User-centered Smart Traffic Sign Development Study

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Date Created
2023-06
Report Number
2023-26
Description
Flaggers protect workers by providing temporary traffic control and maintaining traffic flow through a work zone. They are often the first line of defense to stop distracted, inattentive, or aggressive motorists from intruding into the work area. This project aims to develop an automated intrusion detection system to alert drivers who are unsafely approaching or entering a flagger-controlled work zone. A human factors user needs assessment found maintenance workers preferred a modified traffic signal to feature the alert system due to flagger risks of being in the roadway and drivers failing to stop and remain stopped when presented with the STOP side of the flagger sign. A modified traffic signal that could be operated using a handheld remote was developed. The low-cost embedded electronics on the traffic signal enabled it to track trajectories of nearby vehicles, detect potential intrusions, and trigger audio-visual warnings to alert the intruding driver. Usability testing in a simulated driving test found poor expectancies and stopping rates of the traffic signal-based alarm system compared to a traditional flagger but did demonstrate evidence that drivers may be less likely to stop and remain stopped with the flagger STOP sign than the red ball indicator of the traffic signal. Furthermore, some drivers corrected their initial stopping error after triggering the auditory alarm of the traffic signal. A follow up test found improved performance with the alert system incorporated into an audiovisual enhanced STOP/SLOW flagger paddle. Testing of the developed sensor system found the system capable of simultaneous multi-vehicle tracking (including estimation of vehicle position, velocity, and heading) with a range of up to 60 meters and angular azimuth range of 120 degrees and correctly detecting all test intruding vehicles.

Influence of Autonomous and Partially Autonomous Vehicles on Minnesota Roads

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Date Created
2023-05
Report Number
2023-23
Description
This project focuses on experimental tests of the performance characteristics of autonomous vehicles (AVs) on highways and local roads in Minnesota. The project provides detailed data characterizing AV performance, which in turn can be used to inform the transportation community on implications for infrastructure maintenance, winter road maintenance, work zone guidelines, safety, and traffic capacity. The experimental work presented here makes use of a new autonomous vehicle purchased by the Center for Transportation Studies at the University of Minnesota. The key aspects of the autonomous functions of the vehicle studied in this project include winter performance and implications for road maintenance, characterization of the driving performance of the AV and its likely influence on safety, traffic flow and fuel economy, and the ability of the AV to handle work zones and the implications on changes needed to the guidelines for work zones. The project documents the major challenges and obstacles ahead in the way of true autonomy on Minnesota roads, but also outlines further areas for research with which it will be possible to facilitate the improvement of the capabilities of autonomous vehicles in Minnesota in the future.

Safetruck: Sensing and Control to Enhance Vehicle Safety

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Date Created
1997-12
Report Number
1998-29
Description
This report summarizes the work performed during the 18-month period ending in December 1997. Researchers investigated the use of differential global positioning systems (GPS), inertial measurement, and other sensing technologies as the basis of a system that would prevent crashes. Such a system attempts to control the vehicle if it leaves the lane because the driver is incapacitated. The report includes in its appendices related work on driver fatigue and a bibliography on the effect of drugs and alcohol on driving behavior. The long-term goal of this research involves development of a "driver-centered" vehicle control system capable of providing lane-keeping feedback to the driver, and, if necessary, of imposing aggressive intervention strategies to take over control of the vehicle, steer it to a safe position on the shoulder, and stop it. This research also targets the development of "driver assistive" technologies--such as Heads Up Display and torque feedback supplied by the steering wheel--which provide information to the driver without necessarily requiring computer control of the vehicle. The highlight achievement during this funding period has been the successful demonstration of a GPS-based automated lane-keeping mode of a tractor-trailer on the Minnesota Road Research Project (Mn/ROAD) test track. The report concludes with a strategy for pursuing future deployment.

