Traffic lights stopped working at the A47/A15 roundabout near Brotherhood Shopping Park this morning.
The scene was described as “chaos” and an “accident waiting to happen” by onlookers.
One Peterborough Telegraph reader said this was the second morning this week the lights had gone down.
A Peterborough City Council spokesman said: “We were aware of the problem and sent engineers out this morning to fix it. The lights are back on and working now.
“We are just waiting for the fault closure report from the engineer to confirm what the issue was.”