Driver Assistive Systems for Transit Buses -- University of Minnesota Going Strong with $700K in Grant Funding
IVsource.net
14 March 2002

Researchers at the Intelligent vehicles lab at the University of Minnesota have successfully garnered at least $700K in research funding from USDOT to study and implement driver assistive technologies for bus drivers. Work includes requirements analysis and prototype system development and evaluation in a real-world environment.

Researchers at the Intelligent vehicles lab at the University of Minnesota have successfully garnered at least $700K in research funding from USDOT to study and implement driver assistive technologies for bus drivers. A $300K grant from the Research and Special Programs Administration (RSPA) comes their way as part of their University Transportation Centers research program, and the remaining $400K was competitively awarded by the Federal Transit Administration (FTA) late in 2001 as part of the FTA Intelligent Vehicle Initiative (IVI) program.

The FTA project focuses more on requirements analysis and the RSPA project involves prototype system development and evaluation in a real-world environment. Thanks to information provided by the University of Minnesota website and Brian Cronin, Transit IVI Program Manager at FTA, a useful picture of these unique projects emerges.

Systems Requirements Analysis -- Bus Rapid Transit and Intelligent Vehicle Initiative

During Intelligent Vehicle Initiative (IVI) and Bus Rapid Transit (BRT) industry meetings, the transit industry has continued to support the need to enhance transit operations and efficiency through the deployment of safe technology assistance systems. With the increased planning and deployment of BRT Systems, the transit industry continues to look for dedicated right-of-way, freeway shoulders, and other express lane options to increase throughput of vehicles. Transit authorities are planning to install technology assistance systems to help vehicles operate in high-speed lanes and potential high-speed stations. Since operations in these environments could pose a safety threat, it is necessary to properly assess the system design issues related to assisting vehicle operations for Bus Rapid Transit.

One of the more likely candidate IVI applications to be initially implemented on BRT systems will be lane assist technology. The premise behind lane assist technology is to increase the safety of BRT vehicles as they operate in the more unique environments, such as narrow lanes. Lane assist technology can significantly help BRT vehicles operating in the following environments:

• Narrow Lanes-Where road width restrictions are severely limited and lateral movement tolerances are low, thus limiting maximum speed and increasing the risk of hitting pedestrians, barrier or vehicles.
• High Occupancy Vehicle (HOV) Lanes-In situations where there is no positive separation of HOV lanes from non-HOV lanes, speed differentials may limit the maximum speed of buses due to their size and concerns about colliding with other vehicles. In positive barrier HOV lanes, the narrowed lanes may limit maximum speeds due to significantly decreased lateral movement tolerances.
• Bus Shoulder Lanes-The use of shoulder lanes for buses is usually a sign of severe congestion on the roadway facility. Bus shoulder lanes are usually some type of improved lane where buses may operate either at certain times or only when there is congestion. This presents a safety issue of increased speed differentials and the increased probability of BRT vehicles colliding with violators who use the bus shoulder lane to bypass the congestion.

In addition to maintaining safety, lane assist technology will also allow BRT vehicles operating on dedicated lanes in their dedicated right-of-way the ability to provide a rail-like image, which is a highly desirable feature of most BRT systems.

Lane Assist System Requirements

In the project, system requirements are being established which examine potential operating environment situations and the business case. Based on the required functions, the project team is setting requirements for the design of the vehicle and infrastructure IVI systems. In order to come to some recommendations, the project team may evaluate in-pavement and/or sensor based systems that will provide vehicle assistance. A lane assist system is expected to integrate the sensor system, steering controller, steering actuator, driver interface, roadside-to-vehicle communication system, and system diagnostics.

Initial research is building upon and expanding current research and development that is already occurring with lane assist systems on other IVI platforms, and with transit IVI collision warning systems. Initial work includes the following:

A. Identify Research and Development Partners

• Establish a management review committee from the BRT Consortium (a national group of US transit agencies interested in implementing BRT) that will provide input as to expected operating characteristics of a lane assist system within their BRT area, and will provide guidance and review of the research.
• Identify team members necessary to conduct fundamental research and testing.

B. Assess the need for Lane Assist in current BRT systems

• Research and document current lane assist and lane keeping technologies.
• Define current BRT system operating environments
• Assess whether current technology meets BRT need.

C. Fundamental Research and Testing

This task will be the fundamental aspect of the project and will include research and evaluation to document the advantages and need for lane assist systems as a solution. Research should include the following:
Identify human factors issues of drivers and passengers on BRT system with lane assist technology installed.
Identify driver effects when lanes narrow from 12' to 10' to 8' while still maintaining normal operating speed. Examine driver's ability to navigate course, tiredness, comfort level etc.
Evaluate driver recovery techniques and ability to recover/react to a warning or assistance activity as presented by a system
Define most appropriate technology for operating environment (i.e., snow, rain, heat, fog, sun, ice, etc.)

