We may never know who hit the I-75 South bridge, causing it to collapse on I-24 and hurting a passing driver.

That driver's condition is improving.

Channel 3 learned Wednesday, the cameras that monitor the I-24/I-75 split and the entire statewide highway system do not record video.

Channel 3 also learned there is no agency actively searching for the driver who engineers said hit the beam and caused it to fall on the interstate below.

It's like finding a needle in a haystack, troopers said.

Tennessee Department of Transportation spokesperson Jennifer Flynn tells Channel 3, TDOT is relying on the Tennessee Highway Patrol to let them know if they find the driver.

THP Sgt. Alan Bailey said troopers checked the nearest weigh station on I-24 in Manchester the day of the crash.

"Because any over-sized load that comes to the Manchester scales has to stop. And we asked them if they had any over-sized loads come through with some damage and they said no," Bailey added.

Bailey directed Channel 3 to the Chattanooga Police Department for updates on the search for the driver.

But CPD spokesperson Elisa Myzal said her department is only handling the crash involving the car and not what caused to collapse.

C. Mark Warren is a person injury attorney in Chattanooga. He does not have any ties to the collapse.

Warren said if a driver with an over-sized load hit the bridge, it should have been reported.

"The truck driver should have self-reported the incident to his company, and the company should have reached out to TDOT about what happened to the bridge. But it's basically up the the company to self report this to TDOT," Warren said.

There are 59 TDOT SmartWay cameras monitoring Chattanooga highways.

Officials said they only show real time traffic conditions and do not record or store video.

So there is no video record of the bridge being hit, only the evidence engineers said they found pointing them to their findings.

"The purpose is not to investigate accident. If you think about it, there's so many TDOT cameras in Tennessee, it would be burdensome to try and maintain all the video tapes of those cameras 24/7, seven days a week, 12 months a year," Warren said.

Their purpose is to monitor road conditions, not collect evidence for investigations. But even if video did exist, it's not clear who would lead an investigation into finding the driver.

Flynn said there is a chance that whatever hit the bridge was not permitted, meaning there would be no record on file with TDOT.

If a driver is located, they could be charged with failure to report or leaving the scene of an accident involving property damage.

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