Vehicular Emission Modeling at Toll Plaza Using Performance Box Data

Abstract

Delay occurring on any facility causes an extra amount of fuel consumption, leading to extra emissions. Toll plazas are the points laid on the highways for toll transaction that act as bottlenecks on highways. Vehicles must slow down from their stream speed for paying the toll and again accelerate to attain their desired speed. During this whole operation, vehicles join the long queue and frequently accelerate to take the position of leader vehicle when the vehicle in front of the queue leaves the tollbooth. The vehicles in the queue are in the static engine-on condition. Such operation causes intense vehicular emission. This study aims to quantify the emission characteristics at attendant operated toll plazas under mixed traffic conditions using instantaneous data of speed and acceleration. In order to collect the field data, the performance box (P-Box) instrument is used. A discretization of speed profile (DOSP) method was developed for the present study. A zone of influence (ZOI) is found out by statistical analysis which covers 250 m length upstream and downstream from a tollbooth that includes the zone of deceleration and zone of acceleration. The ZOI is further divided into 50 m sections to record the tail-end emission. The international vehicle emission (IVE) module based on vehicle specific power (VSP) is used for emission modeling. The analysis is carried out first for the whole ZOI and then for each section of 50 m for accurate estimation of the zone of the maximum pollution level. Two cases, one with a toll plaza (TP) section and other non-toll plaza (NTP) section, are considered. The IVE is used to model the pollutants, such as carbon monoxide (CO), volatile organic compounds (VOCs), particulate matter (PM), nitrogen oxides (NOx), and sulphur oxides (SOx). The result shows that the maximum emissions are observed when the vehicle is in idling condition in a zone of waiting and a zone of transaction. Further, the emission rates at the TP section is found to be an average of 40% more than the NTP section. It is anticipated that with the automation of attendant toll collection (ATC) to electronic toll collection (ETC) will decrease the idling cycle, thus reducing the emission level at toll plazas. Further, the present research may be useful to proposed emission-based congestion pricing policy at toll plazas in peak hours.