Construction barriers on the St Crispins flyover will be secured after blowing down twice in high winds.

During the second incident around 5.40pm on Monday evening, a stretch of the barriers toppled onto two cars which were passing at the time.

One was being driven by 32-year-old Paston College lecturer Dean Mooney.

'I was approaching the roundabout where it all merges into one lane when the barriers just started to go,' he said. 'It was just a gust of wind and I thought there was no way it was going to topple but the whole thing just came crashing down.

'I tried to move over and it felt like Indiana Jones trying to accelerate through it before it came down.'

Mr Mooney's car has damage to the mirrors, windows and wipers, and he admitted 'it could have been a lot worse'.

'If a cyclist had been right there at the time they would have been crushed,' he added.

'The fences were on top of bollards and there was no water or sand weighing them down. I'm more concerned that if it has happened twice now it was never addressed the first time.'

Transport for Norwich workers have admitted only half the bollards were weighed down with water at the time. All will now been filled after the incident on Monday.

The barriers have been erected as £900,000 of work is ongoing to create a pedestrian and cyclist crossing over St Crispins Road.

Jeremy Wiggins, Transport for Norwich manager, said: 'From experience, we now know that this site suffers from wind being funnelled between buildings. Calvert Street, on the south side, is bordered by high buildings which funnelled a strong southerly wind we had a few weeks ago and knocked over the barriers.

'Monday night, there was a strong northerly wind, which was funnelled between the HMSO building and Surrey chapel.

'The barriers are the heavy, water filled type, which are about 130kg each when filled with water. Initially, every other barrier was filled with water. We have now instructed site operatives to fill every barrier with water, particularly where the wind is now known to concentrate. Additionally, barriers will be topped up with water where appropriate to maximise their weight. We will monitor the situation going forwards, particularly when windy weather is forecast.

'We apologise for the inconvenience caused.'