Train Sim World 2

XP grinding method I used
The achievement does pop at Level 20 (350,000AP)

Setup steps
1. Cathcart Circle Line > Explore > Explore on Foot > Neilston Station (Time 08:10)
2. Ignore the Glasgow bound train already there and cross to the other platform.
3. Wait until about 08:15
4. A train will pull up, head to the front of it quickly.
5. When you get to the driver seat, before you take over from the driver. Make a save (Pause then Y).

The Repeating steps
6. Take over from the driver using Y and pressing Begin to instantly earn 4000AP.
7. Quit out to the main menu immediately, you will keep the 4000AP you earned.
8. Press "Resume Savegame" and repeat 6-7 over and over to earn 4000AP fast multiple times.

You can earn about 12000AP a minute using this method on a Series X with the fast loading screens.

Note: if the game refuses to load the save because it is greyed out, quit TSW2 and reboot the game.