Bat bridge

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.

Bat Bridge on the A38 Dobwalls Bypass, Cornwall, UK. (2009)

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.[1] The Highways Agency is performing a study of those on the Dobwalls bypass to determine if this assumption is justified.

Usage

Bat structures in the UK
Scheme NameRoad NumberRoad OpenedApprox Length of Structure (metres)Single or Dual CarriagewayCutting/Embankment/At GradeApprox Construction Cost of StructureOther details
Stainburn and Great Clifton BypassA66December 2002GantrySingle (three-lane carriageway)
High and Low NewtonA590April 200833 m span between timber supporting postsDualIn cutting£45,000
Dobwalls
(2 Structures)		A38June 2008Structure 1—59.47 m
Structure 2–70 m		DualAt Grade/In Cutting£300,000These bridges are more elaborate and sophisticated than the earlier Welsh structures, which consist of cables strung from poles. At a cost of £250,000,[2] two bat bridges were constructed. One of these, pictured, 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. A third bat-crossing consisted of a raised parapet modification to a new road bridge.[3]
Parton to LillyhallA595Dec 200834 m span between supporting steel structuresDualOn embankment£34,133
Haydon BridgeA69April 200919.5 m between support postsSingleIn cutting£60,000
Pwllheli and CricciethA4972006SingleAt GradeA bat bridge was installed following the upgrade of the A497 to help the six species of bats in the area to cross the road.[4]
ElvedenA112014DualVarious£350,000Six[5] bat bridges.[6]
Gilwern to AbergavennyA4652007DualEmbankmentTwo bat bridges were constructed during road upgrade in locations where full bridges previously stood.[7]
GroeslonA4872010SingleThe road runs through the Glynllifon Special Area of Conservation which is home to a lesser horseshoe bat colony.[8]
NorwichA12702017Dual£1,000,000Seven[9] bat bridges on the Norwich Northern Distributor Road.[10]

France
Bat bridge on the A89, near Balbigny, Loire, France

The first bridge to be installed in France is on the A65 motorway between junctions for Roquefort and Caloy in the Landes department.[11]

Two additional bat bridges were completed in November 2012 near Balbigny, on the A89 motorway.[12][13]

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.[14]

Criticism

The overall cost of bat bridges has been criticised in the House of Lords by Lord Marlesford.[15]

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.[16][17]

See also

References
  1. "New bypass going 'batty' to help the environment". Western Morning News, The Plymouth (UK). April 5, 2008. Retrieved 2009-09-12. Cite journal requires |journal= (help)
  2. "New Bat bridge for bypass : Marishal Thompson Group - Tree Subsidence, Arboriculture, Ecology and Landscape Architecture throughout the UK". Marishalthompson.co.uk. Archived from the original on 2009-11-07. Retrieved 2009-09-12.
  3. "House of Lords Written Answers 10 November 2009: Bats". United Kingdom Parliament. Retrieved 5 June 2011.
  4. "UK | Wales | North West Wales | 'Green' road helps bats to cross". BBC News. 2006-05-02. Retrieved 2009-09-12.
  5. "Bats reject 'safe way' bridges over Norfolk - Suffolk dual carriageway". BBC News. 22 October 2015. Retrieved 27 January 2020.
  6. "A11 Elveden bypass to be shut for bat bridges". BBC News. 2014-08-04. Retrieved 2015-04-02.
  7. Roberts, Geneviève (2007-03-31). "How did the bats cross the road? By using the special 'bat bridge' - Nature, Environment". The Independent. London. Retrieved 2009-09-12.
  8. "Road closure for new aerial bat crossing". BBC News. 30 January 2010. Retrieved 5 June 2011.
  9. "Norwich NDR bat bridges 'are not working'". BBC News. 26 Jan 2020. Retrieved 26 Jan 2020.
  10. "Detailed section plan of the NDR" (PDF). Norfolk County Council. 21 Apr 2015. Retrieved 11 Dec 2017.
  11. Un couloir à chauves-souris, Sud-Ouest, février 2012
  12. Reportage de France 3
  13. Photographies de l'installation des ouvrages
  14. "Warum fliegen die nicht einfach drüber?". Koelner Stadt-Anzeiger. 2013-11-02. Retrieved 2 April 2015.
  15. "Bridges too far? The £500,000 bat crossings".
  16. Berthinussen, Anna; Altringham, John; Fenton, Brock (13 June 2012). "Do Bat Gantries and Underpasses Help Bats Cross Roads Safely?". PLOS ONE. 7 (6): e38775. doi:10.1371/journal.pone.0038775. PMC 3374807. PMID 22719941.
  17. "Bat bridges don't work". University of Leeds. 14 June 2012. Retrieved 15 June 2014.
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