To check the regulated emission limits, mass emissions test for a vehicle is
conducted on a chassis dynamometer following a driving cycle. However, the
driving cycle and laboratory test are different from the real-world driving.
This article presents a study conducted on a mid-size gasoline car on chassis
dynamometer as well as on-road (real-world). It determines the effect of
real-world driving, different drive modes (idle, acceleration, deceleration and
cruising) on vehicle emissions and fuel consumption and their comparison with
the laboratory data. The emissions tests were conducted on the chassis
dynamometer following the Modified Indian Driving Cycle and on the selected
traffic routes in Dehradun city using a Portable Emission Measurement System
(OBS-2200). It was observed from the study that average on-road emission rates
in gram per second were 1.35 to 2.39 times higher for CO, 1.12 to 1.39 times
higher for CO2, 2.04 to 2.32 times higher for NOx and 2.17 to 5.0
times higher for THC as compared to the chassis dynamometer test. The test
results indicated that the on-road fuel consumption was higher than the
dynamometer test by 22.3%, 19%, 13.9% in congested, medium and low traffic
routes respectively. The low-speed conditions with frequent stop and go
operation, particularly on the congested roads, were the main reasons that
aggravated the vehicle emissions and fuel consumption in real-world driving
conditions. The time spent in various drive modes and percentage contribution of
the drive modes to vehicular emissions and fuel consumption were calculated and
analyzed using a computer program developed for the study. This study was also
an attempt to generate and understand the real-world vehicle emissions and fuel
consumption data in a Tier-II Indian city, and to establish the correlation
between the real-world vehicle emissions and emissions data generated in the
laboratory as per the legislative procedure.