Short detailed guide shows on how to obtain the Museum Line Achievement as the setting in the Europe.
Unlocking the Museum Line Achievement
The Museum line achievement requires you to have all road passenger cars (buses) from the whole timeline on a single line.
So in order to get this achievement you have to start in 1850 and play all the way to 2019, where you'll get the final road passenger car.
Note: This achievement does not require you to buy trams.
An easy way to get this is to built a depot and just buy new road passenger cars as soon as they become available. Once you bought them all, built a simple line and assign the vehicles to unlock this achievement.
Here is the list of vehicles required to unlock this using the european vehicle set: