The density of traffic within urban areas depends on multiple factors, and among those; one
that has major impact is the weather. This paper presents a study that empirically analyzes
the traffic flow velocity depending on the atmospherically conditions and the day schedule.
The objective is to assess systematically to which extent there is a correlation between the
vehicle velocity on an urban environment and the weather, depending on the time of day.
The presented case of study uses a set of real data, specifically the trips made by taxis in the
city of Porto (Portugal). First, the vehicle GPS routes are analyzed to identify departure and
arrival points and estimate the route average velocity and adding weather and time
conditions. The data is processed with different regressive techniques to obtain the influence
of the variables on the velocity. The results show differences between days of the day and
weekends, as well as differences in speeds with a favorable climate for driving compared to
other more adverse ones.
