THE CONNECTION BETWEEN LANE-CHANGING BEHAVIOUR AND LANE DISTRIBUTION ON TWO-LANE MOTORWAY CARRIAGEWAYS

In areas having high traffic flows on two lane motorway carriageways, the proportion of traffic using the right-hand lane is 1/3 and that using the overtaking lane is 2/3 of the total. The cause of this unequal loading has been found in the lane changing situation. It shows that in the overtaking lane very much smaller headways are accepted than in the nearside lane. The survey was carried out on the motorway-survey area between Bruchsal and Karlsruhe, unnoticed by vehicle drivers. The results are based upon data provided by the macroscopic evidence of 2000 lane changes. With increasing traffic flow the proportion using the nearside lane reduces. A balanced flow may be expected at about 1200 vph. With increasing traffic flow the frequency of lane changing reaches a maximum of 600 changes per hour. Alternatives to the changing of lane distribution were investigated. Only a reduction of the opportunity function for lane changing to the left is appropriate to improve lane distribution, without increasing the frequency of change. An increase in efficiency with an equal distribution on both lanes is likely to be achieved only in occasional circumstances. (TRRL)