Bus Rapid Transit Technologies: Assisting Drivers Operating Buses on Road Shoulders: Volume I: Final Report

Alexander, Lee; Cheng, Pi-Ming; Donath, Max; Gorjestani, Alec; Newstrom, Bryan; Shankwitz, Craig; Trach Jr., Walter · 2005 · ROSA P / University of Minnesota. Center for Transportation Studies

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Summary

This report details the development of a driver assistive system designed to enhance the safety and efficiency of Bus Rapid Transit (BRT) vehicles operating on narrow road shoulders. The research was motivated by the Federal Transit Administration’s push for BRT systems and the specific operational challenges faced by Metro Transit in the Twin Cities, where buses utilize approximately 200 miles of bus-only shoulders. These shoulders are typically only 10 feet wide, while the buses are 9.5 feet wide, leaving a margin for error of less than half a foot. This tight clearance makes lane keeping difficult, particularly in adverse weather or low visibility, and creates significant stress for drivers who must also manage merging into traffic. The project, conducted by the University of Minnesota’s Intelligent Vehicles Laboratory, involved equipping a Metro Transit bus, designated the “Technobus,” with a comprehensive driver assistive system. The core technology relied on Differential GPS (DGPS) using a Trimble Virtual Reference Station (VRS) to provide centimeter-level positioning accuracy, overcoming urban signal masking issues. The system integrated a lateral control algorithm, a steering actuator, and multiple sensor suites. Forward obstacle detection utilized dual Eaton Vorad radars, while side collision avoidance employed a “Virtual Mirror” system based on LIDAR sensors to eliminate blind spots associated with conventional mirrors. Data was presented to the driver via a Head-Up Display (HUD) showing lane boundaries and forward targets, and a graphical Virtual Mirror display. Testing of the lateral guidance system demonstrated high precision. During trials on the University Transitway at a steady speed of 35 mph, the system maintained a mean lateral error of -2.2 inches with a standard deviation of 5.1 inches. The report notes that this level of consistency would be difficult for a skilled human driver to replicate. The DGPS infrastructure proved robust, with the VRS system providing reliable corrections across the test corridors despite some gaps in wireless modem coverage. The steering actuator was designed to assist the driver without overriding manual control, ensuring safety during complex maneuvers like merging. The significance of this work lies in its potential to make bus-only shoulder operations a viable and scalable BRT strategy nationwide. By reducing the cognitive and physical load on drivers, the technology allows buses to operate at higher speeds safely, improving transit efficiency and on-time performance. The study concludes that while the lateral guidance and forward collision avoidance systems are effective, further development is needed for side collision avoidance and merging assistance. The report emphasizes the importance of partnerships with transit agencies and manufacturers to refine these technologies for broader industry adoption.

Key finding

The automated lane-keeping system maintained a mean lateral error of negative 2.2 inches with a standard deviation of 5.1 inches at 35 mph, a precision difficult for skilled human drivers to replicate.

Methodology

field_study

Provenance

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• perceptual countermeasures