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Traffic Control



The popularity of the automobile in the United States is reflected in some incredible statistics: From 1950 to 1986, the U.S. population increased by 60%, while the number of automobiles grew by 257%. During this same time period, new highway construction declined. The result? Gridlock ! One example is the Hollywood Freeway , built to handle 120,000 cars a day by 1970; in 1965, it was handling nearly twice that amount. In Los Angeles, rush-hour traffic crawls along at 35 mph; if nothing is done to improve conditions, by 2010, traffic will be moving at 11 mph. This kind of congestion was the subject of a Federal Highway Administration study, which found that recurring congestion (e.g., daily rush hours) along urban freeways during 1987 caused 700 million vehicle hours of delay. Non-recurring congestion (e.g., accidents or road work) resulted in over 1.2 million vehicle hours of delay. The costs of national traffic congestion are estimated at $100 billion annually, including lost productivity and accidents. Traffic management can significantly reduce some of these vehicle hours of delay by detecting and responding promptly to incidents and accidents, and rerouting traffic where necessary. A section of Interstate 394 in Minneapolis is about to become the largest live traffic laboratory in the world, using 38 cameras atop poles every 1,000 feet to collect data that is fed to a monitor. This information will be monitored by a computer that can interpret traffic conditions and, ideally, implement a plan to alleviate the tie-ups. Congress has recently appropriated federal funds to, in part, promote a new family of technologies for traffic management, known as Intelligent Vehicle/Highway Systems (IVHS). Several innovative systems are being studied; some, like an automobile navigation system, are already on the market. These navigation systems use compact discs (CDs) to store maps of all U.S. interstate highways and several metropolitan areas. The rest of the system uses speed sensors, an electronic compass, and a small computer. When the driver punches in an address or destination, the computer responds by showing the map on a visual screen, and providing information about the distance in miles and the direction to be traveled.


Predict, count, and project traffic patterns in your community. By studying traffic flow on a local freeway or highway, you will learn how to control variables, formulate a model, hypothesize, measure, predict, and interpret data about traffic. Materials
  • one or more safe spots to view freeways or highways
  • paper
  • pencils
  • chart for data collection
  • stop watch
  • device to measure the speed of a moving car, e.g., a radar gun (optional)
CAUTION: View traffic from safe locations. An adult should be present at all times when students are observing traffic. You may want to coordinate this activity with your local Department of Transportation.
  1. Ask students to think about the issues and variables in designing a study of traffic patterns. Brainstorm as a class, or divide up into groups.
  2. From your master list of ideas, design the parameters of the study (e.g., At what times will traffic be counted? Why those times? For how many minutes will it be counted?).
  3. As the study is being designed, plan a chart on which to record your data.
  4. Divide the students into pairs or groups. Have them write their predictions about what kind of traffic they will encounter before setting out. Then, go count traffic!
  5. When the data have been collected, fill in the master chart with the appropriate information. What did each group observe? How does the information from each group vary?


    Freeman, D.W. (1991) Street smarts. Popular Mechanics (Nov): 33-36.
    Lambert, M. (1986) Transportation in the future. New York: Bookwright
    O'Malley, C. (1991) Electronics as your copilot. Popular Science (Sept):
    Therrien, L. (1990) A gridlock-buster for the 21st century? Business Week
    (Aug 27): 84.
    Zygmont, J. (1992). Intelligent highways. Omni (Jan): 18.
    Additional source of information:
    3M Traffic Control Systems
    Safety and Security Systems Division
    Bldg. 225-4N-14
    St. Paul, MN 55144
    (800) 328-7098
    Community resources:
    Traffic engineer
    State Department of Transportation
    Regional traffic-engineering council