on–road measurement of gaseous emissions and fuel consumption for two hybrid electric vehicles in Macao

Hybrid electric vehicles (HEVs) are promoted in China to ease increasing pressures of urban air pollution and oil security. In this paper, we measured two Toyota Prius HEVs by using a portable emission measurement system (PEMS) to evaluate their real–world performance with regard to gaseous emission factors and fuel consumption. Our results indicated that their average exhaust emission factors of CO, THC, NOX and CO2 were 0.25±0.08 g km–1, 0.015±0.002 g km–1, 0.009±0.005 g km–1 and 136±21 g km–1 (i.e., 5.81±0.90 L 100 km–1 for fuel consumption) respectively, while driving the averaged on–road traffic pattern. Compared to conventional gasoline and diesel vehicles, the tested HEVs demonstrated significant advantages in simultaneously mitigating major air pollutants (e.g., NOX), greenhouse gas emissions (CO2) and fuel consumption. For example, average CO2 emission factors are reduced by approximately 35% and 15% relative to conventional gasoline and diesel cars in Macao. Unlike conventional gasoline and diesel cars, relative CO2 emission factors of HEVs were much less sensitive to speed change, while their relative NOX emission factors were reduced as average speed became lower. This indicates significant environmental and energy benefits from HEVs under congested driving conditions. Our assessment suggests that HEVs are a competitive technology option for the taxi fleet in Macao with strong advantages in saving fuel cost for taxi drivers and mitigating NOX emissions.