http://www.wistv.com/Global/story.asp?S=11146115
If you drive down any of Columbia's several interstates, then odds are you've seen the digital signs that tell you how long it will take you to get to certain exits or other interstates.
Barbara San Fratello uses them all the time. She also believes them to be quite accurate.
"We travel throughout the state with the agency I work for, so that helps us with trying to meet people on time," said Fratello.
Some call the signs helpful, some call them distracting, and traffic engineers call it the "Intelligent Transportation System."
But have you ever wondered how it works? We asked Department of Transportation Traffic Operations Engineer Tony Sheppard.
He says first, you have to know about several detectors on the road. You can see them on the poles under the DOT traffic cameras and other places along the roadside.
The detectors average vehicle speed from point to point.
"We can actually calculate the time it's taking for someone to travel that distance at any given time during the day," said Sheppard.
That information -- radar and GPS data -- is fed to a computer at DOT headquarters.
The time estimates are within a range and they're supposed to be reasonably accurate as long as you're not driving any faster than the posted limit.
So, we put the sign on Interstate 26 to the test. It says it at a maximum, it will take seven minutes to get to Elmwood Avenue.
We set the cruise control at the speed limit, which changes a couple of times on the way downtown.
Plenty of other vehicles pass us, so unless they get pulled over, they're going to be on the low side of the estimate. Maybe under it.
Well, we made it well under the estimate as well doing the speed limit. It only took us 5 minutes and 35 seconds to get to Elmwood. That's well within the range.
So why do we have the digital boards over the interstates? Turns out the state put up the message boards to warn about traffic hazards and for things like Amber Alerts, but then added the travel times to make full use of the equipment.
"In this information age, we decided it's a good idea to give the information to the motorists so they can make decisions as they drive along," said Sheppard.
Right now, DOT is only using the technology in limited areas around Columbia.
But as more signs go up around the state. more South Carolina drivers will be getting these timely messages.
