Reduced sight distance on existing rural roads : how can we defend it?

This paper presents the results of research by the Queensland Department of Main Roads into sight distance issues relating to existing roads. The Department formalised the use of reduced sight distance for crests on existing roads in 1981. This used a 'reduced manoeuvre sight distance model'. However, no explanation of the key manoeuvre time parameter was given. Nor was the operation of large commercial vehicles explicitly covered. Given the increasing need to be able to defend road geometry, this paper proposes how reduced sight distance may be defended in terms of the intent of the sight distance standards for a new road. An extreme case of the reduced manoeuvre sight distance model is used as an example for assessing how much of the intent of the manoeuvre sight distance standard is achieved. This paper also applies the findings in another paper by the author that investigated the latitude that is available in the standard stopping sight distance and manoeuvre sight distance models that are used in road design. (Author/publisher) For the covering entry of this conference, please see ITRD abstract no. E208431.