Not 100% sure if I understand your question, but lets give it a shot:
The "quick drive" function loads the route and gives you the list of all the pre-made consists. By default, this list does not seem to have a consist with an engine so its kinda useless and fails the "drive" part of quick drive.
So the other solution to go on a drive if a route does not have a session is to create one yourself. Go to the session page of the route and click "create session" in the top left corner. Now you can just drop all the rolingstock on the tracks the way you like that; you will find them in the bottom tab on the right side of the screen.
Save and start your session and happy "driving without a target".
does quick drive mean just that, explore without and objective?
Yes.
To give "quick drive" actually a driving option, here is what you do:
- Go create a session on any route; which doesnt mather for now.
- Find a nice length of track.
- Again go to that last tab on the right side of the screen.
- Make 1 train the way you like it. Doesnt mather what you put down, as long as it is connected, looks the way you want it and has at least 1 engine it is.
- Now in that tab on the right side, go to the top of it and click "Train mode" (the 2 cars connected to eachother).
- Click on the "get consist" button. Thats the thing looking a bit like a fork at the bottom left corner of that tab.
- Click on that train you just made.
- A "Name" window will pop up. Enter a name suiting the train you just made.
- Press the little "V" button and this train is added to the consist list.
Now you can close this whole thing. Dont saving anything as you wont be use any of it.
Go to a route you like, click "quick drive" and... tada... the train you just made is available to actually drive.
