QUALITY OF FLOW AND TRAFFIC SAFETY ON GERMAN EXTRA-WIDE HIGHWAYS

In recent years, the advantages and disadvantages of the so-calle extra-wide highways have been studied. These are considered as a road category with extra-wide lanes (ie 5-6.5 m lane width) betwe two-way highways andmotorways so that overtaking is continuously possible. The advantage of these extra-wide highways is seen in better driving comfort especially with respect to choice of speed Comprehensive measurements of traffic flow situations and an anal of safety aspects were undertaken on five road sections using induction loops and video observations for data collection. For t purpose a new configuration for the location of induction loopswa developed to be able to detect overtaking within the extra-wide lanes. More than 500 traffic accidents on these facilities were analysed. Thestudy was designed to quantify traffic flow and saf criteria in comparison to those on normal two-way highways and motorways. The study showed that extra- wide highways can serve a alternative to normal two-way highways, because the widening to extra-wide lanes increases the quality of flow and decreases at t same time the accident risk. This road type can therefore be recommended when traffic demand does not require a motorway and w cost and environmental effects are crucial. (a)