ENGINEERS working on the A14 Huntingdon viaduct strengthening scheme made an error which prevented double decker buses from passing underneath.

As part of the £7.5million scheme to prolong the life of the bridge, the Highways Agency (HA) has put up 60 signs to highlight the new height restriction, including a number of vehicle-activated warning signs that detect over-height vehicles using Brampton Road.

But the kit used to detect the height of vehicle was set too low, and on Monday the Whippet service going towards Brampton set off the warnings and had to turn around rather than risk hitting the bridge.

The agency yesterday (Tuesday) admitted the sign, installed on Saturday night, was set too low and would need re-installing.

A spokesman said: “The Highways Agency has worked closely with partners including local bus operators to minimise the impact of this work. The design of this scheme has been carefully developed to incorporate a new headroom restriction of 4.4m/14ft 6in, sufficient to accommodate all current scheduled buses that use the route. “Unfortunately the frame for the signage on the bridge was installed slightly too low on Saturday night.

“We have been in touch with the bus company and removed the sign at the earliest opportunity. This will be re-installed at the correct height overnight on Wednesday. We are in discussion with our contractors and local bus companies to avoid a recurrence of such an issue.”

Peter Lee, Whippet Coaches director, said: “A bus set off the alert on Monday. As a caution we turned the bus around. We have worked with the Highways Agency throughout and hopefully this will be sorted out as soon as possible.”