In North America slide fences are typically connected in such a way as to shunt the track circuit when activated. This causes signals on either side of the slide fence to display a restricting indication, requiring trains to travel at a speed enabling them to stop within one-half the range of vision. On lines formerly operated by the Pennsylvania Railroad, signals connected to a slide detector have an 'SP' placard, reminding engineers to watch for slides when governed by any restrictive speed signal.
