"modern control systems make it difficult to throw a switch immediately in front of or under a train"
The old mechanical interlocking plants installed way back in the 1920's and 1930's would not allow you to quickly change a route through an interlocking after it was set and "clear" signals where displayed for a train to enter and pass through.
There was a forced delay involved. You could change a route through the interlocking, but you had to set it to display stop signals on the selected through route and then wait several minutes (depending on the interlocking design) before it would allow a change of route.
And the interlocking machine (part mechanical / part electrical) would not allow any route changes on "running" tracks that where occupied. You could route a "station" track that was occupied by a standing train to an unoccupied "running" track to get the train out of the station, but the standing train would see a stop signal until the route was completed to an unoccupied "running" track.
And that was without computers....
The old mechanical interlocking plants installed way back in the 1920's and 1930's would not allow you to quickly change a route through an interlocking after it was set and "clear" signals where displayed for a train to enter and pass through.
There was a forced delay involved. You could change a route through the interlocking, but you had to set it to display stop signals on the selected through route and then wait several minutes (depending on the interlocking design) before it would allow a change of route.
And the interlocking machine (part mechanical / part electrical) would not allow any route changes on "running" tracks that where occupied. You could route a "station" track that was occupied by a standing train to an unoccupied "running" track to get the train out of the station, but the standing train would see a stop signal until the route was completed to an unoccupied "running" track.
And that was without computers....