Reports

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.

This research applied wave band and computer vision methods to automatically count vehicle occupants in the High Occupancy Vehicle (HOV) lane at a high level of accuracy. The research showed that use of near-infrared bandwidth offers potential as a method for developing an automatic vehicle occupant counting system. Near-infrared only can produce images when looking through glass, but not metal or heavy clothes, which limits its accuracy in counting children or occupants resting in vehicles. The mid-infrared camera did not produce clear images at highway speeds. The next step involves additional research into a working device that can count vehicle occupants reliably, including analysis of device performance with more types of vehicles, passengers in the back seats, children in car seats, and passengers lying down.

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.

The purpose of this handbook is to provide background information about the importance of pavement preservation and preventive maintenance, as well as present maintenance techniques for a variety of distresses and conditions. The major focus of this handbook is on preventive maintenance activities, which are performed while the roadway is still in good condition with only minimal distress, before the pavement falls into a condition where structural overlays, major milling or reclaiming, or replacement is necessary. The most common flexible pavement distresses are cracking, roughness, weathering, raveling, rutting and bleeding. If the distresses identified in a pavement are related to structural deficiencies, the pavement section is most likely not a candidate for preventive maintenance treatment, and should be scheduled for rehabilitation or reconstruction. Maintenance treatments covered in this handbook include: crack repair w/sealing, including clean and seal, saw and seal, and rout and seal; crack filling, full depth crack repair, fog seal, seal coat, double chip seal, slurry seal, microsurfacing, thin hot mix overlays, and potholes and pavement patching. Tables are outlined giving the most common flexible pavement distresses, along with the best practices for rehabilitation for each. Also given are recommended applications for crack sealers and fillers, surface treatments, and pothole patching. Specifications, technical memoranda and special provisions are included for all treatment methods recommended in the handbook.

This study evaluates the use of seal coating as a method to protect bituminous pavements from oxidation, water infiltration, and raveling. The Minnesota Department of Transportation (Mn/DOT) applied seal coating to a roadway segment of Trunk Highway 21 in August 1998. The report outlines optimal requirements for the application of seal coat. Cost comparisons of the test sections are also presented. Mn/DOT will continue to examine the test strip for performance and provide regular updates until the strip's condition requires reconstruction or overlay.

A laboratory-based linear loading pavement test stand, the Minnesota Accelerated Loading Facility (Minne-ALF) simulates the passage of heavy traffic loads moving at speeds up to 65 kph (40 mph) over small, full-scale pavement test slabs. Hydraulic actuators control a rocker beam, which simulates loads. Researchers simulated the passage of 40-kN (9-kip) single-wheel loads at a rate of 172,000 per day, although wheel loads up to 100 kN (22 kip) can be simulated at varying speeds. Full-axle simulations are possible with frame modifications. Concrete slabs were cast and dowels were installed in slots across cracks/joints. Test variables included joint face texture, repair backfill material, and dowel material and length. Test outputs included measurements of load transfer efficiency and differential deflection across the joint/crack. The effect of joint/crack face texture was great when the joint/crack remained tight. Load carrying performance was improved using Speed Crete 2028 in place of 3U18 concrete backfill with similar joint and dowel bars. Load transfer was unaffected by the use of stainless steel-clad dowel bars in lieu of epoxy-coated dowel bars. Researchers recommend additional testing to examine the effects of dowel length and dowel materials.

In this project, landscape architects, architects, and urban design professionals explored land use opportunities and challenges in the six neighborhood light rail stations of South Minneapolis' Hiawatha Corridor. They studied the Cedar Riverside, Franklin Avenue, Lake Street, Thirty-Eighth, Forty-Sixth, and Minnehaha station areas, analyzing land use patterns, pedestrian and vehicular routes, current zoning, destinations, and potential development sites. They gathered comments from residents in public meetings. Based on the analysis and public feedback, the researchers identified potential development scenarios for each station area. This report summarizes those scenarios.