Speed Behaviour and Traffic Safety in Connector Roads Second Curves

In the Dutch freeway geometric design guidelines, there is a rule that in connector roads, the second curve should not be smaller than the first curve in a connector road, so there is no need to decelerate further inside the connector road. By this it is assumed to match the expectation of the driver. Based on speed profiles in free flow situations and accident data, this research compares speed behaviour and accident risk in second curves which do or do not adhere to this rule and compare those to single curves as a baseline. In general, it can be concluded that the first curve does set expectations for the second curve which is seen in speed behaviour the curve approach phase of the second curve. Furthermore, the ratio of first and second radius is of influence to the speed at curve start of the second curve. The speed inside the curves is not different by using different radii for the first curve and comparable to single curves. The different speed behaviour in second curves for adhering to the design rules or not is however relatively small and does not seem to have an influence on accident risks.