Safe Operations at Roadway Junctions - Design Principles from Automated Guideway Transit

J. Lott, Stanley Young, Lei Zhu

Research output: Contribution to journalArticlepeer-review


This paper describes a system-level view of a fully automated transit system comprising a fleet of automated vehicles (AVs) in driverless operation, each with an SAE level 4 Automated Driving System, along with its related safety infrastructure and other system equipment. This AV system-level control is compared to the automatic train control system used in automated guideway transit technology, particularly that of communications-based train control (CBTC). Drawing from the safety principles, analysis methods, and risk assessments of CBTC systems, comparable functional subsystem definitions are proposed for AV fleets in driverless operation. With the prospect of multiple AV fleets operating within a single automated mobility district, the criticality of protecting roadway junctions requires an approach like that of automated fixed-guideway transit systems, in which a guideway switch zone "interlocking"at each junction location deconflicts railway traffic, affirming safe passage. The analogous AV protection safety subsystem is defined as fail-safe equipment that monitors roadway intersections and junctions, communicates traffic signal status, perceives and communicates alerts and signals to AV connected vehicles concerning potential unsafe conditions, and performs related primary safety functions. Conclusions are drawn that the AV protection roadway intersection functions must be performed by local roadside equipment dedicated to protecting each roadway intersection and junction. Further, it is concluded that the communications technology connecting the infrastructure with the vehicle to perform this vital, fail-safe protection should meet specific functional and performance criteria.

Original languageAmerican English
Pages (from-to)260-269
Number of pages10
JournalSAE International Journal of Advances and Current Practices in Mobility
Issue number1
StatePublished - 2021
EventSAE 2021 Business of Automated Mobility Forum, BAMF 2021 - Virtual, Online, United States
Duration: 23 Jun 2021 → …

Bibliographical note

Publisher Copyright:
© 2021 Institute of Physics Publishing. All rights reserved.

NREL Publication Number

  • NREL/JA-5400-80888


  • analysis methodologies
  • automated vehicles
  • autonomous vehicles
  • communication systems
  • control systems
  • fleets
  • public transportation systems
  • risk assessments
  • traffic management


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