It won't cure every traffic headache, but Dallas' new Intelligent Transportation System (ITS) is helping the Texas Department of Transportation (DOT) better manage the traffic flow on its freeways. Cameras mounted strategically along the roadways send video streams over fiber to communications "hubs" that then route the video traffic and data to one of a series of ATM-based "satellite" stations. These ATM sites are connected to one another at OC-12 speeds and to the DOT's control center. That's where engineers analyze traffic patterns and track slowdowns or accidents on the roadways. They also alert police to problems and eventually will be able to contact other emergency services about accidents.
The Texas DOT in Dallas chose ATM for the core of the ITS network, but will be expanding its applications for commuters over the Web. That would, of course, eventually extend to cell phones and other hand-held devices with wireless Internet access, too. "We would host a Web server so commuters could look and see where the accidents are and the current speed along the highways," says Robert Bacon, ITS design engineer for the DOT Dallas District. Aside from the video cameras, there are vehicle detectors that monitor speed and volume of the traffic and message boards posted for drivers.
Bacon says the DOT chose ATM for bandwidth reasons and for the ability to configure the network into a ring for rerouting among the satellite stations. The department initially planned to use RF modulation, but the radio model was too cumbersome with its point-to-point configuration, and ATM's ring features made more sense. The trade-off, however, was that the DOT's ATM vendor, Marconi Communications, uses a proprietary video-compression technology called Motion JPEG rather than the MPEG2 standard. Still, the rub with video products is that even with a standard, interoperability is no guarantee. "Even different manufacturers' MPEG2 codecs are still not compatible with one another," Bacon says.
The next generation for ITS is IP-networked automobiles. "Some are being designed to give directions, traffic information and road guidance. We would look to have them tie into our network so a car could calculate the best route and avoid [slowdowns caused by] accidents," Bacon says. "We would have servers from our control center pumping this information to the satellites, which would then feed it to the cars."
Texas has led the way in intelligent highway technology--nearby Fort Worth has built a system similar to Dallas' ITS that will eventually interface with it. San Antonio and Houston have such systems, and Austin and El Paso have them in the works. About 32.5 miles of Dallas' highways are networked so far, with another 11 miles under construction and more to come in the next year or so.
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