Fig. 1. The Rauischholzhausen agenda for road ecology: five key questions and potential study designs. There are two study classes, manipulative (m) and nonmanipulative (nm), and three study types: before-after-control-impact (BACI), before-after (BA), and control-impact (CI). Column height indicates inferential strength in ordinal ranks: (1) low, (2) medium, (3) high, and (4) very high. For each design, we provide a qualitative estimate of feasibility in terms of cost, likelihood of required data being available, etc., and a recommendation based on feasibility and inferential strength.