Proposals to narrow traffic lanes on a busy Norwich road to squeeze in a new bus route are to go before the public.

Transport officials have developed designs, estimated to cost �920,000, to widen parts of Grapes Hill to help buses travel quicker southbound toward the Chapel Field Road roundabout.

But to create a bus lane while keeping two lanes for general traffic, the plans include reducing the width of the existing southbound lanes from 3.75 metres to three metres.

It is hoped the tighter lanes might prompt motorists to slow down in the 30mph limit, although officials have warned it may prove troublesome for lorries to travel southbound side-by-side.

They added buses will struggle to overtake cyclists safely. The new bus lane will operate 24 hours a day, seven days a week and also allows taxis and cycles to use it.

But the Grapes Hill designs intend to encourage pedal bikes onto a new parallel route from the St Benedicts Street junction into Wellington Lane.

A public consultation on the idea is expected to begin in September, while work to develop the new road layout could start next April.

Norwich city and Norfolk county councillors have welcomed the idea of a new bus lane, which is linked to efforts to speed up bus trips in Dereham Road.

But they have expressed caution about the proposed width of the lanes.

Mervyn Scutter, Norfolk county councillor for Norwich Eaton, told the Norwich Highways Agency Committee: 'It seems to me going from 3.75 metres to three metres is a 20pc reduction. As someone very familiar using that road, I don't feel I have 20pc of spare space going up that road when there's a lot of traffic in it.

'I am broadly in support of the plan but this presents a problem, which I know there's no easy solution but I hope it will highlighted in the consultation.'

Denise Carlo, Green Party Norwich city councillor for Nelson ward, said she supported the plan put forward, as the three-metre bus lane would affect fewer trees than a four-metre bus lane.

She added: 'Slightly reducing the width for vehicles, hopefully that will slightly slow down vehicles. They do tend to rush up to the junction.'

The changes were welcomed as a 'real bonus for bus users' by Bert Bremner, Labour city council cabinet member for transportation.

He added it will make buses more reliable, which should encourage more people to use the services instead of cars.

Joanne Deverick, city council transportation and network manager, told councillors the plan had been 'safety audited'.

She said: 'The three-metre lanes, it's perfectly achievable for a couple of cars to run up the hill together and it might even slow them down.

'Two HGVs - it will be tight. One or the other may have to give way.'

It had been previously thought attempts to speed up bus journey times in Dereham Road and into the city, including the Grapes Hill lane, relied on Chapel Field North being made two-way for buses.

But funding has yet to be secured for the Chapel Field North changes, meaning the Grapes Hill lane will end just short of Chapel Field Road roundabout.

The Grapes Hill project will be funded by central government under the better bus area initiative.