Browsing by Subject "Automatic vehicle location"

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    A Bus Signal Priority System Using Automatic Vehicle Location / Global Position Systems and Wireless Communication Systems
    (University of Minnesota Center for Transportation Studies, 2008-12) Liao, Chen-Fu; Davis, Gary A.; Iyer, Priya
    Current signal priority strategies implemented in various US cities mostly utilize sensors to detect buses at a fixed or preset distance away from an intersection. Traditional presence detection systems, ideally designed for emergency vehicles, usually send signal priority request after a preprogrammed time offset as soon as transit vehicles were detected without the consideration of bus readiness. The objective of this study is to integrate the already equipped Global Positioning System/Automated Vehicle Location (GPS/AVL) system on the buses in Minneapolis and develop an adaptive signal priority system that could consider the bus schedule adherence, its number of passengers, location and speed. Buses can communicate with intersection signal controllers using wireless technology to request for signal priority. Similar setup can also be utilized for other transit-related Intelligent Transportation Systems (ITS) applications. The City of Minneapolis recently deployed wireless technology to provide residents, businesses and visitors with wireless broadband access anywhere in the city. Communication with the roadside unit (e.g., traffic controller) for signal priority may be established using the readily available 802.11x WLAN or the Dedicated Short Range Communication (DSRC) 802.11p protocol currently under development for wireless access in vehicular environment. This report documents the development, verification and validation of the embedded signal priority prototype systems, field testing results and limitations of using the City of Minneapolis Wi-Fi network for Transit Signal Priority (TSP).
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    A High Accuracy Vehicle Positioning System Implemented in a Lane Assistance System when GPS Is Unavailable
    (Intelligent Transportation Systems Institute Center for Transportation Studies University of Minnesota, 2011-07) Arpin, Eddie; Shankwitz, Craig; Donath, Max
    The use of lane assistance systems can reduce the stress levels experienced by drivers and allow for better lane keeping in narrow, bus-dedicated lanes. In 2008, the Intelligent Vehicles (IV) Lab at the University of Minnesota has developed such a system for this purpose. The IV Lab lane-assist system uses dual frequency differential GPS (DGPS) for high accuracy position information. This position information is used in conjunction with a geospatial database containing the road geometry and lane boundary positions required for a lane-assistance system. In urban environments, where tall buildings, overpasses, and other obstructions to the sky are present, DGPS suffers from inaccuracies and outages. This report proposes a method for replacing DGPS sensing with a high accuracy vehicle positioning system which fuses data from RFID (Radio Frequency IDentification) and LiDAR (Light Detection and Ranging) curb detection. A Vehicle Positioning System (VPS) was originally developed by the IV Lab to provide the lane level ("which lane on the road") position of a vehicle with respect to a known reference (i.e., a mile marker or start of roadway) by the use of encoded position information in RFID tags on the roadway, read by the vehicle. The lateral position resolution of VPS is constrained to one lane width, which is insufficient for lane-assistant systems. Thus, in-lane level ("where in the lane") lateral position estimation was supplemented by a LiDAR unit that generates an accurate position of the vehicle with respect to the curb, which is cross referenced with a map database that provides the distance from the lane center to the curb, thus providing the vehicle's lateral offset from the lane center. On-board odometry is used to maintain accurate longitudinal position in between tag reads. By fusing the information from the VPS, LiDAR, and on-board odometry, high accuracy, "where in lane" level vehicle positioning can be maintained from this enhanced VPS during DGPS outages.