A safety assessment planning strategy proposal within the context of sustainable Urban mobility Plans: How to account for Connected and Autonomous vehicles in safety analysis in the SUMP?

In the context of Sustainable Urban Mobility Plans (SUMP), when road safety assessments are dealt with, different future scenarios are considered weighing the positive impacts of the proposed strategies for improving the transport system and road safety, globally. However, while considering those future scenarios, until now, the chance that Connected and Autonomous Vehicles (CAVs) will be introduced in the market has never been accounted. Neglecting CAVs can provide misleading results in terms of safety assessment. In this study, a general framework about how to include CAVs in SUMP safety assessments is provided. The general framework, which relies on traffic simulations and algorithms to count conflicts, was tested on two-way two-lane rural roads within the Province of Bari (Italy), where a SUMP was recently developed but the possible introduction of AVs has not been accounted, as it is a common practice in SUMP drafting. Results provided by simulations show a dramatic crash reduction when the traffic is made only of CAVs, while more dangerous situations are highlighted in the case of mixed traffic. Therefore, some countermeasures to handle mixed traffic, such as e.g., reserved lanes for CAVs in case of new roads, must be found and provided for stakeholders and practitioners while dealing with planning strategies.