I'm sorry, but I'm having trouble understanding how to set up the gas stations. Could you please explain it to me or share a save file with gas stations for me to learn from?

Gas stations?

Do you mean fueling stops or do you mean fluid stops for gasses?

‘Starting with 2.3.0, LTN supports a new station type: 'Fuel Station'. Fuel station support must be explicitly enabled by setting the setting.ltn-schedule-fuel-station’,I set up a virtual signal for a gas station at the station, with a network ID and fuel signal, but trains that are out of fuel still don't go to refuel.

Well, trains that are out of fuel can't go anywhere at all.

What you do is you send the signal that it is a fueling station, and then you send a signal for the lower limit of fuel. Like, if you want the train to refuel if it drops below 20 solid fuels, you send "20 solid fuel". (If you are using LTN combinators, make sure the number you send is positive! LTN combinators will try to make the number negative, which won't work.)

This will build an interrupt that says if a train has >= 1 solid fuel and <20 solid fuel, the train will go get refueled. Note that it must have at least 1 of the specified fuel in the train engine inventory.

The interrupt gets built when the train goes to a depot.

And you have to have fuel stations enabled in your game LTN mod settings.

Thank you very much for your answer, it helped me understand how gas stations work. But I want to ask a new question: when a gas station sends a fuel signal, can it only target one vehicle? My train is 2 4, and I set the gas station to send an 80 rocket fuel signal. Even if the vehicle is fully fueled, it still goes to the gas station.