Comparison of International Methods to Estimate Maximum Speed Through Roundabouts

Roundabout operating speed estimation is a critical aspect of safe roundabout infrastructure design, yet existing international guidelines for speed evaluation exhibit inconsistencies and limited agreement with actual observed speeds at roundabouts. This study provides a comprehensive evaluation of five existing international guidelines and their implications for roundabout safety. This study focused on the discrepancies between estimated and observed fastest path speeds by conducting Passing–Bablok regression analyses of speed estimates evaluated from guidelines from Australia, the Netherlands, the United Kingdom, the USA, and South Africa, and speeds observed at 29 roundabouts, encompassing both single- and double-lane configurations. This study represents the most extensive comparison between methods used in various countries for fastest path analysis and is the first instance of empirical fastest path speed assessment. A widening of the confidence intervals around regression lines at higher speeds indicated poor agreement between estimated and observed speeds. All minimum observed speeds exceeded estimated design speeds for double-lane roundabouts signaling a failure of current design methodologies to sufficiently reduce speeds. The findings of the study uncover a systematic tendency for international guidelines to underestimate operating speeds lower than 60?km/h and overestimate higher speeds, posing significant safety concerns. This discrepancy not only challenges prevailing assumptions about roundabout safety but also highlights the potential for a false sense of security among designers. By shedding light on these discrepancies, insights are gained to inform more accurate speed estimation methods, thereby contributing to improved design practices and sufficient speed reduction at roundabouts.

• Record URL:
  • https://doi.org/10.1177/03611981241308871
• Availability:
  • Find a library where document is available. Order URL: http://worldcat.org/issn/03611981
• Supplemental Notes:
  • Jared Tyrell Arries https://orcid.org/0009-0009-9463-9641© The Author(s) 2025.
• Authors:
  • Arries, Jared Tyrell
  • 0009-0009-9463-9641
  • Bruwer, Megan Melissa
  • 0000-0002-0337-9314
  • Krogscheepers, Johann Christoff
• Publication Date: 2025-5

Language

• English

Media Info

• Media Type: Web
• Features: Figures; References; Tables;
• Pagination: pp 273-290
• Serial:
  • Transportation Research Record: Journal of the Transportation Research Board
  • Volume: 2679
  • Issue Number: 5
  • Publisher: Sage Publications, Incorporated
  • ISSN: 0361-1981
  • EISSN: 2169-4052
  • Serial URL: http://journals.sagepub.com/home/trr

Subject/Index Terms

• TRT Terms: Design speed; Geometric design; Highway safety; Predictive models; Roundabouts; Speeding
• Geographic Terms: Australia; Netherlands; South Africa; United Kingdom; United States
• Subject Areas: Data and Information Technology; Design; Highways; Safety and Human Factors;

Filing Info

• Accession Number: 01944156
• Record Type: Publication
• Files: TRIS, TRB
• Created Date: Jan 28 2025 9:19AM