D. Assess Lane Assist Technology for Use/Transition to Precision Docking

Lane assist technology may be used for precision docking, or may need some enhancements to provide precision docking capability. This task will:

• Identify precision docking requirements
• Compare requirements to lane assist requirements
• Provide recommendations for necessary research as needed to match the needs

E. System Requirements Report

The final report will identify the system requirements, results of the research and testing, and make recommendations for next steps, which may include prototype design, evaluation, and implementation.

Prototyping Driver Assistive Systems for Minnesota Buses

Objectives
Within the RSPA project, the primary objective is to equip a Metro Transit bus with driver assistive technology that will enable bus drivers to better guide a wide bus on a narrow shoulder, especially under difficult conditions. This driver assistive technology is being adapted from the University's previous work on driver assisted snowplows, and optimized for the bus driver. The technology associated with the primary objective will be aimed primarily at assisting drivers with lane keeping and forward collision avoidance tasks.

The secondary objective is to investigate the virtual mirror and the virtual bumper as techniques for side and rear collision avoidance for transit applications. The virtual mirror has been implemented using existing geospatial database tools and DGPS as a range sensing device; however, for practical applications, radar or similar ranging sensors will have to be used. Requirements for side and rear looking radar will be developed and justified using simulation and analytical techniques.

The third objective will be to develop long term relationships with Metro Transit, the Federal Transit Administration (FTA), and technology providers to develop and implement strategies to improve transit operations. For instance, improving the ability of a bus driver to merge into and out of traffic is a high priority. Improved bus guidance technology will make bus-only shoulders a viable alternative throughout the country.

Twin Cities BRT

Metro Transit and Mn/DOT at the present time are cooperatively operating a BRT-like capability throughout the Twin Cities metro area. Buses operate in HOV lanes and on specially designated Bus-Only road shoulders; albeit at speeds significantly lower than limits posted for the adjacent highway. At the present time, Metro Transit has 118 shoulder miles approved for BRT with metered ramp by-pass capabilities in certain locations. Approximately 15 to 20 miles of approved shoulder miles are added annually. These shoulders are considered by the FTA to be Lateral Guideways and thereby qualify for federal funding. In many parts of the country, bus-only shoulders represent the only way to provide the travelling public with a fast alternative to sitting on congested roads along with everyone else in their cars. By enhancing bus-only shoulders, they become a more viable component to be integrated in future BRT systems. Bus Rapid Transit systems are of high interest because they are likely to provide the transit passenger with faster, more comfortable and more efficient service when compared to traditional transit methods and are more cost effective than Light Rail Transit (LRT).

Although the bus only shoulder policy continues to be a very successful program, it does have its challenges if you're behind the wheel. Emerging driver assistive technology developed at the University of Minnesota is aimed at solving problems associated with driving on these bus-only shoulders. For instance, most of the shoulders on which transit buses operate are no more than 10 feet wide; a transit bus measures 9 feet across the rear view mirrors. These narrow lanes require that a driver maintain a lateral error of less than one-half foot to avoid collisions. This is a difficult task under the best conditions, and degrades to near-impossible during conditions of bad weather, low visibility, high traffic congestion, etc.

In addition to maintaining the desired lane position, a driver also has to merge into traffic when the bus only shoulder area ends or when a left exit is required. Although theoretically the bus has the right of way in such a situation, many times the driver has to "fight" for his or her position. This also adds considerable stress to an already difficult task.

The University's current work is the first phase of a multi-year plan to adapt and develop driver assistive technology optimized for bus operations. The work is focusing focus primarily on lane keeping and forward collision avoidance driver assistive technologies originally developed for snowplows. The secondary (and long term) focus is on collision avoidance for the rear and sides of transit vehicles.

Task Descriptions

Task 1: Problem Refinement

This will include meeting with drivers of all experience levels to determine details regarding the difficulties of driving a wide bus on a narrow shoulder, to include "ride-alongs" to get a better idea of the problems facing bus drivers. Concurrently, select Metro drivers will be provided a demonstration of the current state of the art in driver assistive technologies as developed by the Intelligent Vehicles (IV) Lab. Focus groups will then be held to determine a point from which initial work can begin.

Task 2: Optimal DGPS Correction Broadcast Design

One of the issues delaying the widespread deployment of DGPS is the lack of available methods upon which GPS corrections can be broadcast. These issues are very complicated in metropolitan areas where population density is high and RF bandwidth is highly utilized. To provide timely GPS corrections to the buses equipped with these driver assistive packages, a number of possible correction delivery methods will be researched.

