Mortality of amphibians due to roadside ditches has been a matter of concern recently in Japan. Two experiments were done, aimed at prevention of this mortality. A slope attachment improved the chance of the eastern-Japanese common toad, Bufo japonicus formosus, escaping from a roadside ditch. However, since the Japanese brown frog, Rana japonica, escaped by jumping from the ditch, the slope attachment did not change the number of frogs remaining in the ditch. The angle of escape slope on which toadlets could climb was less than 30 degree. Thus, we recommended a shallow V-shaped ditch with an angles of less than 30 degrees for better protection of migrating amphibians.