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Snowplow operators are often tasked with clearing snow from roadways under challenging conditions. One such situation is low visibility due to falling or blowing snow that makes it difficult to navigate, stay centered in the lane, and identify upcoming hazards. To support snowplow operators working in these conditions, University of Minnesota researchers developed a snowplow driver-assist system that provides the operator with visual and auditory information that is suitable for low-visibility situations. A lane-guidance system uses high-accuracy Global Navigation Satellite System (GNSS) and maps of the roadway to provide information to drivers about their lateral positions. A forward-obstacle-detection system uses forward-facing radar to detect potential hazards in the roadway. The design of the system, and in particular its interface, is guided by extensive user testing to ensure the system is easy to understand, easy to use, and well liked among its users. The system was deployed in two phases over the 2020-2021 and 2021-2022 winter seasons. In total, nine systems were deployed on snowplows across Minnesota, four in the first winter season and an additional five in the second. Participating truck stations represented all eight MnDOT districts as well as Dakota County. Over the course of the deployment, additional user feedback was collected to identify system strengths and areas for improvement. The system was found to be a cost-effective addition to snowplows that increase driver safety, reduce plow downtime, and increase driver efficacy for plowing operations, thus providing support to operators working in demanding, low-visibility conditions.

Recent advances in MIMIC (Millimeter Monolithic Integrated Circuit) radar technology play an important role in the development of automated highway systems and automated vehicle control systems. This report presents results of a preliminary investigation into MIMIC-based automotive radar technology and makes recommendations for hardware evaluation. MIMIC technology integrates much of the radar transmitted, receiver, and signal processing hardware onto a one- or two-piece chip set. Massive integration leads to lower manufacturing costs and lower product costs. Moreover, this integration reduces the size of hardware, allowing the radar components to be installed in the vehicle without the need for significant modifications. As radar systems become smaller and cheaper, the demand for these systems will increase. Radar systems affect both the vehicles so equipped and other vehicles within a reasonable proximity. Before vehicles equipped with radar systems travel on public roads, their effects on traffic flow and highway safety must be investigated so that proper regulations can be developed and enforced.

With interest in collision avoidance technology for highway vehicles on the rise, this report presents an overview of current collision avoidance technology, the technical work required to bring these systems to a commercially viable product, and the societal issues that need addressing before wide-scale deployment can occur. Many questions remain about the benefits of deploying such systems, the costs, the effect of these systems on drivers, and the steps necessary to effectively regulate vehicles equipped with such systems. In addition to technical aspects, the report also discusses the issues that society will face during development and deployment of these systems, which may prove bigger impediments to deployment than technical issues. The report also recommends a research plan to perform fair, unbiased evaluations of emerging collision avoidance technology.

This report describes the development of technologies that safely steer a vehicle if the vehicle's driver becomes incapacitated. A Differential Global Positioning System (GPS) senses the vehicle's position and velocity. This method seems to offer adequate precision with a low-enough infrastructure cost to make the system practical in most rural settings. Researchers used a heavy vehicle -- a class 8 truck tractor -- partly because of the most favorable economics associated with installation of this type of system on a commercial vehicle, and partly because of the commercial driver's higher exposure to conditions that engender drowsy driving. This research examines two potential applications of the steering, throttle, and brake controllers. The first, a virtual rumble strip, vibrates the wheel whenever the vehicle drifts out of its lane. The second, a system that monitors driver steering performance, senses the erratic steering that presages loss of consciousness and then takes control of the vehicle, pulling it over to a safe stop.

This report describes results from a series of experiments using the virtual bumper collision avoidance algorithm implemented on a Navistar tractor cab. The virtual bumper combines longitudinal and lateral collision avoidance capabilities to control a vehicle in normal and emergency situations. A programmable boundary, the virtual bumper, defines a personal space around the host vehicle. Researchers used a radar and a laser range sensor to sense the location of vehicles in front of the truck. Target vehicles that enter the truck's personal space impose a virtual "force" on the host, which in turn modifies the vehicle's trajectory to avoid collisions with objects in the field of view. Researchers tested the virtual bumper longitudinal controller under different driving situations and at different speeds. The experiments included several scenarios: Adaptive Cruise Control, the truck performing a critical stop for a stationary target vehicle, and situations that simulate stop-and-go traffic. Results from the virtual bumper longitudinal experiments were favorable. The algorithm demonstrated robustness to sensor noise and the ability to maintain a safe headway for both normal and emergency driving scenarios. Researchers currently are improving the sensing technology and incorporating a road database, which contains roadside features to greatly reduce, if not eliminate, false target detection.

