Advanced Snowplow (ASP)
Vehicle Control

Han-Shue Tan
Associate Research Engineer, California PATH

In 1998, PATH started an Advanced Snowplow project with the California Department of Transportation (Caltrans) and the Advanced Highway Maintenance and Construction Technology Center (AHMCT) at UC Davis. The project consists of three phases:

  • Advanced Snowplow Development and Demonstration (ASP-I)
  • Development of an Advanced Snowplow Driver Assistance System (ASP-II)
  • Rural Field Test of the RoadView System

    The Caltrans ASP is applying PATH's magnetic guidance system to help operators drive the plow even in a total whiteout by providing a visual display inside the cab of the plow's position relative to the sides of the road and to potential obstacles. A conventional snowplow (International Paystar 5000 ten-yard sander truck with front blade and wingplow) was modified to include:

  • a computer data acquisition and information processing unit
  • sensors for measuring steering angle and vehicle movements
  • sensors for measuring the field of magnetic markers installed in the roadway
  • radar sensors for obstacle detection
  • human-machine interface (HMI).

    snowplow snowplow

    Two primary technologies are being used in the ASP: detecting the plow's position relative to the center of the lane, to assist the operator in steering; and detecting obstacles, for collision warning. PATH's magnetic marker guidance system provides guidance information. This system was developed for automated vehicle guidance and control applications. A single magnetometer array comprised of seven magnetic sensors was installed at the front of the snowplow. Signal processing of the magnetometers provides lateral position measurement relative to the center of the lane, longitudinal position relative to mileposts, and yaw angle estimate. Binary coding of the magnetic markers when installed (north pole up vs. south pole up) also provides information about roadway characteristics, e.g. the direction and radius of the curves. The obstacle detection system uses a commercially available Eaton-Vorad radar, incorporating a digital interface developed by AHMCT in conjunction with Eaton Vorad.

    The HMI development was a combined effort of PATH human factors and control engineers, with significant input from snowplow operators. The preliminary design of the HMI uses a LCD panel to dynamically display current and projected vehicle position relative to the desired path. Roadway characteristics are obtained through position updates from the magnetic guidance system, and the current and projected positions of the vehicle are processed using the lateral position measurements. Potential obstacles, as well as relative vehicle spacing, are obtained from the radar system. The display has two separate components: lateral (right hand side) and forward obstacle (left hand side). It is to note that the forward obstacle component is independent of the lateral component and that it will work when the snowplow is not over magnets.

    HMI Lateral Component

  • Two white road lines are the boundaries of the sensor limits (2 meters), shows road curvature.
  • Rectangle block on the bottom is the current snowplow position.
  • Top rectangle is the predictor, which is the future position of the snowplow 20 meters ahead. To drive to the road center, move the predictor to the center tick by moving the steering wheel. The current position marker will move over slowly.
  • Three ticks on the top and bottom are 2 feet apart.
  • Nickname of the road section is shown at the bottom.

    Color coding represents the trust level of the lateral system:

  • No road display = not reading magnets.
  • Yellow rectangles and road lines = reads the magnets but does not know the road geometry, trust level is medium.
  • Red rectangles and white road lines = reads the magnets and knows the road geometry (through the coding), trust level is the highest.
  • Gray rectangles and road lines = not reading magnets (recent), a yellow arrow will point towards the lane center. If condition persists, the display will disappear after a short while.

    Forward Obstacle Component
  • Each bar shows the closest target in the left, center, and right lanes with respect to the plow.
  • Bar colors will change as target gets closer (yellow to orange to red).
  • The range of this display is 300 feet.
  • The distance of the closest of the three targets is shown in numbers at the bottom (in feet).

    Over a span of three years, PATH and AHMCT equipped three Caltrans snowplows with the steering guidance system: 7005, 7228 and 8467.


    PATH has three different implementation sites, where magnets were installed in the lane center at 1.2 meter spacing.

