Abstract Emissions, fuel economy, and performance are determined over a light and a heavy driving cycle designed to represent the vehicles in-use driving patterns. The vehicles are 2010 class 8 Freightliner tractor trucks equipped with Cummins engines with Selective Catalytic Reduction and Diesel Particulate Filter emission control systems. The hybrid has lower carbon dioxide emissions, better fuel economy, and nitrogen oxide emissions statistically the same as the conventional. The CO emissions are well below the standards for both vehicles, but they are higher from the hybrid. The higher CO emissions for the hybrid are primarily related to the cooling of the Diesel Oxidation Catalyst (DOC) during the standard 20 minute key-off soak between repeats of the driving cycles. With a 1 minute key-off soak the CO emissions from the hybrid are negative. The relevance of higher hybrid CO emissions to in-use emissions is not clear since it is not known how often or how long the engine is off between deliveries on a typical day. The measured hybrid particulate emissions are statistically the same for the heavy cycle but higher for the light cycle. The higher PM for the hybrid may be related to the cooling of the DOC during the 20 minute key-off soak. Performance is measured by determining the time to accelerate on the chassis dynamometer to 20 mph for each cycle. The hybrid takes longer to reach 20 mph and accelerates slower than the conventional. Introduction Hybridization of vehicles is being pursued to reduce exhaust emissions, reduce petroleum fuel consumption, and reduce greenhouse gas emissions. The most common hybridization method is to employ a battery powered electric motor in parallel or in series with the petroleum powered motor.The goal of the present study is to evaluate the performance of a conventional class 8 truck and two hybrid class 8 trucks for emissions, fuel economy, and acceleration rate from 0 to 20 mph. The conventional truck and one of the hybrids are used to deliver product in the Los Angeles, California area. The second hybrid is a newer, slightly higher horsepower model used by Freightliner to demonstrate their latest hybrid technology. The standard regulated emissions, fuel economy, and acceleration rates are discussed in this paper. Most prior studies comparing hybrids to their conventional counterparts have measured higher nitrogen oxide (NO x) emissions from the hybrids. In this study the measured hybrid NOx emissions were statistically equivalent to the conventional NOx emissions. Literature Search Over the last 15 years there have been several evaluations of battery electric medium to heavy-duty gasoline or diesel hybrids [ 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 , 12, 13] West Virginia University [ 1] measured the emissions and fuel economy of six buses over six different emission test cycles having average speeds from 3 to 17 mph and duty cycles from 4 to 18 stops per mile. Three of the buses were powered by Compressed Natural Gas (CNG), one by 1998 DDC Series 50, diesel, one by 1998 DDC Series 30 diesel and an Orion VI hybrid, and one by a 1998 DDCVMM 642 DI diesel and a NovaBUS RTS Hybrid. Depending upon the test cycle, in comparison to the DDC Series 50 diesel, the Orion VI hybrid CO emissions range from 56% to 99% lower, the NO x from 6% higher to 44% lower, the CO2 from 5 to 40% lower, and the fuel economy from 6 to 64% better. Equivalent comparisons for the NovaBUS RTS hybrid were: CO emissions 67 to 95% lower, NOx emissions 7% higher to 18% lower, CO2 emissions 8% higher to 23% lower, and fuel economy from 11% worse to 21% better.Emissions, Fuel Economy, and Performance of a Class 8 Conventional and Hybrid Truck2015-01-1083 Published 04/14/2015 Robert L. Russell, Kent Johnson, and Thomas Durbin Univ. of California Patrick P. Chen Jasna Tomic and Richard Parish Calstart CITATION: Russell, R., Johnson, K., Durbin, T., Chen, P. et al., "Emissions, Fuel Economy, and Per