Here is the full list of all 15 Paper Train Traffic achievements.
Accumulate 50 or more stars
Complete the tenth level
Accumulate 10 or more stars
Complete the first level
Reach and travel through the forest
Reach the castle on the high cliffs
Witness the train falling into the depths
Reach and load up on goods in the harbour
Reach the quarry and load up on cargo
Reach the vast cloudy mountains
Accumulate 100 or more stars
Accumulate 150 or more stars
Accumulate 250 or more stars
Accumulate 350 or more stars
Accumulate 500 or more stars