Understanding the Efficacy of Median Barrier Scuppers on Wildlife Passage

Focus Area

Wildlife & Ecosystems


Natural Resources






2-3 years

Research Idea Scope

The efficacy of scuppers or cutouts in ‘Jersey’ or concrete median barriers on passing wildlife remains untested; yet DOTs utilize scuppers as mitigation for the impacts of constructing concrete median barriers along the nation’s highways (Clevenger and Kociolek 2006; 2013). The goals of this project are to determine if (1) animal species utilize scuppers placed within concrete median barriers; (2) what guilds of animals, if any, can successfully utilize scuppers; (3) understanding the minimum size of scupper required to facilitate safe wildlife passage, if applicable; and (4) determining how frequently scuppers become clogged or blocked with vegetation/roadside debris to document potential decreases in the efficacy of scuppers. If wildlife species do use scuppers, it will be important to understand the minimum scupper size and spacing at which passage occurs. Standard design criteria on this topic are also lacking. If scuppers are not effective at passing even the smallest of wildlife, DOTs could redirect their efforts at developing more effective mitigation strategies that minimize wildlife-vehicle conflicts. An additional component of this research might include assessing the effects of thrie-beam barrier (and barriers thought to be more permeable to wildlife) on wildlife movement. The study design on this research will be key. Ideally a few disperser types or species would be studied. Potential study designs could include roadkill surveys or camera trapping using paired or multiple comparisons within the same habitat type(s) (e.g., median barrier with no scuppers vs. median barrier with scuppers vs. no median barrier). This work would likely include the placement of camera traps/infrared sensors above scuppers on median barriers at several study locations and the simultaneous collection of roadkill data and information on habitat quality. A power analysis should be conducted to ensure an appropriate study design is selected and the number of animal detections is maximized. References: Clevenger A.P. and A.V. Kociolek. 2013. Potential impacts of highway median barriers on wildlife: State of the practice and gap analysis. Environmental Management. 52(5): 1299-1312. Clevenger A.P. and A.V. Kociolek. 2006. Highway median impacts on wildlife movement and mortality: State of the practice survey and gap analysis. Prepared for the California Department of Transportation, Sacramento, California.

Urgency and Payoff

This research could be applied immediately nationwide. Caltrans’ standard plans include standard designs for median barrier gaps or scuppers. The development of standard or revised plans could continue or cease depending on the results of this research.

Suggested By

Lindsay Vivian Caltrans (916) 653-8566

[email protected]