A driving simulation study on the effects of situational and route familiarity for different unsignalized mid-block pedestrian crossing layouts

The 2021 edition of the Italian Highway Code includes for the very first time the vulnerable road user (VRU) category. This innovation reflects the growing awareness of the Italian legislator for the safety of pedestrians, two-wheelers, and persons with disabilities. The coexistence of all road user categories is the specificity of urban mobility. In this context, a significant amount of vehicle-pedestrian collisions occurs at unsignalized crosswalks located between consecutive intersections, i.e. in the so-called “mid-block” section. This study investigates the effects of two different crosswalk designs, (i) the linear sidewalk and (ii) the curb extension, on driver pedestrian (DP) interaction. Two types of driver familiarity were explored: (i) the route and (ii) the situational one. The hypothesis is that drivers’ familiarity with route and situation contributes to generating a wider spectrum of behaviours, which in turn can significantly affect pedestrian safety. Although the route familiarity has been repeatedly investigated in the literature through naturalistic and simulation studies, there is a lack of knowledge about the effects of familiarity in the DP interaction. The experiment aims to examine the driver behaviour after (i) repeated exposure to DP interactions and (ii) in the first exposure after several missed DP interactions at mid-block crosswalks. This study was conducted at the fixed-base driving simulator of the Department of Environment, Land and Infrastructure Engineering at the Politecnico di Torino. A multi-level factorial experiment was designed to include: (i) mid-block crosswalk design, (ii) driver familiarity, and (iii) pedestrian time gap acceptance. Baseline (linear sidewalk) and curb extension are the two designed mid-block pedestrian crossing layouts and are embedded in an urban neighbourhood. Unfamiliarity, route-familiarity, and situational-familiarity are the three conditions in which the participants (drivers) were involved. Three different values of pedestrian time gap acceptance to model their crossing behaviour (4, 6 and 8 seconds) were adopted. Fifty-two participants were involved. They were divided into four groups and stratified for age and gender. Four surrogate safety measures i.e., minimum instantaneous time to collision (MTTC), post encroachment time (PET), maximum car deceleration (MaxD) and maximum car speed within 100 m before the crosswalk (MaxS) were used to evaluate the driver response. Two different analysis were carried out. The first with interaction plots exhibited the effects of the experimental factors on the measured variables. The second was performed through the calibration of mixed-effects models. Results reveal that the curb extension layout significantly improves the safety of the pedestrians, showing the more relevant effect on MTTC and MaxS. Furthermore, the analysis pointed out that route familiarity led to more aggressive driving behaviour than the other familiarity levels. Situational familiarity positively affects driving behaviour making them more prone to safely interact with pedestrians. The outcomes suggest adopting the curb extension at the unsignalized mid-block pedestrian crossing, and this conclusion is also supported by a lower number of collisions recorded during the simulations with this layout.