For this side mission, you'll be required to ride a bike along a specific route.
I highly advise practicing riding a bike before you attempt this, as the controls are a little stiff
Once you have access to the tunnels underneath the ringfort, you can access this mission. The starting line will be on a bridge in between the Farmlands and the Forest regions, just west of the neighborhood of Lillå. You'll be given one minute and 10 seconds to reach the first checkpoint, with more time added one with each passing checkpoint, which should be marked by an icon. There are obstacles in the way, to overcome them, there will be a ramp to get over them. Eventually you will have to make a turn on the main road that leads back to the Archipelago region, the finish line will be a bit beyond the military checkpoint that separates the regions. Once you cross the finish line, you'll then be directed to unlock the container to collect your reward, completing the mission, and unlocking the achievement. It may take a few tries depending on how much you've gotten a hand on the controls, or a bit of luck depending on what machines spawn around you. But with a few tries, it's very doable!
NOTE: As ImCandysKing87 has pointed out, be aware that the markers sometime glitch, and won't appear at all
Edit: Hawkes67 has a Co-op solution:
Get the most competent ' Bike Rider ' to run / ride the course ( He should be fully healed before starting ) ...He then just rides ! Any other members of the group should be at various spots along the course to pick of enemies !
May take a few tries to get it down ... But ALL will get the achievement !
Side note: I had a tank waiting for me at the finish line, fun times!