Bat bridges have been included as part of the £42m scheme Enlarge Image

Special bridges to help bats with their flight path have been built as part of a £42m road scheme in Cornwall.

The two so-called "bat bridges" on the Dobwalls bypass are to help the protected creatures use their sonar to find their way to their roosts.

Previously they followed a line of hedges which were removed for the road.

The bridges are to stop them from becoming confused as a result of the hedges' removal and help them continue to fly their usual route.

Bats send out sound and move around following the echo sent back from structures on the ground.

It is important to continually search for better ways to reduce the impact of road schemes on protected species such as bats David Hinde, Highways Agency advisor

The removal of any features which the signals bounce off along routes they frequently use can cause bats to become confused.

Two bridges - costing a total of £250,000 and made out of steel wire and netting stretched in a V-shape - have been built which cut across the bypass carriageways.

They cross along the same path the hedges used to follow.

The Highways Agency will monitor the bridges for five years to monitor their success.

The agency said bats could now follow the structures at a safe height above the traffic.

Highways Agency environmental advisor David Hinde said: "We want to reduce the impact of roads on the environment, so it is important to continually search for better ways to reduce the impact of road schemes on protected species such as bats.

"As this is a relatively new concept, Dobwalls has provided us with a timely opportunity to study how bats may benefit from these types of features.

"The trial will help us to refine our future plans for dealing with changes to habitats on other schemes."

Wildlife measures

Other wildlife protection measures on the bypass include badger and otter tunnels, and a water run for spawning fish.

Work on the bypass started in 2006 and is due to finish in the autumn.

Once it is completed, it should take about 90% of the traffic that uses the A38 through Cornwall away from the village of Dobwalls.

Currently about 21,000 vehicles a day travel through Dobwalls.

The new structures have replaced the hedges that, ecologists believe, bats would follow using echo location to find their way to and from their roosts.