Newton's Apple What causes a traffic jam? How can traffic-management systems ease traffic congestion? What will future systems for managing traffic be like? Peggy

Traffic Control

How can technology help alleviate traffic jams?
When Peggy gets stuck in bumper-to-bumper traffic, she goes looking for some answers about traffic management.
Segment length: 7:00

apple Insights

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.i., daily rush hours) along urban freeways during 1987 caused 700 million vehicle hours of delay. Non-recurring congestion (e.i., 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.

apple Connections

1. Why are we so dependent on the automobile? Do other industrial countries have similar traffic problems?
2. Our society places a great deal of emphasis on individualism and freedom of movement. Sometimes, individual rights may conflict with community goals of smooth traffic flow and minimal congestion. How can the two be reconciled?

apple Vocabulary

Dates indicate when the word was first recorded in the English language.

freeways expressways with fully-controlled access (1930)
gridlock a traffic jam in which a grid of intersecting streets is so completely congested that no movement is possible (1980)
highway a main direct road (before the 12th century)
ramp metering a method of controlling the flow of traffic onto a freeway by requiring motorists to wait on the ramp until a green light allows them to proceed
rush hour an ironic phrase defining that period of the day when demands of traffic or business are at a peak (1898)

apple Resources

Freeman, D.W. (1991) Street smarts. Popular Mechanics (Nov): 33-36.

Lambert, M. (1986) Transportation in the future. New York: Bookwright Press.

O'Malley, C. (1991) Electronics as your copilot. Popular Science (Sept): 66-69.

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

apple Main Activity

Traffic Watch

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.



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?


  1. If your students were providing data to a highway engineering department, how often would they have to repeat their counts? Is there a way to automate this process? How might such a system work?

  2. How would you project today's traffic count to future traffic flows?

Try This!

Traffic engineers study many of the issues concerning traffic management: peak periods and recurring congestion; accidents and other incidents; special events; construction- and maintenance-work zones; inclement weather; and catastrophic events. Invite a traffic engineer to your class to discuss traffic in your community. How does your community "encourage" traffic to space itself more evenly during the day?

Try This!

Some traffic signals are timed to help clear congestion and keep the arteries moving at a regular pace. Ask someone you know who has a driver's license to drive you down a street in your community that might have timed signals. Can you figure out the optimum speed for traveling with all green lights? Some streets have signals timed so that cars don't always get a green light. Why would traffic engineers want to time the lights this way?

Try This!

Statistics abound when looking into traffic issues. For example, in 1900 there were 8,000 autos and trucks in the United States; in 1929, there were 23,000,000 vehicles; and in 1981, there were 160,000,000 passenger cars, trucks, and buses. Work with your librarian to find more statistics. How many miles of roads are there in the United States? How many additional miles are added each year? How many accidents were there 10 years ago in your metro community? How many were there last year? How many cars per person are there in China? How does this compare with the ratio in the U.S.? In your family? Design several graphs to present your information.

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