Assessment of operating speeds of rehabilitated rural roads with asphalt surfacing

Abstract

In Sri Lanka, rural roads are not explicitly designed on technical requirements. So far restoration of rural roads went through with mere Construction enhancements and appropriate geometric improvements have not been adopted. Itwas discovered that the actual operating speeds can be higher after restoration which is affecting the safety of road users. Aim of this research is to survey operating speeds, posted speed limits and to find design operating speeds that expected to be after the rehabilitation. The majority of the rural roads in Sri Lanka does not have posted speed limits indicated by the geometric, road environment and functionality level of the road. Consequently, the speed decision of the rural road drivers relies upon variety of different factors. The 85th percentile speed was taken as the operating speed. This speed was utilized as a basic for recommending rational speed limit. Selected roads were divided into a few segments; straight and curved. Operating speed on straight segments were given priority in suggesting rational speed limits. As operating speed in curves are considerably lower and enforcing lower posted speeds only based on operating speeds on curves for entire road and would not be practical. The recommended speed limit for all the roads under purview is 50 km/h and this speed limit will be superseded to a lesser speed limit at a curved segment, dependent on the operating and design speed. This speed limit should be notified using sign boards and shall be enforced only for the curve itself.