Influence of Weather on Traffic Flow: An Extensive Stochastic Multi-effect Capacity and Demand Analysis

Traffic is affected by a wide range of variables. An influential and commonly occurring variable on traffic flow is the weather. Weather conditions affect both traffic demand as well as road capacity and in doing so also affect the traffic fluency, or rather the ability of traffic to maintain a certain level-of-service. In this contribution it is argued that the influence of weather should be considered holistically for simultaneous influence on both the demand and supply. Furthermore, a case is made to quantify such outcomes stochastically, as traffic is rarely in an average state, especially when considering such stochastic variables as the weather. This is backed up by an extensive data analysis into the effects of rain, snow, temperature and wind on road capacity, traffic demand and traffic fluency. This found the effects on the traffic fluency of rain to be limited due to a reduction in both capacity and demand on relevant days. The effect of cold temperatures was especially shown to affect traffic to a greater extent. Results from snowfall remained inconclusive due to limited observations.