20. Modelling Vehicular Emissions under Heterogeneous Flow
Date of Start

January 2004
Indian Institute of Technology Madras (R, C)


Scope and Objectives

The overall objective of this research is to study the influence of various traffic parameters as prevailing in heterogeneous traffic on tail-pipe emissions, with particular focus on the impact of lane following.

The specific objectives of this work include:
• To conduct field tests on select vehicles under varying conditions and measure tail-pipe emissions.

• To analyze the collected data and evaluate the influence of various parameters on emissions, with particular focus on lane-following/lane-less movement.

• To develop models that will relate tail-pipe emissions with traffic variables.

The scope of the present work is limited to measuring on-road tail-pipe emissions (CO, HC and NO) using a portable gas analyzer for three types vehicles. These include petrol-driven two-wheelers, three-wheelers and four-wheelers of different ages. The case studies are conducted on four road sections of one to three km lengths in Chennai city.

The crux of the methodology is on field measurements of tailpipe emissions of selected vehicles while they traverse a mid-block section under varying conditions. The data required for the study includes pollutant concentrations, instantaneous speeds and fuel consumption during each test run. A Gas Analyser with exhaust probe attached to the tail pipe of the vehicle measures the pollutant concentration and an optical sensor with data logger assembly measures instantaneous speeds. These are measured for the study vehicles (two-wheelers, three-wheelers and four- wheelers of different ages). The test vehicles are run on the different study stretches of varying distances, with the instruments fitted. Each pass is taken as one test run. Fifteen to thirty runs are made for each of the vehicles in each of the cases of lane following and lane-less movement. Data were obtained in the form of pollutant concentrations for emissions and RPM of the wheel for instantaneous speed. The pollutant concentrations are converted into total emissions for each run. Thus, the total pollutants and speed data for test runs for different conditions are obtained. From this, the percentage reduction in emissions for lane following conditions vis-à-vis lane-less movement is evaluated. Further, the interest here is also to model the relationships of vehicular emissions to vehicular speed, fuel consumed, accelerations and decelerations, distance travelled, and number of lane changes. For this, regression models for each category of vehicles are developed.
Findings and Conclusions
Lane-less flow conditions generally produce higher levels of tail-pipe emissions of CO, HC and NO. The data collected in this study indicate reductions of upto 72% HC, 58% CO and 70% NO, based on average values per run along the test stretch.