    Kingvale Flagstaff Burney

  • Donner Summit on I-80 (Lake Tahoe), CA. (7239 feet)
    Ten miles of magnets were installed on the eastbound and westbound of Interstate 80 over Donner Summit in the Sierra Nevada, which often gets more snowfall than any other road in the lower 48 states. The C7005 snowplow has been used by the Kingvale maintenance yard over Donner Summit since 1998.

  • Kendrick Park on US-180 (Flagstaff), AZ. (7000 feet)
    Six miles of magnets were installed on the northbound and southbound of US Highway 180, about twenty miles north of Flagstaff near the San Francisco Peaks, Arizona's highest mountains. Since 1999, the C7005 snowplow is sent each spring to Flagstaff for the system to be evaluated by Arizona DOT operators.

  • Hatchet Mountain Pass on Route 299 (Shasta), CA. (4366 feet)
    Ten miles of magnets were installed on the eastbound and westbound of Route 299, about 60 miles southeast of Mount Shasta. The C8467 snowplow is stationed at Burney maintenance yard and has been used there since 2001.


  • Software: Han-Shue Tan, Bénédicte Bougler, Paul Kretz
  • Hardware: David Nelson, Bart Duncil
  • Human Factors: Aaron Steinfeld, Joanne Lins


  • Demo '99 in East Liberty, OH. July 26-28, 1999.
    Simulation of the steering guidance system on the C7005 snowplow: guests can move the steering wheel and "drive" the plow using the HMI screen as if they were on the magnets.

  • Rural ITS Conference in Flagstaff, AZ. August 29-September 1, 1999.
    Simulation of the steering guidance system on the C7005 snowplow.

  • CAATS Conference in Sacramento, CA. September 12-15, 1999.
    Simulation of the steering guidance system on the C7005 snowplow.

  • PATH, AHMCT and Caltrans workshop at Kingvale, CA. October 15, 2003.
    Simulation of the steering guidance system on the C7005 snowplow.


    Magnetic Snowplow Testing
    Kingvale, January 1999
    Flasgtaff, April 1999

    1.47 min


    H.-S. Tan and B. Bougler, "A Snowplow Steering Guidance System using Roadway Markers - Problem Formulation and Solution Concept," Vehicle System Dynamics, vol. 32, no. 1, July 1999, pp. 3-22.

    H.-S. Tan, B. Bougler and P. Kretz, "A Steering Guidance System for Snowplow - An Interesting Control Problem," Proceedings of the 38th IEEE Conference on Decision and Control, Phoenix, Arizona, USA, December 1999, pp. 5114-19.

    Article in the Williams-Grand Canyon News published the week of March 22-28, 2000, no.12: "Magnets lead snowplow through storms", by Nok-Noi Hauger.

    H.-S. Tan, B. Bougler, A. Steinfeld and P. Kretz, "Snowplow Steering Guidance Display - Design and Validation," Proceedings of AVEC 2000, 5th International Symposium on Advanced Vehicle Control, Ann Arbor, Michigan, USA, August 2000, pp. 531-537.

    Article in the Public Roads Magazine published in January/February 2001, vol. 64, no. 4: Safe Plowing - Applying Intelligent Vehicle Technology by Robert A. Ferlis, Shahed Rowshan, and Cathy Frye.

    A. Steinfeld, H.-S. Tan and B. Bougler, "Naturalistic Findings for Assisted Snowplow Operation," Proceedings of Human Factors and Ergonomics Society 45th Annual Meeting, Minneapolis, Minnesota, USA, October 2001.

    Article in the San Francisco Chronicle published on October 29, 2001: Highway work going high-tech - UC Davis constructs futuristic equipment by Michael Cabanatuan.

    H.-S. Tan, B. Bougler and A. Steinfeld, "Snowplow Steering Guidance With Gain Stabilization," Vehicle System Dynamics, vol. 36, no. 4-5, November 2001, pp. 279-305.

    Article in the Oakland Tribune published on December 25, 2001: "Computers guide experimental plows", by William Brand.

    Article in the Contra Costa Times published on December 28, 2003: "High-tech tools guide snowplows in clearing state's wintry highways", by Lisa Vorderbrueggen.

    Front page of Caltrans CT News, volume 5, issue 1 of January 2004: "High-Technology Snow Removal".

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