Here is the full list of all 18 Tiny Traffic achievements.
Solve all puzzles in Chapter 1.
Solve all puzzles in Chapter 2.
Solve all puzzles in Chapter 3.
Solve all puzzles in Chapter 4.
Unlock Chapter 2.
Unlock Chapter 3.
Unlock Chapter 4.
Get to the final level.
Crash your first car.
Crash 15 cars.
Crash 3 or more cars simultaneously
Finish your first car.
Finish 100 cars.
Use a tunnel for the first time.
Use the reset button 42 times.
Crash into a barrier.
Crash into a gate.
Crash two cars into each other, inside a tunnel.