Running off the roadway to the right (accident type 8) is the most common accident type for accidents involving personal injury and serious personal injury on rural roads. Since numerous international studies for motorways as well as a few for rural roads have shown that a considerable proportion of run-off-road accidents to the right can be avoided by means of rumble strips milled into the hard shoulder next to the lane, the aim of this study was to identify a suitable form of rumble strip for rural roads and to implement this on selected pilot routes in order to subsequently investigate its safety effect. Since international experiences also report a positive safety effect of rumble strips milled into the central reservation, this measure was also to be examined in a pilot application. In the first part of the study, the international experiences were first evaluated within the framework of a literature analysis. With regard to the shape of the rumble strips, it quickly became clear that sinusoidal or elliptical rumble strips are preferable to the classic rectangular rumble strips on rural roads, as these generate a low external noise and their passability is less critical for single-track vehicles (bicycles, motorcycles). Based on the findings from the literature, empirical investigations (vibration and noise measurements with two-track vehicles as well as driving tests with single-track vehicles) were carried out on a closed-off test track for twelve different rumble strip variants in the next step. The twelve rumble strip variants differed with regard to both the basic shape and the dimensions. A completely new form of rumble strip (combination of elliptical and sinusoidal shape) was identified as the preferred variant. In the next step, this shape was milled into the hard shoulder on two suitable pilot sections (4.15 kilometer long section of the B 55 near Warstein in North Rhine Westphalia and 2.8 kilometer long section of the B 313 near Trochtelfingen in Baden-Wuerttemberg). In addition, on a 2.75 kilometer long 2+1 section of the B 33 near Triberg in BW, the rumble strip was milled into the central reservation. On all three pilot sections the rumble strips were milled in 2010. On the basis of a three-year follow-up period after milling the rumble strips, the safety effect can be summarized as follows: The rumble strips milled into the hard shoulder proved to be an effective measure for reducing the number of run-off-road accidents to the right (accident type 8). The positive international experiences could thus be confirmed, albeit only on the basis of an extremely low data basis. For the 2+1 section of the B 33, on which the rumble strips were milled in the central reservation, it can be seen that the effect of the measure in relation to collisions with oncoming traffic (accident type 4) and run-off-road accidents to the left (accident type 9) is partly negative. Contrary to international experience, therefore, the pilot study carried out did not reveal any positive impact of this measure. The effectiveness of rumble strips milled into the roadside and the central reservation determined within the framework of the pilot study on rural roads could not represent a generally valid result due to the small sample size on which the investigations were based. In the case of the rumble strips milled into the hard shoulder, however, the pilot studies could confirm the positive international experience for this infrastructural measure, so that their use at existing specific problem areas under the boundary conditions defined within the framework of this project should be considered as a possible measure for improving traffic safety. However, the widespread use of rumble strips milled into the hard shoulder on rural roads does not appear to be appropriate against the background of the progressive spread of lane departure warning systems. With regard to the effectiveness of rumble strips milled into the central reservation, the positive international experience could not be confirmed by means of the examined pilot section. However, further investigations should be carried out before this measure is definitely rejected. Finally, the durability of the rectangular rumble strip milled on a 36 kilometer long section of the A 24 motorway at Herzsprung in 2003 was evaluated. As a result of the laser profile measurement, no edge breaks could be detected both lengthwise and crosswise to the direction of travel. (Author/publisher)
Abstract