@douglas sorry but the number of trains does make a difference! It shortens the wait time on station. Total travel time includes waiting time on a station.
Let’s take the worst example: 30 km line, 1 train, an Oil canister arrived on a station right after the train left.
Train takes 10 minutes to reach the Oil Refinery. How long Oil canister will wait for the train to return? 20 minutes! Plus 10 minutes for the trip, Total travel time – 30 minutes. Not good at all.
Now let’s add a second train: Oil canister will wait 10 minutes. Plus 10 minutes to reach the Refinery -> almost there!
Now let’s add 2 more trains: the closest returning train is only 5 minutes away! Total travel time – 15 minutes.
Problem solved.
So frequency directly impacts total travel time. I’m not guessing, I’m doing this in the game.
BTW we’re not discussing our points of view here, someone has a problem of creating a long line with long trains. And I just gave a solution. If you don’t believe it, just try it! I swear no cheats or magic tricks.