In most cases, the distinct point of change from one road type to another is where two separate carriageways become a single carriageway. At this point, the divided road is often a four-lane motorway, and the undivided road a two-lane highway. It is well established that two-lane highways are less safe than divided motorways, but it is not economical to provide this level of infrastructure countrywide. Where it may appear to cause a problem in terms of safety and crash history does not necessarily suggest an upgrade to a four-lane motorway should be the solution, as this may simply be relocating the transition point further along the road corridor. This paper documents an investigation on how the aspects of this scenario are currently addressed in practice, and a subsequent case study of the transition between a four-lane divided motorway and two-lane highway. (a) For the covering entry of this conference, please see ITRD abstract no. E216058.
Abstract