A Lateral Dynamic Model of a Tractor-Trailer: Experimental Validation

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Date Created
1996-11
Report Number
97-18
Description
The SAFETRUCK program focuses on preventing accidents on rural highways, especially those associated with run-off-the-road incidents and driver fatigue, by giving the vehicle the ability to steer to the side of the road and come to a safe stop if the driver falls asleep or is otherwise incapacitated. Researchers have equipped a Navistar 9400 series class 8 truck tractor with the sensors and control computers necessary to perform this task. Designing the controller that will steer the truck requires a mathematical model of the lateral response of the truck to steering inputs. In this project, researchers developed a lateral dynamic model by incorporating second order dynamics into the steering axle tires. Simulation of the resulting models indicated dynamic behavior that was close to the experimental data for speeds between 15 and 30 miles per hour. This is the first time that a lateral dynamic model of a truck has been experimentally verified. Both models, however, resulted in experimentally determined values for steering axle cornering stiffness that were considerably smaller than published values for the Goodyear G 159 tires on the truck.

Analysis of a Differential Global Positioning System as a Sensor for Vehicle Guidance

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Date Created
1996-09
Report Number
97-17
Description
An ongoing research project examines guidance systems, which can take over control of a vehicle if the driver becomes incapacitated. Part of this project includes an evaluation of a Differential Global Positioning System (DGPS) for vehicle-based lane sensing. This report documents the results of tests of the 5 Hz NovAtel RT20 DGPS receiver. A series of 32 static tests found the overall mean and standard deviation for the offset errors within specifications. In a series of dynamic tests, in which the vehicle was driven around the track at speeds of 20-35 miles per hour, after removing the effect of the GPS receiver's latency, the DGPS determined position exhibited a mean offset error of -17.3 cm (-6.82 in) and a mean standard deviation of 25.5 cm (10.1 in) in the direction of vehicle motion. In the direction perpendicular to vehicle motion, the mean offset was 4.57 cm (1.8 in) with a mean standard deviation of 39.6 cm (15.6 in). With no overhead obstructions in these tests, continuous satellite lock was possible. Tests at higher speeds based on a more accurate methodology are planned for the future.

Improved Approach to Enforcement of Road Weight Restrictions

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Date Created
2013
Report Number
2013-27
Description
This project focused on the enhancement and evaluation of a battery-less wireless weigh-in-motion (WIM) sensor for improved enforcement of road weight restrictions. The WIM sensor is based on a previously developed vibration energy harvesting system, in which energy is harvested from the vibrations induced by each passing vehicle to power the sensor. The sensor was re-designed in this project so as to reduce its height, allow it to be installed and grouted in an asphalt pavement, and to protect the piezo stacks and other components from heavy shock loads. Two types of software interfaces were developed in the project: a) An interface from which the signals could be read on the MnDOT intranet b) An interface through a wireless handheld display Tests were conducted at MnRoad with a number of test vehicles, including a semi tractor-trailer at a number of speeds from 10 to 50 mph. The sensor had a monotonically increasing response with vehicle weight. There was significant variability in sensor response from one test to another, especially at the higher vehicle speeds. This variability could be attributed to truck suspension vibrations, since accelerometer measurements on the truck showed significant vibrations, especially at higher vehicle speeds. MnDOT decided that the final size of the sensor was too big and could pose a hazard to the traveling public if it got dislodged from the road. Hence the task on evaluation of the sensor at a real-world traffic location was abandoned and the budget for the project correspondingly reduced.

Friction Measurement System for Polk County

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Date Created
2013
Report Number
2013-26
Description
A friction measurement system was developed for Polk County and installed on two snowplows in the county's winter road-maintenance fleet. The major components of the developed system were a special instrumented wheel, a pneumatic pressure-controlled cylinder, force-measurement load cell and accelerometers, a data collection microprocessor and a data processing micro-processor. The road friction coefficient was estimated in real-time and was stored on a secure digital card along with the current GPS-sensed location of the truck. The friction coefficient information was also displayed in real-time using LED lights for the operator. Although the basic design of the friction wheel system had been used for several previous years of intermitant testing without showing significant wear, the almost identical installations on the Polk County trucks suffered bearing failures after the first few days of continuous use. The failed bearings were replaced with larger bearings in a more robust mount. Apparently, the system again failed in a few days, but the research team did not learn of this failure until the end of the project. The low budget for the project and the significant travel required to go to Crookston posed major challenges in getting a friction measurement to work effectively for Polk County.

