Within the framework of BKA phase 2 (Basiskwaliteit Autosnelwegen) a couple of driving simulator experiments have been performed. These experiments studied the relation between different design elements of a cross section and driving behaviour. The results from the explorative part (see Hoedemaeker et al., 2002) show that a cross section design with a maximum driving speed of 70 km/h in combination with a left lane width of 2.50 m is a realistic option. Therefore a supplementary experiment has been performed that can be seen as an extra condition of the original experiments. The research question of the current experiment are: 1 Does cross section design 1 (70 km/h, 2.50 m) stay a safe choice when drivers drive this narrow lane for a longer period of time? 2 Is there a difference between younger and older drivers? 3 Which speed do drivers chose when they have no restrictions? 4 Which lane do drivers chose when they have the freedom to chose? Subjects drove the TNO driving simulator on cross section design 1 (70 km/h and 2.50 m width), in combination with a distance to the crash barrier of 1.25 m and of 0.50 m. In supplementary conditions the subjects were able to chose their own speed and lane. In the course of the 40-minute drive no effects were found that show a decrease in driving performance. The most important safety measures that concern the lateral position of the driver stay around the same average value as when driving for a shorter period of time. Even in comparison with the 2.75 m/90 km/h cross section design, the minimum time to line crossing (TLC) turns out to be larger on a left lane of 2.50 m and a speed limit of 70 km/h. Logically, the amount of TLCs smaller than 1 s is also smaller in this design. This effect can be explained by the lower speed that is driven on this narrow lane. So, especially this lower speed limit of 70 km/h makes a narrow lane of 2.50 m to be still a safe option. The time of the line crossings, however, does not differ between the 2.50 m and the 2.75 m designs. To the left as well as to the right lane marking the time of the lane crossings is between 0 and 2.5 s, which is not alarmingly much. However, it turns out that when subjects are free to chose their own speed, the average driving speed increased from 70 km/h to 109 km/h. This increase also affects a couple of other driving measures in a detrimental way. The minimum TLC decreases and the number of TLCs under 1 s increases alarmingly (to the left lane marking even from almost 5 to almost 18 in 5 minutes). Traffic safety on a left lane width of 2.50 m or 2.75 m is heavily dependent on the actual speed that is driven. A cross section design of 2.50 m in combination with a speed limit of 70 km/h is still a safe choice when drivers drive this lane for longer periods of time. There are no differences between younger and older drivers. An important factor is the presence of a profile right lane marking. When drivers do not have any restrictions with respect to their speed, they will drive much faster which makes this cross section design an unsafe choice. Strict maintenance of the 70 km/h speed limit is a requirement. (Author/publisher)
Abstract