Reply to "Runaway engines - Limiting the top speed"

It's not that simple either Dale.  The tach reader is not active when the engine is stopped.  And, the only way to know the engine is not stopped is by looking at the tach reader output!  The motors may draw considerable current before the engine starts moving, depending on the load and grade.  Remember, this has to work in the most extreme situation, say 35 cars going up a 3.5% grade, etc.