Pity the poor Conestoga travelers of the 1800s heading west. They had no way of knowing if a band of renegades was around the next bend, or if a herd of bison was ready to thunder their way down the canyon. They had no advance notice of tornadoes, blizzards or golf ball-sized hailstones. In short, they didn’t have the luxury of dynamic message road signs to warn them of impending dooms or delays.
Dynamic message signs — also termed changeable or variable message signs — are programmable traffic control devices that display messages composed of letters, symbols, graphics or all three. They are used to provide information about changing highway conditions in order to improve operations, reduce accidents and inform travelers. These signs may inform drivers to change travel speed, change lanes, divert to a different route or to simply to be aware of a change in current or future traffic conditions.
According to the U.S. Department of Transportation, Office of the Assistant Secretary, there are many levels of such signage, including dynamic message signs, variable message signs, portable dynamic message signs, construction warning signs and portable changeable message signs, to name just a few.
“The most important value of a dynamic sign board is its use as a tool for traffic management operators to alert drivers of an imminent, unexpected life-threatening hazard,” said John McClellan, Minnesota DOT freeway operation supervisor. “A stalled vehicle or crash could be blocking the lane, or the first responders at the scene of that accident — just around the curve or on the other side of the hill. It’s a short, visible, high-profile message that something unexpected is about to happen in the next few seconds, and it doesn’t require anything more for the driver than looking straight out of their front windshield.”
The Regional Transportation Management Center in the Minneapolis/St. Paul area deploys messages for these critical hazards every day, sometimes multiple times a shift. Coupled with a robust camera surveillance system — to assist in confirming and precisely locating the incident — and integration with the state patrol 9-1-1 emergency dispatch and Minnesota DOT F.I.R.S.T. responders, roadway emergencies are prevented from becoming tragedies.
“Less life safety-critical, but still very valuable to the public day-to-day, is providing drivers with additional information to guide their decisions — such as advance warning of closures or unusual delays, and travel times, so drivers can make alternative choices or at least know what to expect,” McClellan said. “That’s what the signs are best at — delivering very short, traffic-related messages in a standard and predictable format for comprehension in the short amount of time drivers have to read them while passing by.”
Minneapolis has several electronic DMSs downtown, which it uses for event parking and for turn prohibitions on certain streets, he noted.
“Everything I’ve heard is that they are happy with them and I see them used whenever I go downtown.”
There’s no question that dynamic message road signs are extremely helpful; not only in emergencies, but also in providing immediate, non-traffic information such as Amber Alerts, Silver Alerts and a host of other pertinent announcements.
Just like anything else, security should be a consideration in the operation and deployment of dynamic messages signs. McClellan said that for the Minnesota DOT, security comes down to strong doors, good locks, knowledge of who has the keys and restriction to high-impact areas.
“The hacking incidents I can think of have been portable message boards left on the side of the road at night, in unlit areas, with the hatch for the keyboard unlocked and a log-in password that’s either the manufacturer default or the hatch itself.”
These are electronic devices, he noted. They need power and a place to be mounted where they are protected from vandalism, theft and damage from vehicles. They need a reliable communications network to program them and verify they are operating correctly, reliable software to control them and appropriately trained staff to operate and maintain them. “But because of their visibility, mistakes or malfunctions will be obvious and well-documented by the public on social media,” he said.
David Rose, communications manager of the Ohio DOT, said his department gained another kind of benefit from the use of dynamic message boards.
“We’ve been successful in using the signs as part of our safety awareness campaign,” he said. “For example, every week we update total traffic deaths on Ohio’s roads as part of our safety awareness campaign. We’ve received very positive feedback and are in our second year of doing this.”
Cheryl Lowrance, principal Intelligent Traffic System engineer with Virginia-based Noblis, handles DMS content and analysis for the U.S. DOT.
“We report benefits, costs and lessons learned on projects that have been deployed based on evaluation, reports and other sources of information,” she said. The benefits included vehicle speeds decreasing significantly in work zones where DMSs were used to inform drivers upstream. The benefit-to-cost ratios for six dynamic message signs on two freeways ranged from 1.38:1 to 16.95:1, based on total crashes; however, hazard warnings posted during incidents were ineffective at reducing secondary crashes. When the link travel times posted on the DMS were twice as long as typical travel times, drivers began to favor alternate routes.
The Ohio DOT worked with several peer departments before building out its ITS, which consists of dynamic message signs, cameras and speed and weather sensors. Statewide, there are 130 message signs, 500 cameras and over a thousand sensors, according to Rose, who added that the message boards are placed mostly around six major Ohio cities — Akron/ Canton, Cincinnati, Cleveland, Columbus, Dayton and Toledo.
“These ITS assets work together to provide real-time traffic data to the public, the media and businesses, all in an effort to reduce congestion and improve safety on Ohio’s highways,” he said.
Resulting data is packaged and presented within www.ohgo.com, the state’s premier traffic website. In addition, ODOT has a centralized Traffic Management Center that operates 24/7, 365 days a year. Its operators are the eyes and ears of Ohio’s transportation system and work directly with law enforcement and first responders to better coordinate and communicate incidents, which are communicated on OHGO.com and through the DMS. TMC operators also work with 22 Freeway Service Patrol responders, who assist with incidents on the ground. In April alone, the FSP responded to 5,620 such incidents, which were mostly a combination of disabled and abandoned vehicles and actual traffic incidents.