Here is the full list of all 47 Pixel Traffic: Highway Racing achievements.
Unlock all cars
Unlock Super Mini car
Unlock Green Super Mini car
Unlock Cruiser Plus car
Unlock Racing Plus car
Unlock Racing car
Unlock Muscle Tuning car
Unlock Super Mini Sport car
Unlock Offroad Supercharged car
Unlock Offroad car
Unlock Offroad Tuning car
Unlock Mini Sport car
Unlock Pink Cruiser car
Unlock Cruiser car
Unlock Mini Sport Tuning car
Unlock Police car
Unlock Mini car
Unlock Pink Mini car
Unlock Tank
Unlock Battle Tank
Unlock Heavy Tank
Unlock Muscle Super car
Unlock Muscle car
Unlock Racing Supercharged car
Save 1000 coins
Score 300 points
Score 250 points
Drive over 150 km/h for 3 seconds
Drive over 200 km/h for 3 seconds
Drive over 250 km/h for 3 seconds
Drive over 300 km/h for 3 seconds
Drive over 320 km/h for 3 seconds
Drive over 100 km/h for 3 seconds
Save 500 coins
Save 300 coins
Save 200 coins
Score 200 points
Save 100 coins
Score 150 points
Unlock Coupe Tuning car
Unlock Coupe Plus car
Score 100 points
Save 50 coins
Score 50 points
Crash your car
Score 25 points