By Dave Vieser.  It looks like the new toll lanes on I-77 will be only 17 inches thick, not 32 inches like the general purpose lanes. The thinner pavement is based on the fact that the toll lanes will not be used by trucks.

The difference in pavement thickness is outlined in the contract between the NCDOT and Cintra. It calls for a 32 inches for the GP lanes, including an aggregate base and a sub-grade, while the toll lanes will be a grand total of 17 inches thick, with no sub grade.

It’s not like there’s a problem, or is there? The chairman of the Lake Norman Chamber, among others, say that since the cheaper, thinner toll lanes  don’t allow semi-tractors, truck traffic will intensify on the general purpose lanes.

“According to the credit rating agencies the toll lanes are expected to carry 4-6 percent of total traffic when they open, escalating to 10 percent,” said Mike Russell, chairman of the Lake Norman Chamber of Commerce. “These estimates imply that the toll lanes will be underutilized as compared to the general purpose lanes, meaning truck traffic will increase congestion in the two general purpose lanes and our commerce and quality of life will suffer.”

As I-77 motorists know already, the large trucks which use the interstate are much slower to accelerate, thereby creating more congestion potential for the general purpose lanes, especially in stop-and-go traffic.

Dr. David Hartgen, Transportation Professor at UNC, says the difference in pavement thickness itself “is not out of line.” However, he raised some other concerns.

“The use of a thinner pavement for the toll lanes probably precludes their use by heavy trucks in the future, unless the lane pavements were strengthened. In addition, if the estimates of traffic are low, then the pavement may not last the full design life, leading to an unplanned rehab need at some point in their life.”

Also of concern is the impact the CATS Express buses, which would be permitted to use the toll lanes, could have on the thinner pavement.

So, while the thickness of the new lanes appears to be technically consistent with the requirements outlined by the American Association of Highway and Transportation Officials, questions remain about the future should the project default or if the state decides to open the lanes to truck traffic, Russell said.

A spokeswoman for the I-77 Mobility Partners could not be reached for comment.