Safe Operations at Roadway Junctions - Design Principles from Automated Guideway Transit: SAE Technical Paper No. 2021-01-1004

J. Lott, Stanley Young, Lei Zhu

Research output: Contribution to conferencePaper

1 Scopus Citations


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
Number of pages10
StatePublished - 2021
EventBusiness of Automated Mobility (BAM) Forum -
Duration: 23 Jun 202124 Jun 2021


ConferenceBusiness of Automated Mobility (BAM) Forum

NREL Publication Number

  • NREL/CP-5400-78894


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


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