A comprehensive driver assistive system which utilizes dual frequency, carrier phase real time kinematic (RTK) differential global positioning system (DGPS), high accuracy digital geospatial databases, advanced automotive radar, and a driver interface with visual, haptic, and audible components has been used to assist specialty vehicle operators perform their tasks under these low visibility conditions. The system is able to provide a driver with high fidelity representations of the local geospatial landscape through a custom designed Head Up Display (HUD). Lane boundaries, turn lanes, intersections, mailboxes, and other elements of the geospatial landscape, including those sensed by automotive radar, are projected onto the HUD in the proper perspective. This allows a driver to safely guide his or her vehicle in low to zero visibility conditions in a desired lane while avoiding collisions. Four areas of research, are described herein: driver assistive displays, the integration of a geospatial database for improved radar processing, snowplow dynamics for slippery conditions, and a virtual bumper based collision avoidance/gang plowing system. (Gang plowing is the flying in formation of snowplows as a means to rapidly clear multilane roads.) Results from this research have vastly improved the performance and reliability of the driver assistive system. Research on the use of a specialized driver assistance system to assist specialty vehicle operators in low visibility conditions, including the design of a custom Head Up Display (HUD) projecting elements of the landscape in proper perspective. Driver assistive displays, the integration of a geospatial database for improved radar processing, snowplow dynamics for slippery conditions, and a virtual bumper based on collision avoidance/gang plowing system are discussed.

A driving simulation experiment was conducted to investigate auditory icons as side- and forward-collision avoidance warnings. The auditory warnings produced significantly faster mean response times than with no warning, and participants preferred a double-beep side collision warning over a single-beep warning. Researchers recommend a double-beep auditory warning similar to the double-beep of a car horn for side-collision avoidance and a forward-collision avoidance warning similar to two successive bursts of screeching tires.

The main goal of this research was to develop the system requirements for the global positioning system (GPS) and the digital map components that make up the core of an in-vehicle road user charging system. The focus was to evaluate both GPS and digital maps in the most difficult of environments - where roads of different jurisdictions and possibly different fee structures are located in close proximity to each other (a highway and a frontage road, for instance). In order for the system to be effective it must be able place the vehicle on the correct road. GPS receivers that are commonly used by automotive navigation systems do not have sufficient accuracy for road user charging applications. However, the GPS-determined positions can be corrected, and thus made more accurate, using publicly and privately available wireless signals, namely, using differential GPS (DGPS). This experimental study, based on road testing, found that only certain DGPS receivers are capable of achieving the needed accuracy. Extensive testing of existing digital maps found that they are also not accurate enough to be used for road user charging. There are however, new, higher accuracy digital maps (not yet publicly available) that are already being used for vehicle safety applications. By combining DGPS and such high accuracy digital maps, the ability to design a road user charging system with high geographical resolution can become a reality.

This report documents the evaluation efforts undertaken by the Minnesota Team. To complement the work undertaken by the independent government evaluator, Battelle, the Minnesota evaluation team focused on two specific areas of the evaluation: human factors and benefit-cost analyses. Human factors issues include driver acceptance, reduction in driver fatigue, the effectiveness of the driver interface, and the measurable changes in driver performance. The Driver Assistive System (DAS), which is under evaluation for the US DOT Specialty Vehicle Generation Zero Field Operational Test, is designed to provide a driver a means to maintain desired lane position and avoid collisions with obstacles during periods of very low visibility. This program is motivated by the fact that specialty vehicles often must operate under inclement weather conditions and associated low visibility situations. The DAS improves safety for the specialty vehicle operator by providing the necessary cues for lane keeping and collision avoidance normally unavailable during poor visibility conditions. The DAS may also improve safety conditions for the general public by facilitating all-weather emergency services, and in the case of snowplows, opening roads and keeping them passable in heavy weather for other emergency vehicles and the general motoring public.

The objectives of this assessment are: to estimate the potential benefits of the Driver Assist System (DAS) for winter maintenance activities; to assess and describe the potential market for the DAS technologies as well as the approximate price point at which the system would be commercially viable, and; to determine where, geographically, DAS technology would be most cost-effective. The findings presented in this report are based on information that was gathered through an extensive literature review and a series of interviews conducted with state and county maintenance engineers and supervisors, equipment vendors, system integrators, equipment procurement personnel, and individuals involved in various aspects of risk management for transportation agencies. The expected benefits of DAS on winter maintenance vehicles include the reduction in travel times, less disruption to routine travel behavior and improved safety for the traveling public during and immediately following winter weather events. Winter weather events have a substantial impact on traveler safety, economic activity, and transportation maintenance costs. The functional objective of the DAS is to provide snowplow operators a means to operate snowplows during periods of low visibility. The study assesses the issue of visibility from the perspective of both snowplow operators and maintenance engineers.