The proposal, which was originally approved last week, would have allowed sheriff's deputies to send speeding tickets to drivers without pulling them over.
Commissioners voted 5-4 last week to approve the purchase of the cameras, but three commissioners said they had changed their minds by the next day after hearing opposition from the public.
On Wednesday, the commission voted again on the measure, which failed 8-1.
Only Commissioner Greg Beck, who proposed the idea, voted for it.
He said the cameras would allow officers to catch speeders in areas where it would be unsafe to make a traffic stop.
"This is for officer safety on the narrow roads, and this is for school zones, so it's the safety of the kids going to school up in the county," Beck said. "That has not changed in a week of phone calls."
Commissioner Jim Fields, who changed his vote, said that while traffic stops can be dangerous for officers, making contact can have other public safety benefits.
"Officers, once they stop a vehicle, often discover other crimes being committed," Fields said.
Under the proposal, the county would have entered into a contract with Brentwood-based Applied Technology Partners, which would have supplied the cameras and sent out civil speeding tickets to the car's registered owner.
In an interview, company President John McConnell said the most recent vote was disappointing.
"Obviously, we are very disappointed that we will not be able to serve the citizens of the community," McConnell said. "And we still think it's a very viable speed management tool."
Information from: Chattanooga Times Free Press.