Portable Variable-message Signs
Truck-mounted VMSes are sometimes dispatched by highway agencies such as Caltrans to warn traffic of incidents such as accidents in areas where permanent VMSes aren't available or near enough as a preventative measure for reducing secondary accidents. They are often deployed in pairs so that the second VMS truck can take over when the traffic queue overtakes the first truck, forcing the first truck to circle around and mobilize itself further upstream from the queue where it is effective. An optional third truck, the team leader, may be utilized for driving by and monitoring the incident itself, traffic patterns and delay times, in order to make strategic decisions for minimizing delays—analogous to spotter planes used in fighting forest fires.
Trailer-mounted variable-message signs are used to alter traffic patterns near work zones, and for traffic management for sporting events, natural disasters, and other temporary changes in normal traffic patterns. The messages displayed on the sign can be programmed locally on the unit's control panel, or units equipped with a cellular modem can be programmed remotely via computer or phone. Most manufacturers produce trailers which comply with the National Transportation Communications for Intelligent Transportation System Protocol (NTCIP) which allows the portable trailer to be integrated with an intelligent transportation system. Trailer-mounted VMS can be equipped with radar, cameras, and other sensing devices as part of a smart work zone deployment.
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Sign on Interstate 880 in Oakland, California.
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Variable message sign warns "Avoid London - Area Closed - Turn On Radio" following the 7 July 2005 London bombings.
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Europe's largest Dynamic Route Guidance System Nuremberg, Germany.
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A Variable Message Board on National Highway 4, In Bangalore, India.
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Variable Message Board on an interchange of a German Autobahn.
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