COST-EFFECTIVE AND USER-ORIENTED SIZING OF RURAL ROADS

Analyzed in this paper are two important aspects of road sizing: the common approach to selecting the 30th highest hourly volume for design hourly volume (DHV) for all types of road uses; and the development of a cost-effective annual average daily traffic (AADT) criterion for upgrading two-lane rural highways. The study's most important feature is that the road type variable is used in a more detailed and objective manner than in past studies. The highway system for Alberta, Ontario, Canada is investigated and roads are classified into six types according to trip characteristics (e.g., trip purpose and trip length distribution). Based on other road design and traffic data, and economic cost statistics from Alberta Transportation, a detailed economic analysis is carried out. The main conclusions of this study are that: (a) the type of road use is a significant variable that must be considered for appropriate sizing of roads from the economist's and user's perspectives; (b) to provide a more uniform service to the users of various road facilities, it is more appropriate to use a range of highest volume hours for the design of different types of roads; (c) the total highway cost is minimized typically at a volume-to-capacity ratio of 0.35 regardless of the type of road use; and (d) the typical AADT values at which two-lane rural roads would need upgrading vary from a range of 1,750 to 2,500 for highly recreational routes to 6,500 to 8,500 for commuter routes.