Speed Limits on Motorways

From 2008 to 2009
For the Federation for a Better Environment (Bond Beter Leefmilieu), TML did a small study to estimate the effects of a change in maximum allowed speed on motorways in Belgium. The study looked at the effects on travel times, emissions of PM10, NOx and CO2, and on traffic safety. Three variants were studied: a change in maximum speed for passenger cars from 120km/h to 100km/h, to 110km/h and to 130km/h.

In a first step, the effect of a change in maximum speed on actual speeds on the roads was estimated. Measurements of traffic on Belgian motorways in 2007 were used. Based on traffic flow theory, the effect on speed was estimated for each data point.
Then the effects on travel times, emissions and traffic safety were estimated, based on these changed data points.

The results for Belgium can be found in the table below. This table indicates the difference in costs and benefits, compared with the reference situation (a maximum speed of 120 km/u). Negative figures show a decrease of costs, positive figures an increase.

Combining travel times, emissions and road safety, a reduction of the speed limit to 110 km/h gives the most benefits: a reduction of the costs to society with 36 million euro/year.

Due to the high costs of the increase travel times, lowering the maximum speed towards 100 km/h gives a smaller benefit than one would achieve with 110 km/h.

Increasing the speed limit to 130 km/h leads to negative effects: the travel time costs reduce, but the emissions and road safety costs increase largely.


From 2008 to 2009


Bond Beter Leefmilieu



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Filip Vanhove