This is a turnout reliability. It pointing out the common problems people have by running trains at prototype speeds through turnouts and the causes beyond dirty track and wheels.
Many model railroader operate their trains at much higher speeds than the prototypes. The reason is found in the roots of unreliable train operation at slow speeds. In other words if you do not want to stall your trains, run it faster. Totally unprototypical. AKA toy train operation.
Why does this work? High speed takes advantage of engines momentum found in the motor armature and flywheels to take the engine through the problem track. But at low speeds, momentum fails.
The most obvious problem is often dirty track and/or wheels. True addressing this can go a long way to improving engine performance. HOWEVER, not all problems are due to dirty track and wheels. This become most obvious when we run trains through Turnouts at low speed..
Turnout Speeds
Having some kind of frame of reference as to the speeds one need to run a train through a given number (#) type turnout can help one understand what one needs to do to safely operate the trains safely. It goes without saying but a safe speed, by definition, also means a reliable speed the train can operate through the turnout without derailing.
In the RMC December 2015 issue, Bruce Chubb wrote an article about signals. Part of the article discussed "Speed Signaling" which means a given signal indicates the safe speed the given train is allowed to proceed at past the signal. At interlockings, this is often directly tied directly to a diverging route through a turnout or series of turnouts. The prototype has speed recommendations for each # type of turnout by number. Below is a table in Bruce's article that compares prototype to model turnout and the recommended speeds for each turnout number.
Why is turnout speed important to know? We want to run trains prototypically.
Why is this a problem? If we assume the track and pickup wheels are clean, running model trains at the correct slow speeds for the given turnout #, you STILL get stalls. Not what we want.
WHY? This is due to electrical failures of point rails and frogs assuming the latter supports a live frog. In other words, parts of the turnout are unable to pass electricity to the locomotive electrical pickup wheels reducing reliable delivery of power to keep the engine going.
SOLUTION: if we want to run prototypical speeds through our model turnouts, one needs to improve the turnouts electrical performance