Can be done in Sandbox mode by driving in a circle or placing a circuit of decorations and connecting them in a loop.
Using the Deco Plaza decoration I made donuts around the circle thing in the centre of the plaza. I was able automate this by tying string to hold left
and then propping the controller with a heavy book weighing down
.
I was able to estimate the top speed of the buggy at 35 kmph. Meaning the minimum time to get this achievement on its own is about 42 minutes.