One of the measures to decrease the concentration of NO2 near freeways is to reduce the maximum speed from 120 or 100 km/h to 80 km/h. The effect is reasonably well-known in the Netherlands because of the introduction of this measure near Overschie (A13 Rotterdam) in 2002, accompanied by strict enforcement. Given the positive results near Overschie, the question arose as to whether the 80 km/h speed limit would also lead to an improvement of air quality, noise-level, traffic flow and traffic safety at these bottlenecks. To answer this question, a detailed study was conducted to determine the effects of an 80 km/h speed limit with route control on air quality, noise-level, traffic safety and traffic flow. The effect of the speed reduction was determined for three years: the current situation (2002) and two future years (2010 and 2015). The year 2010 is relevant for the Air Quality Order and 2015 is important because of the introduction of Euro IV and V. To determine the effects for air quality, noise-level and traffic flow, we used highly detailed 'state of the art' models. The results showed that an improvement of air quality near freeways of up to 5% is possible by decreasing speed from 100 to 80 km/h (for two locations the speed decreases from 120 to 80 km/h). However, the effect varies by location. The maximum effects were found around the large cities Amsterdam, Rotterdam and Utrecht. The average improvement for NO2 was about 5%. The effect of the measure on emissions was much larger than on concentrations. The effects for PM10 concentrations were generally small, mainly because of the smaller contribution of local traffic to total concentrations. The effect is clearly larger for NO2 than PM10. The absolute effects in 2010 and 2015 were comparable with those for 2002, although the relative effect was even larger. The introduction of a speed limit with route control had, in general, a positive effect on noise levels. The average effect varied between 0,2 dB(A) and 1,3 dB(A). In 2010 and 2015, the effect was similar to the current situation. The safety-effects near Overschie were very positive: the number of accidents and victims decreased substantially (around 60 and 90%, respectively). The positive effects were caused by lower speeds and more homogeneous traffic flows because of route control. The effects for the other locations were estimated with knowledge based on empirical studies . On average, the total number of accidents decreased by 35% and the total number of injury accidents by 47%. In 2010 and 2015, the expected effects were less because of increasing intensity and congestion. An 80 km/h speed limit led to a decrease in the average speed of traffic. The largest decreases were observed in free flow situations. For almost every location, the variation in journey time decreased. Again, the largest decreases were at free flow. Network effects were minimal. The future effects were the same for most of the locations. For the covering abstract please see ITRD E135207.
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