Free speed distributions — Based on empirical data in different traffic conditions

Free speeds are defined as the speeds pedestrians like to walk with when they are not hindered by other pedestrians. Since pedestrians have different characteristics influencing their choices, free speeds will differ among individuals. These pedestrian characteristics are often not taken into account explicitly, which makes it necessary to describe free speeds as a stochastic variable with a distribution. Moreover, (free) speeds will be influenced by the characteristics of the walking infrastructure, such as grade, length, width, the type of pedestrian facility, and weather and other external conditions. Free speeds and their distribution play an important role in many traffic flow models, but are also relevant in other applications. The aim of this research is to derive free speed distributions for a number of traffic flow conditions. The data on which the distributions are estimated come from large-scale laboratory walking experiments. In these experiments different traffic conditions are simulated, such as unidirectional flows, opposite flows, and crossing flows. Free speeds are highest in unidirectional flows (1.54 m/s), somewhat lower for opposite flows (1.41 m/s), and lowest for crossing flows (1.35 m/s). Reduction of this free speed is due to the interaction with other flows. For opposite flows, this interaction is reduced by lane formation (effect of self-organisation). For crossing flows however, this interaction cannot be reduced, since the flows have to interact during the crossing.