National Work Zone Awareness Week (NWZAW): Changeable Message Signs for Highway Construction Areas

Over the past several decades, changeable message signs have taken on an increasingly significant role at highway construction areas across the United States. These electronic traffic control signs (also widely known as variable or dynamic message signs) are now extensively used to alert drivers as they approach work zones to proceed more slowly and carefully through those areas.

A telling indication of the pivotal part often played by changeable message signs for work zones and other potentially hazardous highway situations took place in 2009, when a section (Chapter 2L) specifically addressing these temporary warning measures was included in that year’s edition of Manual on Uniform Traffic Control Devices (MUTCD).

The introduction and use of changeable message signs on highways in the United States can be traced to the mid-1950s. By 1957, such signs were being used to help control the flow of traffic through one of the tubes of the Lincoln Tunnel between New York and New Jersey.

On the New York side, mounted scroll signs displaying a total of three separate three-line messages were used. Those messages were changed via rotating panels inside the sign enclosure. Meanwhile, on the New Jersey side, a rotating drum sign was used to let drivers know when a tube was being used only for traffic heading to New York. The message on the sign was changed to display a “DO NOT ENTER” warning whenever the traffic through that particular tube was traveling into the Garden State instead.

In the years since then, considerable advances have been made with the technological and real-time information capacities of changeable message signs nationwide. In emphasizing the ever-growing applications of such devices, the 2004 Federal Highway Administration publication Changeable Message Sign Operation and Messaging Handbook noted that they “are playing increasingly important roles in attempts to improve highway safety, operations, and use of existing facilities.”

As far back as the 1980s, however, there was already ample evidence that changeable message signs had become well-established mainstays for highway construction areas in various  parts of the country. During the summer of 1988, for example, Maryland transportation secretary Richard H. Trainor gave equal billing to flaggers and their mechanical counterparts when he emphasized the urgent need for safety in highway work zones within that state. Trainor said, “We need all motorists to be cautious and obey all signs and warnings, whether from a flagman or variable message sign.”

Photo Credit: Federal Highway Administration

Additional information on changeable message signs is available at

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