Highway median barriers are used to separate lanes of traffic and enhance motorist safety on freeways and multi-lane interstate highways. Median barriers of all types have the potential to impede animal movements across highways. Barriers also can increase the risk of motor vehicle accidents by causing wildlife to become trapped or confused while on the road searching for a place to cross. A recent Transportation Research Board report highlighted the need to better understand the potential impacts of highway barriers. The lack of information to properly assess environmental impacts is causing significant project delays and increasing transportation project costs. This study will collect, review and synthesize literature on highway median barriers, their impacts to wildlife movement and performance of mitigative design solutions and provide Caltrans with sound, scientifically defensible information for completing median barrier projects.