Motorists have been warned to expect three months of “mayhem” when Cornwall Council trials major changes to traffic flow in part of Helston.

The authority is attempting to find a solution to traffic complaints in Cross Street, where residents have experienced years of misery over the speed and amount of cars using the road as a “rat run.”

However, there are fears that the proposed changes will simply have a knock-on effect in other parts of the town.

In the trial, traffic travelling over St John’s Bridge from Cross Street, towards the main road, will no longer be able to turn right onto Penzance Road. Instead, cars will be forced to turn left and go around the Porthleven roundabout to double back on themselves, if they wish to head to Penzance or Hayle – or take a different route through the town.

At the same time, cars travelling down Sithney Common Hill from the Penzance direction towards Helston will be stopped from turning left onto St John’s Bridge.

No fixed date has been given for when the changes will come into force, although it is understood to be "this spring."

During the three-month trial period there will be traffic monitoring both in Cross Street and in other parts of the town, such as Church Street and the town centre, to identify which routes vehicles are taking instead.

Announcing the plans to Helston Town Council on Thursday, Cornwall councillor Judith Haycock said: “It can’t be [trialled] just for a month, because people will just put up with it.

“After a month people think, ‘I’m not going to do this, I’ll do something else’ – and we want to know what that ‘something else’ is before we do an expensive job and find out it hasn’t made the problem better for Cross Street, but has made the problem worse for St John’s, for example.”

Town councillor Rev Danny Reed feared it could result in “horrendous” traffic in Church Street, adding: “There will be a huge back up, which will cause mayhem in Church Street, Meneage Street and Wendron Street.”

Mrs Haycock said “ideally” traffic would go around the town completely, but conceded that Cornwall Council “doubt very much” that some vehicles would.

She had already warned officers not to try anything around Flora Day, she added.

Town councillor Mike Thomas described the ideas as “crazy,” adding: “This is an absolutely outrageous decision.”

He believed the “real problem” was traffic coming from Redruth road and using Cross Street as a cut through, and said “they won’t be deterred by that.”

Despite admitting he “detests” speed humps, Mr Thomas said in his opinion these, coupled with a 20mph speed limit in Cross Street, was all that was needed to resolve the problems.

However, Mrs Haycock said traffic monitoring already carried out in Cross Street showed that 90 per cent of vehicles actually came from within Helston and that the majority did not speed along there.

She added: “This has been debated for the last 20 years since I’ve been a councillor. Cornwall Council has been accused of doing nothing. This is the only possibility that anyone has come up with, so we will trial it.”

Her fellow Cornwall councillor Phil Martin agreed: “We have got to try something” and pointed out that this was only a trial, not a full traffic order.

He also described speed limits as “like padlocks – they’re only for honest people” without any enforcement.