Instrumentation of Navistar Truck for Data Collection

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Date Created
2013
Report Number
2013-01
Description
The overarching goal of this project was to instrument the new MnDOT Navistar truck used at MN Road. A rugged data acquisition, data recording and wireless transmission system was established for collection of various sensor signals from the truck. The truck was instrumented with a suite of 20 accelerometers, with these accelerometers being located both on the five axles of the truck and on the tractor and trailer bodies. In addition, the truck was instrumented with a differential GPS system and an inertial measurement unit in the tractor cab. A cRIO-based data acquisition system, a rugged laptop and Labview software together serve as a flexible platform for data acquisition. A wireless communication system has been established to communicate trigger signals to roadside cabinets when the truck is at desired GPS locations on the road. Data recording by in-pavement sensors is triggered by this system. Software has also been set up for automatic downloading of data from the truck to a server on the network at MN Road. The experimental performance of the developed system has been verified by multiple tests conducted by the research team. The above instrumentation of the truck will enable data collection on truck vibrations, enable analysis of correlations between truck vibrations and variations in signals of weigh-inmotion sensors, and enable recording of truck movements and pavement loads at MnROAD.

Automated Vehicle Location, Data Recording, Friction Measurement and Applicator Control for Winter Road Maintenance

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Date Created
2010
Report Number
2010-07
Description
The first part of this project conducted a detailed evaluation of the ability of a new friction measurement system to provide an accurate measure of road conditions. A system that records friction coefficient as a function of road location was developed using the same vehicle location measurement system as the current MDSS project. Studies conducted show that the friction measurement system provides a significantly more reliable measure of road surface conditions than does visual inspection. The second part of this project focused on a detailed evaluation of the performance of a closed-loop system that utilizes friction measurement for automatic applicator control. Experimental studies have shown that a friction measurement based zero velocity sander can adequately apply salt/chemicals to all slippery spots on a road at speeds up to 25 mph. The final part of this project focused on enhancement of the developed automatic applicator control system with utilization of real-time data from a geographical information system that provides information on upcoming geometric road alignment and known problematic segments of roadway. The developed friction measurement, data recording and applicator control system is compact, modular and can be used on both snowplows and pick-up trucks.

Automated Winter Road Maintenance Using Road Surface Condition Measurements

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Date Created
2007
Report Number
2007-37
Description
Real-time measurement of tire-road friction coefficient is extremely valuable for winter road maintenance operations and can be used to optimize the kind and quantity of the deicing and anti-icing chemicals applied to the roadway. In this project, a wheel based tire-road friction coefficient measurement system is first developed for snowplows. Unlike a traditional Norse meter, this system is based on measurement of lateral tire forces, has minimal moving parts and does not use any actuators. Hence, it is reliable and inexpensive. A key challenge is quickly detecting changes in estimated tire-road friction coefficient while rejecting the high levels of noise in measured force signals. Novel filtering and signal processing algorithms are developed to address this challenge including a biased quadratic mean filter and an accelerometer based vibration removal filter. Detailed experimental results are presented on the performance of the friction estimation system on different types of road surfaces. Experimental results show that the biased quadratic mean filter works very effectively to eliminate the influence of noise and quickly estimate changes in friction coefficient. Further, the use of accelerometers and an intelligent algorithm enables elimination of the influence of driver steering maneuvers, thus providing a robust friction measurement system. In the second part of the project, the developed friction measurement system is used for automated control of the chemical applicator on the snowplow. An electronic interface is established with the Force America applicator to enable real-time control. A feedback control system that utilizes the developed friction measurement sensor and a pavement temperature sensor is developed and implemented on the snowplow.