Factors affecting particulate matter levels near highway toll plazas in India

Abstract

Toll plazas are expected to have elevated levels of particulate matter (PM). However, this study through simultaneous measurements at two kerbside highway locations, reveals that PM concentration is higher at around 500 m from the toll plaza. This may be due to higher particulate emissions from vehicles while accelerating/ decelerating mode. Real-world driving approach was adopted using onboard emission monitoring instruments to find particle number concentration in the exhaust during different operating conditions. Subsequently, dispersion analysis was done using US EPA’s AERMOD, which complied with the measurements. Further, relationship between PM levels with traffic and meteorology was also investigated and found that traffic flow had a significant positive effect on PM. Measurements at toll plazas with different geometries divulged that staggered geometry plazas are expected to have highest PM concentration. Lastly, the analysis of PM ratios revealed that contribution of exhaust emissions in overall emissions increases near the toll plaza.