This description of this achievement should be clear enough. When the game comes to an end you will need to have scored more points than your opponent(s) while not connecting your network of railways to any of the neighbouring countries.
A few tips I can give is to make sure you start with destination tickets on the eastern and southern parts of the country.
Avoid picking destination tickets that have a country as a destination at all cost! The ones I drew at the start of my achievement-winning game were:
- Lugano to Chur
- Zurich to Drusio
During my game, I also drew another ticket connecting the cities of Schaffhausen and St. Gallen, and unfortunately also a ticket to connect a country with. I finished the third destination ticket and decided to accept the deduction for not finishing the last route.
Make sure you will be the player with the longest continuous railway, as this will give you a nice bonus at the end of the game.
In my achievement-winning game I scored 94 points, which was more than my opponent Marg Loughbot's 62 points. This achievement is not very difficult, but if you need some visual aid this is how my achievement-winning game looked like during the final score count:
* if for some reason the image is not present in this solution, just let me know, I can re-upload it! :)