For anyone else interested in the trackside signage of Victorian railways. What got me looking was learning about coast boards. Seems to be instructions to the driver on what to set the train’s power output.
The original documentation of these coast boards indicate that they were put up because of power efficiency concerns, but I wonder if they were also used for speed control. The Tait trains didn’t have speedometers and follow-on searching seems to indicate that other electrical drives use these to control the output of the generator, and thus the train’s acceleration.
links