This special truck straddles...

This special truck straddles concrete blocks and drives at up to 10mph. Underneath is a machine which moves the blocks across one lane. And the great thing is traffic can keep flowing. The barrier is strong enough to stop vehicles crossing into oncoming traffic, but has special joints so it can be moved out of the way swiftly.

"There"s interest in using the system on the M20, M25 and the Aston Expressway in Birmingham, among others," said Chris Sanders, general manager of maker Barrier Systems Inc, based in Rio Vista, California. "Nobody has to take risks picking up cones, and we can move a mile-long barrier in only eight minutes."

In the US, Canada, Italy and New Zealand, the barriers have been used to create variable contraflows at roadworks. That allows as many lanes as possible to be open to cope with peak traffic flows. "It also means we can expand the work area quickly during off-peak hours," added Sanders.

In Britain, the machine would be particularly useful in Kent, where one southbound lane of the M20 is often used to park lorries waiting to cross the English Channel. At the moment it has to be cordoned off by hand, but the new system could do the job faster and without putting workers in jeopardy.