Autumn is one of the main times of the year when adhesion becomes a problem. As leaves and rain fall onto the tracks, passing trains compact them into a thin, slippery layer that dramatically reduces grip—much like black ice on a road.  It is a problem familiar to operators the world over.

Adhérence is an in-house project that includes experts in rail traffic, network maintenance, driving and rolling stock. Together, they’re working to improve our response to the two major issues caused by low wheel-to-rail adhesion: wheel spin and wheel slide.

Wheel spin is a lack of adhesion when the train accelerates. When wheels can’t grip the track, they spin, making it hard for drivers to accelerate and run at normal speeds. This can delay your train or even reduce it to a standstill. When that happens, traffic grinds to a halt until a locomotive arrives to assist the disabled train.

Poor adhesion also makes braking distances longer. In the worst cases, the wheel locks and slides along the track, causing enough damage to both wheels and track to require maintenance.

Today’s rolling stock is designed with fewer wheels, reducing points of contact with the rails. That means that each axle has to work harder during braking and acceleration—but if they apply too much force, the wheels may slip or lock. Wheel slide protection software aboard our trains can limit slippage during braking, much like the ABS system on a car. Together, these 2 measures help limit wheel profile damage and reduce maintenance time. As always, the aim is to avoid cancelling trains and deliver safe, comfortable, on-time service for our customers.

To keep leaves and other plant debris to a minimum, we start pruning and clearing brush in the spring, focusing on particularly vulnerable high-risk areas.

Leaf-busting trains take priority over other traffic, clearing the rails of debris and significantly reducing the risk of losing wheel-to-rail adhesion. The tools we use:

• The Sleet Brush system is a “dry cleaning” method that scrapes off deposits by brushing the rail vigorously with a set of steel blades.
• We also treat and clean nearly 300 metres of track near our Haute-Picardie station in northern France with a light, portable tool adapted from an existing system for clearing plant growth from platforms.

When tracks are coated with slippery leaves, a train can keep moving even if the wheels are locked. Braking time is longer and the rail acts as a plane, leaving flattened areas on the wheel’s profile. These are called wheel flats. When this happens, the train must go to the workshop, where the wheel is machined and restored to its original profile. This operation is carried out in a maintenance pit using a machine tool to smooth out the wheel surface. In the most extreme cases, a full wheel replacement may be necessary. These are major maintenance operations, requiring specialized facilities and extended downtime for the damaged train.

We’re also taking new steps to improve reports by and for our drivers, and we routinely use awareness campaigns to help adjust their driving techniques.

We also work with mobility authorities to develop and deploy a transport plan that protects our rolling stock during high-risk periods. As always, the aim is to keep train delays and cancellations to a minimum.