A controversial new road safety measure that has sparked fierce criticism in recent weeks has seen its first car accident.

A black Vauxhall flipped on its side as it tried to navigate the new width restrictions in Drayton Park, Highbury, on Monday – only seven days after the unconventional layout was completed.

Witnesses said the vehicle was not speeding when it hit the pavement at 7pm and tipped onto a bollard, smashing the passenger window.

Campaigners had already branded the measure a hazard to cyclists and bad for pedestrians.

Caroline Russell, chairman of pedestrian group Islington Living Streets, who spoke to the shaken driver, said: “He just caught the curb at an awkward angle and flipped his car. He was rather frustrated and said the awkward design had contributed to the accident.

“The problem is drivers are being forced to slow down and swerve to the left. They are approaching it at an angle and they are struggling with it.”

The driver was not hurt but his car was stranded for around three hours.

The scheme was installed to calm traffic and stop lorries cutting through from Holloway to Finsbury Park. There are two islands that squeeze traffic up to the edge of the pavement, while only buses and emergency vehicles can pass between the wider middle zone.

John Ackers, of the Islington Cyclists’ Action Group, said: “We really want it ripping out. Pedestrians and cyclists don’t like this and it looks like drivers don’t either.”

Cllr Julie Horten, Lib Dem member for Highbury East ward, said: “I don’t think the signage is adequate and I have concerns about the angle. It’s very tight and I have seen lots of cars only just scrape through that space. Some drivers just stop because they are confused.”

Cllr James Murray, executive member for housing and development, said: “We are monitoring the scheme closely – we have committed to looking at some improvements in response to comments about its design, and we are in regular contact with road safety and cyclist groups about this.”