Here is the full list of all 40 Roundabout achievements.
Honk your horn 500 times, then honk your horn 500 more.
In "Run Like Crazy", get 150 yards away.
In "Destruction Derby", take out 8 cars.
In "Death from Above", survive for 30 seconds.
Die 360 times.
Drove straight for Beth.
Reach 100% completion on a mission.
Unlocked the Reverser Wheel.
Unlocked the Pickup Finder.
Make a huge mistake.
Aggressively warn a dozen pedestrians with the Trafffic Coner.
Stand still for a minute of silence at The Memorial.
Unlocked the Inflatiboat For Cars.
Unlocked the Traffic Coner.
Purchase a pet eagle.
Purchase something from The Chrome Dome.
In "Ball Bouncers", bounce the ball at least 12 times.
Follow a lady into the big smoke.
Collect every star in a single ride.
Purchase some property.
View the "How's Your Driving" screen outside of the DMV ride. Useful, isn't it?
Unlocked the Multiplier Freezer.
Unlocked the Beary Nice Music Box.
Survive the Mountain Fair Demolition Derby without exploding.
Revolve over 53,596 times.
Complete your first eSports Speedrun Challenge.
Get a better eSports Speedrun Time than the No Goblin team.
In "Limocide", take out 50 pedestrians.
In "Farming Simulator 1977", complete your farming in under 40 seconds.
In "The Great Hunt", find 6 regions.
Reach a 35x multiplier.
Collect every Cash Stash.
Accomplish every Sick Jump.
Discover all of the horns.
Purchase every hat and paint job.
Collect every star in every ride.
Purchase every property.
Reach 100% completion for the entire game.
Complete an eSports Speedrun without exploding.
Drive the entire "classic" length of Desert Limo without crashing.