Dynamic Message Signs: Travel Times and AMBER Alerts

May 29, 2013 by

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Electronic Sign

You’re running late to work — again — and the highway is at a crawl. Will you ever make it? Luckily, there’s an electronic road sign up ahead — only 15 more minutes until your exit, it reads. Saved by the sign!

Another day, you’re driving down the interstate when you see a message broadcast on another road sign. “AMBER Alert!,” it says. It gives the description of a car so that hundreds of drivers on the interstate, as well as all the people listening to local TV news and radio broadcasts, know to be on the lookout for the vehicle.

Road signs have come a long way from their origins, the stone markers of Roman times. Of the hundreds of years of road sign history, electronic road signs, also known as dynamic message or variable message signs, have only been around for about the last three decades.

Dynamic road signs started out as diesel-powered machines using small light bulbs to spell the words. In the 1980s, signs that used flip dots became popular. These signs used an electromagnetic field to flip the dots, which were black on one side and fluorescent green on the other, to create messages. Then, in the 1990s, companies began using light-emitting diodes, or LED, technology, which is still used today.

Transportation officials control the signs, alerting drivers to construction work, an accident blocking traffic, detours, dangerous weather conditions and more. For example, if an accident or a disabled vehicle is obstructing traffic, dynamic message signs can guide drivers toward open lanes. If an area is experiencing bad weather, the signs might warn motorists about ice and snow in wintry weather, fog and strong winds, as well as mudslides or falling rocks.

Technology allows officials not only to update the signs, but also to keep track of the traffic flow in order to use the signs to advise drivers about travel times. How do they do that? Well, for example, in Colorado, if a car has an electronic toll tag, like an E-ZPass, sensors are used to find out how fast it is actually traveling, according to the Colorado Springs Gazette. These sensors also estimate how many cars are on the road, and as data is collected, a formula is used to identify and remove data on cars that have longer travel times (for example, if the driver stopped for food or coffee). The results are updated frequently and displayed on electronic signs, which give travel time estimates.

In addition to warning drivers about hazards or slowdowns ahead, law enforcement officers also use the signs as a tool to help find missing children via the AMBER Alert system. AMBER Alert — which stands for America’s Missing: Broadcast Emergency Response Alert — notifies state transportation officials and media outlets about a missing child. When an AMBER Alert occurs, information is displayed on electronic highway signs, which often includes the car’s make, model, color and license plate number.

The Department of Justice reports that overall, AMBER Alerts have helped lead to the recovery of 621 abducted children in the U.S., and that children are often released when the adults with them learn that an alert has been issued. So in the case of the AMBER Alert, the electronic signs are not only used to give out important information, but they can also help drivers to do a good deed by reporting sightings of abducted kids.

Today’s dynamic message signs provide valuable information that can make for a more pleasant driving experience and can even save lives. Technology has made huge strides in the last century. What sign innovations do you predict for the next 100 years?

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Melissa

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