Before-after safety analysis of a shared space implementation

Shared spaces aim to reduce the dominance of motor vehicles by promoting pedestrian/cyclist activity and minimizing segregation between road users.Despite the intended scope to improve the safety of vulnerable road users, only few works in the literature focused on before-after safety evaluations, mainly analyzing changes in users’ trajectories and speeds, traffic volumes, and conflict counts, which, while useful, cannot univocally quantify road safety. Here, the authors propose a more advanced methodology, based on surrogate measures of safety and Extreme Value Theory, to assess road safety before and after the implementation of a shared space. The aim is to produce a crash risk estimation in different scenarios, obtaining a quantitative and comprehensive indicator, useful to practitioners for evaluating the safety of urban design solutions. A real-world case study illustrates the proposed procedure. Video data were collected on two separate days, before and after a shared space implementation, and were semi-automatically processed to extract road users’ trajectories. Analysis of traffic volumes, trajectories, speeds and yield ratios allowed to understand the spatial behavior of road users in the two scenarios. Traffic conflicts, identified with an innovative surrogate measure of safety called “time to avoided collision point” (TTAC), were then used to estimate a Lomax distribution, and therefore to model the probabilistic relationship between conflicts and crashes, eventually retrieving a crash risk estimate. Results show that the analyzed shared space was able to significantly reduce the risk of crashes, and these findings are consistent with the observed changes in users speed and spatial behavior. The analyzed case study and its limitations were useful in highlighting the methodology main features and suggesting practical prescriptions for practitioners.

• Record URL:
  • https://doi.org/10.1016/j.cstp.2023.101021
• Record URL:
  • http://www.sciencedirect.com/science/article/pii/S2213624X23000755
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/2213624X
• Supplemental Notes:
  • © 2023 World Conference on Transport Research Society. Published by Elsevier Ltd. Abstract reprinted with permission of Elsevier.
• Authors:
  • Orsini, Federico
  • Batista, Mariana
  • Friedrich, Bernhard
  • Gastaldi, Massimiliano
  • Rossi, Riccardo
• Publication Date: 2023-9

Language

• English

Media Info

• Media Type: Web
• Features: Figures; References; Tables;
• Pagination: 101021
• Serial:
  • Case Studies on Transport Policy
  • Volume: 13
  • Issue Number: 0
  • Publisher: Elsevier
  • ISSN: 2213-624X
  • Serial URL: http://www.sciencedirect.com/science/journal/2213624X

Subject/Index Terms

• TRT Terms: Pedestrian vehicle interface; Safety analysis; Urban design; Vehicle mix
• Subject Areas: Highways; Pedestrians and Bicyclists; Safety and Human Factors;

Filing Info

• Accession Number: 01893806
• Record Type: Publication
• Files: TRIS
• Created Date: Sep 21 2023 8:58AM