The scenarios might seem a bit daunting but dont worry they are actually quite simple. Follow the markers and BEWARE RED SIGNALS. Passing a signal at danger will cause a fail of the scenario.
I went over the speed limit and at times crawled into the station slowly to avoid the red signal. Neither failed the scenarios.
Take your time and if lost pause the game to see objectives. Dont worry about getting to your station or destination on timr. Being late is not a fail.
Thanks to SmactSilly:
Scenario 4 gets a little tricky since you have to manually switch the tracks during the refueling portion of the scenario. It doesn't tell you that you have to do this or show you where to do it, but it is easy enough to find the manual switches on the tracks if you look around.