, and engine emissions tests performed on the test vehicle.The test vehicle was a 1995 Dodge 2500 four-wheel-drive pickup with a Cummins B 5.9 liter turbocharged, direct injected, diesel engine. Chassis dynamometer tests showed that the vehicle did not experience a reduction in power over time. Oil analyses, compression, injector tests, and engine and fuel pump teardown inspections also indicate that the engine did not experience excessive wear or deterioration as a result of using biodiesel as a fuel. The durability was considered equivalent or better than diesel fuel. Emissions tests were performed at the beginning (1995) and end (1998) of the project. Results from these tests indicated HC and CO decreased and PM increased as the percentage of rapeseed ethyl ester (REE) was increased. NOx generally decreased as the percentage of REE was increased. Fuel use increased by 14% from 1995 to 1998. Cold start emissions data was limited, but it shows that HC, CO, and PM seemed to increase more for diesel cold starts than biodiesel cold starts compared to hot starts with the same fuel. 149,408 km (92,838 miles) of use with 100% biodiesel did not affect the efficiency of the catalytic converter.