I have been watching the story around the rail accident in CA last week. Two trains, a commuter and a freight train, collided head on in the San Fernando Valley. Right out of the gate the proponents of "positive train control" used the event to draw attention to the fact they have been calling for it for over 30 years. Response from railroad officials, "the systems are not yet reliable"..
I had to laugh a little. We have systems that land wide body jets at airports around the globe automatically, in six degree's of freedom, long, lat and rotation – in wind and weather with zero visibility. But, apparently – if you believe these guys we "don't yet have the technology to control the throttle of a train in 2 degrees of freedom.
Very early on railroads were one of the first adopters' of GPS technology. At first this seems strange; after all I think we can all agree the train is generally "on the tracks" removing a good deal of ambiguity from the problem. Railroads adopted GPS technology early on to control throttle response. The reason being, trains have huge mass and as result, inertia. In order to save fuel costs the railroad figured out that if they optimize when to add throttle before grades they can save huge amounts of fuel.
Think about it.