What is the influence of different lane widths of a cross section on speed and driving behaviour in relation to other design aspects of the road? Where can we find possible turning points and what kind of compensating measures are important to reduce the consequences for traffic safety? Two experiments were performed in the TNO driving simulator. In the first exploring experiment 15 different cross section designs were tested on their effects on driving behaviour. In the second experiment, the two ‘best’ designs from the exploring experiment were further tested for effects of smaller distances to the and driving on these narrow lanes for longer periods of time. Both experiments were performed with a group of younger en elderly subjects. Experiment 1: It was found that Time to Line Crossing (TLC) is shorter when the lane gets smaller. The shortest TLC was found on the smallest lane of 2.50 m. When looking with more detail into the different cross section designs, it turns out that the maximum speed that is driven over this smaller lane is very important. A maximum speed of 90 km/h and of 120 km/h result in an even shorter TLC. Short TLC values that can be seen as unsafe (TLCs smaller than 1 s), are found more often to the left road marking than to the right road marking. Again the results show that the smaller the lane, the higher the frequency of these short TLC values. The smallest lane (2.50 m) in combination with a speed limit of 70 km/h and a lane width of 2.75 m in combination with a speed limit of 90 km/h seem to be the options. Experiment 2: During these long driver, the most important safety measures that relate to the lateral position of the driver, stay around the same average value as measured in the short drives in experiment 1. Elderly drivers do not show any differences with younger drivers. In the condition in which subjects have no maximum speed limit to obey, subjects were found to drive much faster than 90 km/h (average 116 km/h). This higher average speed also has a negative influence on other driving behaviour measures. Especially the amount of TLCs smaller than 1 s increases (to the left lane marking this amount almost doubles from 6.5 to 12.8 in 5 minutes). But also the minimum TLC decreases significantly, both the left and the right lane marking. The choice for a lane width of 2.75 m in combination with a speed limit of 90 km/h seems to be a safe one. However, this is only the case when drivers keep to the maximum speed limit. The results show that drivers want to drive much faster when they have the opportunity, resulting in negative effects for traffic safety, as shown by the TLC to the left and right lane marking. It is concluded that a lane width of 2.75 m only stays a safe option when compensating measures are taken to assure that drivers are not going to drive faster than 90 km/h. With respect to a possible difference between younger and elderly drivers, it is concluded that the chosen cross section designs do not lead to a decreased performance of elderly drivers. (Author/publisher)
Samenvatting