THE HIGHWAYS Agency was this week forced to place emergency speed restrictions on the M6 in the West Midlands after reports that a section of the road was sinking.
The 50mph restriction on the 15km section between Junctions 3 and 4, which carries 120,000 vehicles a day, comes despite the Agency having spent £3.3M on strengthening works to control expected subsidence from recent mining works underneath.
Between December 2000 and July 2001 a 300m long, 4m deep shaft was drilled 900m beneath the road surface by mining firm RJB Mining, which had agreed to fund the road strengthening.
Strengthening work to a 1.2km section between Junction 3 and Corley Services was completed in August by contractor Birse working with the Agency's agent WS Atkins.
A 750m long precast reinforced concrete slab was placed under the carriageway. It was designed to ensure that the road - expected to sink by 2m over six months - sank evenly.
By last week the road had dropped 1.2m as planned, but undulations in the surface have forced the Agency to reduce the speed limit.
INFOPLUS www. highways. gov. uk