Highway Research Record

VI. RESEARCH WORK DONE IN ACADEMIC INSTITUTIONS RELATED TO THESIS WORK
C. TRAFFIC AND TRANSPORTATION
Evaluation of Signal Interruptions on Vehicular Emissions

Date of Start:August 2004
Indian Institute of Technology, Madras (R, C)

Scope and Objective
(i) To conduct field tests to measure tail pipe emissions from selected vehicles under two scenarios - interrupted and      uninterrupted movements through a series of signals on an arterial road (case study).
(ii) To analyse the field data to estimate the total vehicular emissions for test runs under interrupted and uninterrupted      conditions.
(iii) To compare the emissions of test vehicles under the two scenarios and to evaluate the reductions in emissions for       uninterrupted flow vis-à-vis interrupted flow.
(iv) To conclude, based on the above objectives, on the general merits of synchronisation of a series of signals in a traffic       corridor.

Methodology
This study is mainly intended to evaluate the influence of signal interruptions on vehicular emissions. For this purpose, the tail pipe emissions (at source) and instantaneous speeds of three different vehicles (two wheeler, three wheeler and four wheeler) were measured under interrupted and uninterrupted movements through a case study corridor in Chennai city. A portable Gas Analyser was used for measuring tail pipe emissions and an optical sensor for measuring instantaneous speeds of test vehicles. Field data was analysed to evaluate the reductions in emissions of test vehicles when they followed uninterrupted flow.

Findings and Conclusions
(i) Interrupted 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 18% CO, 26% HC and 21% NO, based on average values per run along the test     corridor.
(ii) For three-wheeler test vehicle, the percentage reductions in emissions for uninterrupted flow (as compared to interrupted     flow) in the direction of Thousand Lights Mosque to Tarapore Towers were CO – 18%, HC - 26, NO – 21%, and in the     reverse direction these were 17%, 15%, and 13%, respectively.
(iii) For four-wheeler test vehicle, the percentage reductions in emissions for uninterrupted flow (as compared to interrupted     flow) in the direction of Thousand Lights Mosque to Tarapore Towers were CO – 14%, HC – 12%, NO - 15%, and in the     reverse direction these were 11%, 11%, and 10%, respectively.
(iv) For two-wheeler test vehicle, the percentage reductions in emissions for uninterrupted flow (as compared to interrupted      flow) in the direction of Thousand Lights Mosque to Tarapore Towers were CO – 16%, HC – 20%, NO – 18%, and in the      reverse direction, these were 15%, 13%, and 17%, respectively.

This study is an attempt at quantifying the reductions in emissions due to smoothing of traffic flow through a traffic corridor, using a case study.  Though only three-test vehicle were used, the study has brought out the potential for pollution mitigation through synchronisation of signals, though indirectly. This study has also established the feasibility of using Gas Analyser measurements to collect tailpipe emissions.

Further tests on more vehicles using more case studies will shed further light on the merits of synchronisation of signals.  Simulation approach can also be adopted to evaluate such benefits for a variety of scenarios.