Many roads in the Netherlands, especially in the densely populated area in the western part of the country, are congested in, and sometimes also outside, peak hours. Congestion has many adverse effects: loss of valuable time affecting road users most directly. Many traffic management measures have been introduced over the last years to reduce delays. These measures are often assessed in detail, not only with respect to delays. Effects on the environment are also important: do the measures result in decreased levels of emissions, noise, etc.? These are, however, difficult to quantify for traffic management measures. Emission factors for different pollutants (expressed in g/km traveled) generally only make a distinction between road types, not between traffic types. It is widely assumed that in a congested situation, vehicles produce more emissions than in calmer traffic. Also, at high speeds (>100 km/h), emissions rise sharply. Today, many motorways in the Netherlands have induction loops in the road surface at regular intervals, measuring speeds and traffic volumes. This offers possibilities for a more detailed analysis of emissions resulting from different traffic conditions. Also, there was a need to evaluate the many traffic management measures implemented on the Dutch motorway network. This was the reason for the Dutch Ministry of Transport and the Ministry of Housing, Spatial Planning and the Environment to commission a study into the possibilities of establishing different emission factors for different traffic conditions. The study consisted of two main elements: deriving emission factors for different traffic conditions, and applying these factors to detailed traffic data from specific road sections to calculate total emissions.
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