As they make their way along the ACO guide system, animals are guided under access roads without hindrance thanks to the use of stop channels. Animals often stray onto the asphalt surfaces of side roads in the direction of the main carriageway. The gratings, designed specifically for amphibians, act as a trap: animals pass through the openings into the channel body below, able to continue on their way to the nearest tunnel crossing.
Specially designed gratings with differing mesh widths have to perform several functions at once: amphibians must be allowed to drop safely through the large openings into the channel body, pedestrians must be able to walk over the stop channel without injury thanks to the narrower mesh widths in the central area, and heavy goods vehicles must be able to drive over the stop channel without risk of damage. Highly resilient, durable cast iron provides the ideal solution.