VARIABLES INFLUENCING SPEED DISTRIBUTION ON URBAN ARTERIALS AND COLLECTORS

Speeds are affected by several variables such as driver characteristics, vehicle performance, road geometrics, environmental conditions and driving regulations. A knowledge of the relationship between speed and such variables allows conscious speed management on existing and planned roads, with the aim of constraining drivers to select a speed consistent with the posted speed limit. This relationship is of great interest to those who wish to achieve roadway functionality and improve overall safety. Focusing on this objective, some contributions concerning urban roads are already available in literature with the caveat that they can be applied only to specific road types and recently built-up areas. Moreover, they refer mainly to the 85th percentile of speed. Lastly, they can only be applied in locations which are homogeneous in terms of environment, driving regulations and vehicle type. The research aims to establish the correlation of roadway features to operating speed by elaborating panel-data models for the urban environment. The paper presents the results of an investigation carried out on Italian urban arterials and collectors within the municipality of Torino (Italy). The fact that this area is characterized by dissimilar geometric features facilitated the inclusion and study of a fully representative range of variables. Models were calibrated by combining the complete dataset and disaggregating it for the different road typologies. The results showed that, when consideration was given to all the selected variables, some variables were found to be ever present and statistically significant for all models.