The use of a roadside remote sensing device to encourage voluntary vehicle emissions related maintenance

The control of emissions from the road fleet is increasingly dependant on sophisticated engine management systems and after treatment components. Failure of these systems and components results in individual vehicle emissions levels far in excess of those which could be attained. The mitigation of these excess emissions has the potential to assist Local Authorities in achieving the National Air Quality Strategy targets and save the individual car owner money from reduced fuel consumption. This study has used a roadside remote sensing device (RSD) to measure the emissions of vehicles passively in the traffic stream. The RSD unit reported the measured emissions in terms of emissions efficiency by comparing the quantity of a specific pollutant (CO, HC or NO) to the quantity of fuel being burnt (using CO2 as a proxy) in the measured vehicle’s trailing exhaust plume. The RSD system also captured the measured vehicle’s registration number. This record was combined with the vehicle’s speed and acceleration immediately before measurement of its emissions. Using previously defined emissions efficiency thresholds relating to vehicles suspected of having an emissions related fault, the number of gross polluting vehicles in Winchester was ascertained. This was a very small proportion of all measured (0.2 to 0.4% depending on the pollutant); although the percentage of excess emissions attributed to these vehicles was higher (2-4%) it was still not particularly large. To make use of RSD measurements and encourage owners of gross polluting vehicles to repair their vehicle, a number of emissions measurement feedback strategies were examined using a questionnaire survey. These feedback mechanisms were: i) use of a roadside variable message sign (VMS); ii) use of a website database/VMS; iii) provision of a subsidised emissions check, and iv) diversion to a Park and Ride site. It was concluded that the most successful strategy would be the use of a roadside VMS with support of a website plus use of email/phone SMS notification. A high percentage of respondents indicated they would submit their vehicle for a voluntary emissions check under such circumstances (~95%). The provision of a subsidised check would remove an observed reluctance to those owning older cars to have their vehicle checked although a hardcore (~4%) of respondents would not have their vehicle checked voluntarily under any of the scenarios. In less affluent areas with an older vehicle population such an approach could result in significant emissions savings from the local vehicle fleet and so have beneficial implications for the health of the local community due to improved air quality.