The answer came in the form of a road weather information system (RWIS) provided by Surface Systems Inc. (SSI), a division of Quixote Transportation Technologies Inc., located in St. Louis, Mo.
SHA adopted wind restriction policies to limit the types of vehicles traveling on certain bridges during high winds, and therefore desired more accurate wind data for conditions across the bridge span rather than wind conditions on the bridge approaches.
Two particular situations spurred the decision for a better wind speed monitoring solution. Gregory Welker, District 5 engineer for SHA, said, "In 2003, an unloaded box truck was apparently blown into the parapet wall while crossing the Severn River Bridge (located at U.S. 50 and Maryland Rte. 2, northeast of Annapolis in high winds."
A second incident reported by Welker occurred during flooding caused by Hurricane Isabel, which caused wind sensors on buoys in the river and bay near the Thomas Johnson Bridge (located in southern Maryland) to fail. Since the Thomas Johnson Bridge is used as a connection between two military bases, it became important to know when it was unsafe to transport sensitive military equipment across the bridge.
SHA began preliminary design of a wind monitoring system in fall 2003. It was Craig Fetzer, chief of communications for SHA, who realized that RWIS sites located on both the Severn River Bridge and the Thomas Johnson Bridge were already equipped with anemometers and may hold the answer for a solution.
Using the existing RWIS sites and installing wireless wind sensors, SHA was able to route wind speed data to software as well as vehicle-mounted wind tracker units. This allowed SHA to collect wind data at its central server located at the Statewide Operations Center in Hanover, Md. It also allowed drivers to obtain real-time wind data without having to be in front of the computer.
The vehicle-mounted units are portable and designed to be carried by any SHA vehicle. The installation is simple and only requires the driver to place a magnetic antenna on the roof of the vehicle and plug a power cord into any standard 12-volt accessory jack. The units instantly power up and begin reporting real-time wind speed and direction. The wind sensors and vehicle-mounted units integrated easily into SHA’s RWIS network, enhancing and adding critical weather readings that were not previously being obtained. This solution provided a convenient and cost-effective method for SHA to monitor wind trends and restrict traffic or close bridges when high winds occur. SHA also saved "thousands of dollars" because they were able to use existing RWIS sites and did not have to install additional equipment on the bridge.