Bat bridge
Introduction A38 Dobwalls Bypass, Cornwall, UK. (2009)A '''bat bridge''' is a structure of varying construction crossing a new or altered road to aid the navigation of bats following the destruction of a hedgerow, and to cause the bats to cross the roadway at a sufficient height to avoid traffic. Bats are thought to follow the lines of hedgerows and woods, and removing these may confuse the bats.The theory is that these "bridges" will be seen by the bats' sonar as linear features sufficiently similar to the old hedgerows as to provide an adequate substitute. The English Highways Agency is performing a study of those on the Dobwalls bypass to determine if this assumption is justified.
Usage ===France ===A89, near Balbigny, Loire, FranceThe first bridge to be installed in France is on the A65 motorway between junctions for Roquefort and Caloy in the Landes department.Two additional bat bridges were completed in November 2012 near Balbigny, on the A89 motorway.=== Germany ===Two metal bridges were built in 2013 to protect the Mouse-eared Bat at Biberach an der Riss, Baden-Wuerttemberg. The structures cost £375,000 (400,000 €).===United Kingdom===Bat bridges have been implemented in the United Kingdom by various agencies, including the Highways Agency, with support of the Bat Conservation Trust.At A38 Dobwalls Bypass, the bridges are more elaborate and sophisticated than the earlier Welsh structures, which consisted of cables strung from poles. +Bat bridges in the United Kingdom Name  Road  Opened  Approx. length Single or dual carriageway  Placement  Approx. cost  Other detailsRef. Stainburn and Great Clifton Bypass  A66  December 2002  Gantry  Single (three-lane carriageway)    High and Low Newton  A590  April 2008  33 m  Dual  In cutting  £45,000 Dobwalls  (2 Structures)  A38  June 2008  Structure 1: 59.47 m, Structure 2: 70 m  Dual  At Grade/In Cutting  £300,000  One structure consists of three steel towers with cables suspended between them carrying mesh panels. The other consists of a single span of cables and mesh panels between concrete and steel anchors either side of a cutting. In the Dobwalls scheme, a third bat-crossing consisted of a raised parapet modification to a new road bridge, Havett Road. Parton to Lillyhall  A595  Dec 2008  34 m  Dual  On embankment  £34,133 Haydon Bridge  A69  April 2009  19.5  Single  In cutting  £60,000 Pwllheli and Criccieth  A497  2006   Single  At Grade   A bat bridge was installed following the upgrade of the A497 to help the six species of bats in the area to cross the road. Elveden  A11 2014   Dual  Various  £350,000  Six bat bridges. Gilwern to Abergavenny  A465  2007   Dual  Embankment   Two bat bridges were constructed during road upgrade in locations where full bridges previously stood. Groeslon  A487  2010   Single    The road runs through the Glynllifon Special Area of Conservation which is home to a lesser horseshoe bat colony. Norwich  A1270  2017   Dual   £1,000,000  Seven bat bridges on the Norwich Northern Distributor Road.
Criticism The overall cost of bat bridges has been criticised in the House of Lords by Lord Marlesford.A team from the University of Leeds examined the effectiveness of bat bridges, gantries and underpasses. They found that one underpass, placed on a commuting route, was used by 96% of bats, but few bats used the other underpasses and gantries, preferring routes which put them in the path of traffic.
See also *Squirrel bridge*Wildlife crossing
References
External links * Roads, Bat Bridges and Gantries: A position statement from Bat Conservation Trust