PLANS to build a tunnel under the M4 as part of the Wichelstowe development have been described as madness by councillors who believe alternative routes need to be considered.

Coun Wayne Crabbe (Con, Wroughton and Wichelstowe) says he wants planners, residents and councillors to consider placing a bridge over the railway as a way of easing traffic rather than digging under the motorway.

On Tuesday it was decided to alter the road layout of the 4,500-home project at the planning committee but this will still mean a tunnel going under the motorway as a key exit from the development.

At the meeting, members of both Labour and Conservative parties raised concerns about the viability of building the project which they believe could cost up to £50m.

While they could not vote on the issue at the time, they resolved to look at the tunnel in more detail at a later date.

Coun Crabbe said: “It’s absolutely mad that they’ve even considered this. I’m not sure if they were smoking something at the time but it is just not a sensible option.

“We are talking about tunnelling under effectively 10 lanes of the motorway on land which is constantly wet regardless of the weather because of its location.

“It could end up costing something close to £100m by the time you consider construction costs and the cost of constantly pumping out water to prevent it from flooding.”

Without the tunnel it would leave the exit either via Wharf Road or Croft Road, which Coun Crabbe believes would lead to chaos when combined with the traffic going to Nationwide on Pipers Way.

He said: “There needs to be another exit. We were told at the planning meeting that we don’t need to deal with the issue of the tunnel for another 10 years.

“I think it’s something which needs to be addressed as soon as possible and not just left. A bridge over the railway seems the best option. It means people have a direct route into Swindon without having to go down to junction 16 of the M4.

“Costing would be much cheaper I imagine and while working around rail tracks is difficult there are those in the profession who have the knowledge and expertise to carry it out.”

However, a previous council report has said the best option remains exiting the development by the M4.

A council spokesman said: “This issue has been thoroughly examined and an independent review by various experts concluded that the best access route into and out of the site – whether that is by tunnel or bridge – is under or across the M4.

“The revised Wichelstowe masterplan that was approved by the planning committee on Tuesday night fixes a long-term date for when the new access route needs to be built, because more than 2,500 homes need to be completed on the site before the access is required.

“This makes the final decision on the access solution between seven to eight years away, and further consultation will be undertaken with the public nearer the time.”