Mathematical models to determine the influence of road parameters and conditions on vehicular speed

The study of vehicular movement modes in adverse weather conditions allowed defining the dependence of traffic modes at certain road segments on weather conditions. It is found that the average vehicle speed changes within a year over a wide range depending on road conditions even on its straight horizontal sections. There is a considerable difference in the maximum speed of traffic movement. Complex road sections significantly influence the traffic mode during any period of the year, especially in adverse weather conditions. The road surface condition exerts the greatest impact on the traffic speed. If the adhesion coefficient equals 0.2-0.3 the average traffic speed is 20-25% lower than if that adhesion coefficient equals 0.5-0.6, and in ice conditions the average traffic speed decreases by 40-50%. The proposed calculation formula allows defining the influence of weather conditions on the traffic mode of free-moving cars or cars in a joint traffic flow. It provides for the feasibility study regarding measures aimed to increase the traffic speed in adverse weather conditions of the year. Based on the observations and calculations the correlation dependences of average and maximum traffic speeds on the adhesion coefficient within a 7.0 m-wide road without the hard shoulder were obtained.