Work on the £178.5m Norwich Northern Distributor Road has been delayed so that BT Sport customers can watch the World Athletics Championships.
The B1149 Holt Road had been due to be closed permanently south of Horsford from Monday, as part of the work connected with the NDR.
But BT has refused to allow its cables, which need to be diverted over a new bridge, to be moved while the London sporting event is televised.
With Mo Farah and Usain Bolt competing in the championships at the Olympic Stadium in Stratford, the company has put a moratorium on cable diversion work during the event, which runs from Friday, August 4 until Sunday, August 13.
And that means Norfolk County Council says there is no point closing Holt Road until those cables can be moved – which will mean disruption could continue into September, which the council had hoped to avoid as school runs will have started again.
John Birchall, public liaison officer for the NDR, said: 'Until the BT cables are diverted over a new bridge, we are going to have to keep Holt Road open.
'It's the cables which are the limiting factor.
'We had an unexpected discovery that at the time we wanted the work to be done they have a moratorium on moving fibre optic cables because of the World Athletic Championships. So we have got to wait until the middle of August.
'We would like to have got as much as we could done during the summer holidays, because when it closes there will be extra pressure on Reepham, Horsford and Drayton and now it's going to run into September.
'It's not ideal, but this is something we were not aware of until very recently.'
When Holt Road does shut, traffic will be re-routed along the realigned New Drayton Lane to Reepham Road, until the NDR opens and provides a route back to the A140 Cromer Road.
A BT Openreach spokesman said the company was willing to be 'flexible' should the council wish for the work to go ahead on a different date.
But Mr Birchall said the council had been told the earliest date was only after the championships had finished.
It is now likely to go ahead between August 14 to August 26.
The BT spokesman added: 'Naturally, we always try to avoid disruption when major events are being held and customers are using our network to watch the event via TV or streaming on the internet.'
The next phase of work
The next phase of work on the Norwich Northern Distributor Road will see two-way traffic lights on a Spixworth Road from next week.
The lights, in Buxton Road, will be put in place after the morning peak on Monday and will be in place for two weeks, to allow for the diversion of a gas main. Also starting on Monday is a week of overnight closures on the B1150 North Walsham Road, to allow the final surfacing and tie-in of the NDR roundabout - a week later than originally planned.
The road will close at 8pm each night and open no later than 6am the following morning. The aim is to complete the work in five nights.
The two-week closure of Buxton Road originally due next week has been postponed so as not to clash with overnight closures on North Walsham Road.
And Holly Lane, due to close for good on Friday, will remain open until Friday, July 21
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