Addressing elevated vehicle emissions in Flanders

Remote sensing to detect and prevent elevated emissions of road vehicles

In the second part of the study, a remote sensing system, developed by HEAT, was used to measure the on-road emissions of a large sample of vehicles. Measurements were performed at 5 locations in Flanders and this was the first time such measurements were performed under highway conditions. Many new insights into the on-road emission performance of vehicles were gained and the main conclusions were:

• A small group of vehicles with high emissions account for a disproportionate share of total emissions.
• Remote sensing can effectively detect problems (manipulations, failures, maintenance problems) with exhaust after-treatment systems, which increases the effectiveness of police and inspection tasks.
• Using a remote sensing system during roadside checks can substantially increase the detection rate of emission problems.
• Detecting problems with diesel exhaust after-treatment systems using remote sensing is most effective on highways where emission levels are normally low.
• Remote sensing campaigns conducted in the past on urban and rural roads do not provide a complete picture of vehicle emissions performance.
• The effect of ambient temperature on vehicle emissions is limited and observed differences can be traced back to rush hours in the morning and afternoon as underlying cause.