Individual study: Comparing the effectiveness of earthen escape ramps with one-way gates in Utah
Bissonette J. & Hammer M. (2000) Comparing the effectiveness of earthen escape ramps with one-way gates in Utah. USGS Utah cooperative Fish and Wildlife Research Unit, Logan, Utah report.
This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.
Install one-way gates or other structures to allow wildlife to leave roadways
A replicated, controlled, before-and-after study in 1997–1999 along two highways in Utah, USA (Bissonette & Hammer 2000) found that earth escape ramps reduced road mortalities and were used more often than one-way escape gates to enable deer to escape highways with 2.4-m-high barrier fencing. Road mortalities decreased more after ramp installations at two sites (after: 4.8 and 2.0 killed/km; before: 6.7 and 4.6 killed/km) than at a control site during this time (after: 4.0 killed/km; before: 5.2 killed/km). At one site, 188 successful ramp crossings were recorded. At the other, 192 were recorded. Combined values from both sites showed ramps were used 8–11 times more often than were one-way gates. Nine earth ramps (1.5-m drop-off) were installed along 2.4 km of highway in 1997 and seven along 2.4 km of another highway in 1998. Ten and eight one-way gates respectively were installed previously at these sites (installation date not stated). Animal movements across ramps and through gates were monitored from May–July until October in 1998 and 1999 using track plots. Road mortality and monthly spotlight counts of deer were carried out before and after construction of ramps along both sections, and along an 8-km control section (1-m fencing, no mitigation measures) in 1997–1999. Cost-benefit analysis was also carried out (see original article for results).
(Summarised by Rebecca K. Smith)