Task 3: Infrastructure Build

In this task, the infrastructure necessary to provide lateral lane keeping will be built and installed. The infrastructure includes the procurement and installation of the GPS receiver used as a base station, the procurement and installation of the chosen method of providing GPS corrections, and the creation of the geospatial database needed for lane keeping and forward collision avoidance.

Task 4: Bus Mechanics and Dynamics

The research team has considerable experience with heavy and specialty vehicles (i.e., semi tractor-trailers, snowplows, etc.), but limited experience with large transit vehicles. Metro Transit buses are rear engine, sometimes articulated, which leads to significantly different steering systems and mass distributions different than those on other research vehicles. For this task, Metro Transit will identify a bus which will be used for the work proposed herein. University researchers will study mechanical components (primarily the steering gear) so that steering actuation can be provided and study the cabin layout (for mounting of the driver assistive displays and requisite computer and sensor hardware). Moreover, University researchers will investigate bus lateral and longitudinal dynamic capabilities (necessary because of the rear engine configuration and the change of handling properties between the loaded and unloaded conditions) both on a skid pad (if available) and during normal vehicle operation.

Task 5: Driver Assistive System for Vehicle Guidance.

In this task, university researchers will install the mechanical, electronic, sensor, actuator, and display systems necessary to provide lateral driver assistance to a bus driver operating a wide bus on a narrow shoulder. This technology will be adapted from the system presently under development for the SAFEPLOW program and optimized for transit buses.

The technology to be included in the longitudinal driver assistive system includes a heads-up display (HUD), a DGPS system, an Inertial Measurement Unit (IMU), forward looking radar, power supplies, computers, steering actuation and amplification, and other peripheral equipment required to provide lane keeping driver assistance. Researchers and Metro Transit will cooperate to determine suitable locations where development can be performed.

The HUD will be used to provide the driver assistance when visibility conditions are poor and it is difficult to identify both lane boundaries and obstacles. Modifications will be made to the standard HUD model as needed to provide a driver with additional information if required. An active steering wheel will provide haptic feedback to provide additional cues to the driver. Under general operating conditions, the active steering wheel may act as the primary driver interface.

Task 6: Collision Avoidance for Transit Applications

Task 6 represents the higher risk component of the proposed research. To appreciate this, it is necessary to revisit Task 5. Task 5 represents an adaptation and optimization of technology previously developed for snowplows. Task 5 includes longitudinal collision avoidance under low visibility conditions in the sense that a forward looking radar is used to detect objects in the forward path of the bus, and the HUD is used to provide an iconic representation from which the driver can estimate the range, range rate, and azimuth angle to radar detected obstacles. However, avoiding collisions around the periphery of the vehicle has not yet been investigated. This latter objective is the primary focus of Task 6. Two particular components of this collision avoidance problem will be considered; sensing and the driver interface.

For sensing, both radar and a scanning laser rangefinder are being investigated. For the driver interface, a technology presently under development at the University may provide an effective and intuitive approach. This technology, known as a "virtual mirror," integrates geospatial data (using the same database as the vehicle guidance subsystem), data returned from radar or other ranging sensor, and a flat panel LCD or EL (electro- luminescent) screen to replicate the image which would be seen by a very large (or convex) optical mirror. Unlike optical side view mirrors, the virtual mirror would be located inside the bus. Although mounted inside the bus, it can be configured to mimic a large mirror located away from the bus periphery.

In addition to the virtual mirror, a second collision avoidance technique, the virtual bumper, will be investigated to determine its applicability to this problem. The virtual bumper can be implemented either as an automated system which takes control of steering, throttle, and brakes, or as a direct driver assistive system which provides cues to the driver through the steering wheel, throttle, and brake pedals. For this one-year project, an initial look into driver feedback through the steering wheel will be investigated.

Task 7: Development of Partnerships

Task 7 represents a statewide effort to work with others to initiate a BRT program in Minnesota. The focus is to leverage previous driver assistive technology development at the University as a means to demonstrate improved bus on shoulder performance and to develop innovative collision avoidance systems specifically for buses. To sustain this level of innovation and to eventually find application outside of Minnesota, partnerships with FTA, bus manufacturers, and sensor manufacturers will need to be formed so that additional money can be invested in this research program. Significant work on collision avoidance for the vehicle periphery is needed; this is a difficult problem given the wide variety of conditions under which this system will have to work. The results, however, will be applicable to all transit operators at some level, and provide the transit operator additional protection against losses due to collision.

[Top]

For More Information ...

The project is expected to be completed in mid-2002. More project information is available at http://www.its.umn.edu/research/projects/2001046.html

[Top]