Speed Management in Rural Two-way Roads: Speed Limit Definition through Expert-based System

Until recently, the design of road infrastructure involved mainly concerns related to the base speed value and to high levels of service. However, it is today consensually accepted that only an integrated approach is able to take into account the interests and needs of all the involved users. This vision led to different approaches on speed management along the road. During the last decade, new speed limits setting methodological approaches have emerged, based on new design models and tools, which take into account road geometric, safety and operational characteristics. This research work aimed to develop a decision-support methodology for the definition of the appropriate maximum speed in each road section, with a widespread use, applied to single carriageway roads in interurban areas, crossing different road environments with a mixed use. An analytical model able to accurately estimate that speed limit was developed based on a set of objective and easily measurable and obtainable explanatory variables characterizing the section under analysis and its surrounding areas. The resulting methodology is a Multinomial Logit model, and it was carried out using a case-study involving four different tracks of interurban roads crossing different environments. The model was estimated resorting to the use of values chosen by four traffic safety experts recorded for each road segment in both directions.