Do bat gantries and underpasses help bats cross roads safely?

Published source details Berthinussen A. & Altringham J. (2012) Do bat gantries and underpasses help bats cross roads safely?. PLoS ONE, 7, e38775.
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This study is summarised as evidence for the following.

	Action	Category
	Install bat gantries or bat bridges as road/railway crossing structures for bats Action Link
	Install underpasses or culverts as road/railway crossing structures for bats Action Link

Install bat gantries or bat bridges as road/railway crossing structures for bats

A replicated, site comparison study in 2010 at four bat gantries (or bat bridges) on four roads within agricultural areas of northern England, UK (Berthinussen & Altringham 2012) found fewer bats using bat gantries to safely cross roads than crossing below them at traffic height. The number of bats using gantries to safely cross roads was lower (2–24 bats, <1–11% of crossing bats) than the number of bats crossing roads at traffic height below gantries (10–751 bats, 17–84%). The four bat gantries were of a similar design (height 6–9 m, width 2 m) with two or three pairs of wires spanning the road (20–30 m) with plastic spheres attached. All four roads had 2–3 lanes of traffic carrying an average of 12,000–17,000 vehicles/day. At each of four gantries, crossing bats were observed and recorded with bat detectors during 10 x 90-minute surveys at dusk or dawn in June–July 2010. Bats were counted as ‘using’ gantries when flying within 2 m of the wires above traffic height (>5 m above the road).

(Summarised by: Anna Berthinussen)
Install underpasses or culverts as road/railway crossing structures for bats

A replicated study in 2010 at three underpasses below two roads in an agricultural area of Cumbria, UK (Berthinussen & Altringham 2012) found that one of three underpasses had a greater proportion of bats flying through it than crossing over the road above at traffic height. At one underpass (6 m wide x 5 m high x 30 m long) located on an original bat commuting route, 96% of bats (864 of 904) flew through it to cross the road and 4% (32 of 904) flew over the road above at traffic height. At two underpasses (5 m wide x 2.5 m high x 15 m long; 6 m wide x 3 m high x 30 m long), 4% (39 of 1,117) and 31% of bats (11 of 36) flew through them and 67% (751 of 1,117) and 61% (22 of 36) crossed the road above at traffic height. Both underpasses were not located on original bat commuting routes, but attempts had been made to divert bats towards them with planting. The two roads had 2–3 lanes of traffic carrying an average of 12,000–17,000 vehicles/day. At each of three underpasses, crossing bats were observed and recorded with bat detectors during 10 x 90-minute surveys at dusk or dawn in June–July 2010.

(Summarised by: Anna Berthinussen)