Speed versus yellow signal condition

[Robert2d6]

I have a question regarding a yellow signal. If the speed limit on the section of track is 60 mph, and you encounter a yellow signal, what should the recommended speed be after passing that yellow?

 

[JackDownUnder]

Here is an excerpt form a previous thread
The speed is determined by a "Lookahead" - if the AI passes an amber signal, it will proceed at half the speed limit. If it sees a red ahead, the AI will slow down to stop before it.

I think that there is a little bit more to it than the above?

 

[Scottbe8]

If an AI train approaches a signal that is neither GREEN nor RED, it will slow down to one of the speeds listed below. If there is a RED signal within 1 km of the train, it will slow to that speed. If there is a RED signal within 0.1 km of the train, it will apply its brakes and crawl forward to .01 km in front of the signal.

IF the speed limit is 35 km/h or less, the train will continue at the speed limit.
IF the speed limit is greater than 35 km/h but less than 70 km/h, the train will slow to 35 km/h.
IF the speed limit is 70 km/h or greater, the train will slow to half the speed limit.

 

[sniper297]

In the US it depends on the railroad, altho most have similar rules. To make it more complicated, the standard US color light signals built into Trainz don't use all the aspects. Using BNSF for an example;

Green = clear, whatever the max track speed is.
Flashing yellow = Approach Medium - proceed prepared to pass next signal not exceeding 40 mph.
Yellow = Approach - Proceed prepared to stop at next signal, trains exceeding 40mph immediately reduce to 40mph.
Flashing red = restricting, proceed at restricted speed (20mph or 15mph depending on what the local restricted speed is).
Red - Stop.

 

[itareus]

I have a question regarding a yellow signal. If the speed limit on the section of track is 60 mph, and you encounter a yellow signal, what should the recommended speed be after passing that yellow?

In the real world, a yellow signal is a warning that the next signal may be be red (but of course the next signal may be another yellow or even a green). It is up to the driver to drive at a speed, within line speed, that allows him or her to stop safely at the next signal should that be red. Exactly what that speed is will depend on a large number of variable factors e.g. line speed, train speed, loco/train weight and braking efficiency, distance to the next signal, sighting distance to signal... etc.

Trainz AI, as others have pointed out, uses a compromise and slows to half line speed on yellow, sensible if the signals are a short distance apart but not if they are 5 miles apart !

 

[Robert2d6]

Thanks for all the responses. I have had a problem running the South China passenger route on the last station, having a yellow, immediately followed by a red. The brakes on this train are not the best, but I think that I have not been slowing enough on the yellow to be able to stop before running the red signal. I will try the info I have read here and see what happens.

 

[Dermmy]

Two signals too close will always be a problem for the AI. If the second sig is red SDADs will be the normal outcome. The fix is to either get the AI slowed down enough before the first sig, or change things on the route. Trying

-autopilotsignaldistance=

in trainzoptions.txt might help. This tag defines (in meters) how far ahead the AI starts to react to signals. IIRC Default is either 200 or 500, but 1200 or even higher is a more practical value. The higher value shoud have the train slowed down enough at the Yellow that there is a chance of it stopping at the Red...