Bat bridge

Bat bridge on the 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.[1] The English Highways Agency is performing a study of those on the Dobwalls bypass to determine if this assumption is justified.[when?][citation needed]

Usage

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.[2]

Two additional bat bridges were completed in November 2012 near Balbigny, on the A89 motorway.[3][4]

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 €).[5]

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.[6]

At A38 Dobwalls Bypass, the bridges are more elaborate and sophisticated than the earlier Welsh structures, which consisted of cables strung from poles.[7][8]

Bat bridges in the United Kingdom
Name Road Opened Approx. length Single or dual carriageway Placement Approx. cost Other details Ref.
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. [7][8]
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. [9]
Elveden A11 2014 Dual Various £350,000 Six bat bridges. [6][10]
Gilwern to Abergavenny A465 2007 Dual Embankment Two bat bridges were constructed during road upgrade in locations where full bridges previously stood. [11]
Groeslon A487 2010 Single The road runs through the Glynllifon Special Area of Conservation which is home to a lesser horseshoe bat colony. [12]
Norwich A1270 2017 Dual £1,000,000 Seven bat bridges on the Norwich Northern Distributor Road. [13][14]

Criticism

The overall cost of bat bridges was criticised by Lord Marlesford in the House of Lords in 2011, for being funded "at a time when we're having to cut a lot of public spending".[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.
  2. ^ Un couloir à chauves-souris, Sud-Ouest, février 2012
  3. ^ Reportage de France 3
  4. ^ Photographies de l'installation des ouvrages
  5. ^ "Warum fliegen die nicht einfach drüber?" (Print version). Kölner Stadt-Anzeiger. 2013-11-02. Archived from the original on 2013-11-06. Retrieved 2 April 2015. Rund 400 000 Euro wurden dafür ausgegeben [Around 400,000 euros were spent on it]
  6. ^ a b "A11 Elveden bypass to be shut for bat bridges". BBC News. 2014-08-04. Retrieved 2015-04-02.
  7. ^ a b "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.
  8. ^ a b "House of Lords Written Answers 10 November 2009: Bats". United Kingdom Parliament. Retrieved 5 June 2011.
  9. ^ "UK | Wales | North West Wales | 'Green' road helps bats to cross". BBC News. 2006-05-02. Retrieved 2009-09-12.
  10. ^ "Bats reject 'safe way' bridges over Norfolk - Suffolk dual carriageway". BBC News. 22 October 2015. Retrieved 27 January 2020.
  11. ^ 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.[dead link‍]
  12. ^ "Road closure for new aerial bat crossing". BBC News. 30 January 2010. Retrieved 5 June 2011.
  13. ^ "Norwich NDR bat bridges 'are not working'". BBC News. 26 Jan 2020. Retrieved 26 Jan 2020.
  14. ^ "Detailed section plan of the NDR" (PDF). Norfolk County Council. 21 Apr 2015. Retrieved 11 Dec 2017.
  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.