Burke, Andrew (2004) Present Status and Marketing Prospects of the Emerging Hybrid-Electric and Diesel Technologies to Reduce CO2 Emissions of New Light-Duty Vehicles in California. Institute of Transportation Studies, University of California, Davis, Research Report UCD-ITS-RR-04-02
In the case of the modern diesel engines, it was found that such engines have much higher toque characteristics than gasoline engines of the same displacement and vehicles powered by diesel engines have higher fuel economy (mpg) by 40-50% than similar (same size and performance) vehicles powered with gasoline engines. This is the reason that diesel-powered vehicles have presently reached almost a 50% market share in Europe. The major problem with the diesel engine for use in California is that "so-called clean" diesel powered vehicles have NOx emissions that are still 10X higher than Tier 1 vehicles with gasoline engines and to meet the SULEV NOx standard, a reduction of at least an additional factor of three is required. Whether this will be possible with diesel engines is uncertain.
Hybrid-electric passenger cars are currently being marketed in Japan and the United States by Toyota and Honda. These hybrids show large improvements (at least 30-50%) in fuel economy compared to conventional ICE vehicles of the same size and performance. All the hybrids meet SULEV emission standards and have been designated AT-PZEVs by CARB. The hybrids have been well received in the market with annual global sales approaching 100,000 in 2004. There seems to be no reason that hybrid sales will not continue to increase between 2005-2010 especially as the ZEV Mandate requirements become more demanding in 2008 and beyond.