Photos have emerged of cars using the Cowgate despite controls in place – some show police vehicles using the busy thoroughfare.
Transport chiefs said both emergency vehicles and residents are among those exempt from the newly launched Summertime Streets limited access.
“It may be that some don’t know about the restrictions in place,” said one driver. “But if some go through it looks like others just follow.
“Summertime Streets has failed before the Festival has even started.”
The flagship Summertime Streets initiative was launched in the Old Town by the city council on Sunday.
Lasting until September 1, it comprises temporary changes on busy streets in a bid to make them easier and safer to walk around.
A partial closure of Cowgate already in place from 10pm each evening has been brought forward to 7pm.
Police vehicles are understood to need non-emergency access to the Cowgate as part of officers’ routine patrolling of its bars and nightspots.
Tory city centre councillor Jo Mowat said she feared traffic problems could become the “theme of the summer” as council staffing cuts take hold.
“I am concerned about the whole Summertime Streets. I don’t think we’re there yet and I’ll be engaging with officers to see what we can do.
“We’ve got a month of this and we’re going to have to do better. I’m worried we’ve made things worse rather than better.”