Emissions and vehicle kilometres by type of road in the Netherlands, 2002
Of the total number of car kilometres in the Netherlands, approximately 30% are travelled in built-up areas; oxides of nitrogen are mainly formed on motorways, where engine temperatures are high.
Most emissions in built-up areas
Carbon monoxide (CO), volatile organic compounds (VOCs, excluding methane) and to a lesser extent particulate matter (PM10) are mainly emitted by road vehicles inside built-up areas. One reason for this is driving style (frequent acceleration and braking); the other is the effect of cold engines. The latter is particularly relevant for vehicles with catalytic converters, since they only start to operate when the engine is warm.
Most emissions on motorways
Nitrogen oxides (NOx) are mainly formed at high engine temperatures, and therefore at high speeds (on motorways, for example). The use of three-way catalytic converters (for petrol and LPG engines) and exhaust gas recirculation (for diesel engines) have considerably reduced NOx emissions. A more detailed explanation of the causes of emissions is given elsewhere.
See also: Emissions to air by Traffic and transport in the Netherlands, 1990-2002*, for a description of the causes of the various emissions.
See also: Air quality alongside traffic routes in the Netherlands, 1990-2002
