The Dutch motorways are becoming more and more congested due to the increasing mobility. It is however not possible to keep expanding the road capacity. The ambition of the national road network authority is to achieve more flexibility and increased performance of the existing road network. A possible way to do this is by applying dynamic speed limits. In this way, speed limits can be adjusted to unexpected situations such as weather conditions, congestion or incidents. The use of dynamic speed limits can improve traffic flow, traffic safety and the environmental impact.
To allow one to make a statement about the broader application of dynamic speed limits a study of literature has been conducted. This reveals in which circumstances dynamic speed limits can have a positive effect on traffic flow and in which circumstances the total time spent is minimized. It showed that the control approach is most important for a positive effect on traffic flow. Using this knowledge, a new control approach has been developed in which dynamic speed limits are combined with ramp-metering. This control approach can help to solve more jams compared to a control approach with dynamic speed limits. Also, a method has been developed to select locations which are suitable for the implementation of dynamic speed limits to improve traffic flow. Because most of the approaches are focused on solving wide moving jams, the method is tested in a case study for this type of jams.
To improve the developed control approach with dynamic speed limits and ramp-metering it is recommended to take into account every on-ramp and off-ramp upstream of the wide moving jam. In this way the control schedule is more realistic and more jams can be solved. When the control approach is used in practice, it is recommended to measure the flow rates with detection loops at on-ramps. The next step is to use a simulation model and a practical test with the application of dynamic speed limits to be able to predict the effects of dynamic speed limits.
