Script SC34 Approach release signal (by adlet)
This script implements an approach release signal.
Recommended for use with two-lamp signals with red and yellow lamps.
• Use cases:
° Dangerous zone the train has to travel at slow speed.
° Examples: a tight curve, a junction inside a tunnel, etc.
° Or just a mandatory stop (stop sign)
• Base operation:
° Signal normally at Stop, texture Off (can use Red too).
° Signal lights texture Approaching when train within Activate distance.
° You can set Approaching as red if stop expected or yellow if not.
° Approaching will turn to Path Blocked if the train is stopping.
° Train slows down to coast speed when within Slowdown distance.
° At that time the timer countdown starts.
° Signal turns to Pass and texture to Pass when countdown ends.
° Signal turns to Stop and texture to Off six seconds after the train passes.
° If Slowdown distance > Activate distance, Slowdown distance is used for both.
° IMPORTANT: The slowdown is not in the timetable. Give train time to catch up.
• Signal aspects (match AVP railroad signal 2-lamp aspects):
° Off: no train around – eg aspect 0, all lights off
° Path Blocked: signal locked – eg aspect 1, red
° Approaching: train is approaching – eg aspect 1 or 3, red or yellow
° Pass: pass at caution – e.g. aspect 3, yellow
• Signal chain setup
° Several approach release signals can be set one after another, at some distances.
° Set progressively reducing speed limits.
° For all but the last signal, set Approaching aspect to 3 (yellow).
° Set Activate and Slowdown distances longer than distance to the previous signal.
° Signals can activate independently (after the previous signal is Pass) or all together. Link by adding all other signals into the first.
• Timer countdown:
° If it expires after the train arrives at signal, the train will stop.
° Approaching will turn to Path Blocked if the train is stopping.
° If timer expires before, the train will coast through the signal.
° Recommend setting track speed at the last signal to its coast speed maximum.
° Train distance is checked every 6.5 s – there will be lags to Activate and Slowdown
° Train distance is checked every 6.5 s – so signal change to Red and slow-down to "Coast speed" will occur with less distance remaining to the signal. For example, at 40 km/h the train covers almost 80m in 6.5s.
Example: If the train’s initial speed is 40 km/h, the Coast speed" 20 km/h, and the slow down period is at 150m, the train will arrive at the signal in 27s if the signal is checked exactly when the train enters the slow-down area, or sooner if the check is later. Setting the timer countdown to 28s or longer will mean the train will stop at the signal for a few seconds. Setting the countdown to 20s or less will mean the train will slow down to 20 km/h and will coast through the signal.
