A car was left stuck on top of a set of metal bollards that rose in Cardiff city centre.
Josh Elton, 28, and his father, 59, from Cardiff, were driving in two separate vehicles down a side street on their way to a charity event when they approached the bollards.
The father pressed the button to lower them and said he told the person on the intercom there were two cars.
When the 28-year-old followed his dad, the bollards raised, trapping his car.
"Dad went up to the bollards first and spoke to the person on the intercom saying that there's two cars, they said 'no problem'," Mr Elton said.
"I start going through after him and then the bollards lifted the front of the car."
"Afterwards, the person on the intercom said that they have to go through one at a time," he added.
The 28-year-old said the damage could cost up to £1,300.
A spokesman for Cardiff Council said: "There is a clear sign on the approach to all security bollards, advising motorists to stop their vehicle, only proceed when the green light shows and specifically not to tail-gate vehicles through the barrier.
"The bollards are designed to lower and rise out of the ground as quickly as possible to stop unauthorised vehicles driving through the security cordon.
"For the reasons clearly shown in the photographs taken on Wharton Street, we would advise all motorists not to try to tail-gate authorised vehicles through these bollards."