Retro Highway (UP)

Locations are unlocked by completing in-game challenges. You will always have three active challenges that you can complete per run.

If you're having trouble with a challenge you can skip one every 15 minutes. Because the challenges get harder and harder I tried to only skip a few that seemed really hard for me so I didn't get stuck with only hard challenges at the end.

Some clarifications for somewhat unclear challenges:

Puddles are only on the ice level. I thought those were patches of ice considering there is a blizzard going on but they are puddles. EDIT:C64 Mat says that the oil slicks on the desert level count as well. Thanks!

A Near Miss is when you are about to hit something (a vehicle or an obstacle) but you swerve out of the way and a Close Call is when you just ride straight next to a vehicle.

For the Do no stunts for x meters challenges, Near Miss and Close Call both count as "stunts" so you have to really avoid everything. I recommend the first level due to lower vehicle density.

For the Don't collect coins for x meters challenges, Near Miss and Close Call award coins but do not count against this challenge, you just need to avoid the coins you can see directly.

The downtown level and the desert level have the traffic cones that you can knock over. In the downtown level it is specifically the cones near the construction workers but not the divider posts that are sometimes between lanes of traffic. In the desert level they are in the divider and are more plentiful at a time - I recommend using the desert level to tackle these challenges.