How SCDOT is trying to keep traffic moving on maxed out roads

Reality Check

South Carolina Department of Transportation engineers say we’re not going to build our way out of congestion, and at this point it is all about maximizing what we have.

“We’re trying to basically bleed every little bit that we can, out of the system that we’ve got,” said Josh Johnson, a SCDOT engineer.

Johnson is the lead traffic engineer in our area. He says, much of that maximizing comes down to signal timing on the main arteries outside of the interstate. 

The SCDOT is using a couple of different systems to time the lights so that you are not caught at every light, but those systems have flaws.

“The situation that causes the system to break down is when we reach that level of capacity where the traffic builds between the signals where that area is full and when the light turns green, and even though they’re green at the same time, you’re waiting on drivers to get going and so and that’s when the system breaks down,” said Johnson. “Even though the signals may be timed well, and even though you may see 3 or 4 green signals in front of you because the road has reached level of congestion it’s really hard to get out of that.”

The DOT also uses an adaptive system that monitors the number of cars on part of Rivers Avenue. That system can adjust the lights to compensate for different levels of traffic. 

“Is it perfect? NO, it’s still not perfect but it’s kind of that next step in trying to manage during those special situations [when the interstate is shut down],” said Johnson.

The major arteries should be re-timed every three years or so. The DOT is admittedly behind that schedule. However, Johnson points to a re-timing on Ashley Phosphate between I-26 and Windsor Hill Boulevard as proof that timing works. He says the recently completed project saves the average commuter one minute on the nine-signal system. 

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