Slide fencing
Sometimes we install slide fencing alongside tracks. These electric fences send a warning signal if touched or broken by an obstacle. Find out how they work.
Slide fences: how they work
What are they?
Sometimes we install slide fences along our tracks—perhaps you’ve noticed them. They consist of rows of electric wires and are designed to warn train drivers of potential obstacles—typically rocks or branches—on or near the tracks.
Two types of slide fencing
- vertical slide fences: These are installed along the tracks on wooden or metal poles
- horizontal slide fences: These are mounted above the tracks on a metal framework
Sometimes you’ll see both types of fencing on sections of our network, especially in steep, mountainous regions.
How do they work?
When the slide fence is hit or broken by falling debris, it triggers a signal detected by track-side or TGV onboard signalling systems. These then alert approaching train drivers to stop the train. In railway jargon, we call this a “slide fence activation”.
The slide fence also triggers an alarm at the switching station responsible for signalling in the sector. Drivers then apply a standard procedure designed to enable traffic to resume as soon as possible in the area concerned.
The safety procedure
The nearest train moves in to “investigate”
When an obstacle hits a slide fence, traffic is immediately suspended. To assess the situation, the nearest train is dispatched on a fact-finding mission. It travels at low speed to the area protected by the slide fencing, and the driver reports back:
- is the obstacle(s) on or near the track?
- can the driver remove them or does a maintenance team need to be called in?
- is any of the infrastructure—slide fences, tracks, or other equipment—damaged?
Next steps
With this information, we can decide if traffic can resume safely in the sector, or if repairs are needed. In the latter case, specialized SNCF teams are dispatched to the site.
How does this affect rail traffic?
Two possible outcomes
Traffic resumes gradually, but at lower speeds:
- if the obstacle is far from the track
- if the driver can clear the track
Traffic is suspended:
- if the obstacle is too heavy to be removed by the driver, or if it has damaged the slide fence’s tensioned wires. That’s when we call in specialized crews to clear the track and maintenance teams to repair the wires.
- if rail assets are damaged. In that case, specialized teams carry out the repairs—sometimes these are temporary fixes to avoid lengthy traffic disruptions, and the teams return at nighttime to complete permanent repairs.
Regular maintenance
Our track agents, and specialized electric crews conduct regular maintenance operations and inspection rounds to remove any obstacles and keep slide fences in good working order.