When you click Join on an activity tile you will be on the loading (Info) screen. A card will appear for each Power-Up available in that activity. The card will show the following information: Name of the Power Up, an icon that will appear in the Power Up Holding Bar when in game, the configuration of the power-up (a set quantity, random, road), the duration, quantity, cooldown time, and a description of the power-up. You may need to scroll down to see them all.
If you are already in a map or activity, press the ESC key to go back to the Info screen to see the power-ups. Press the "Return to Ride" button or the ESC key on your keyboard to resume the activity. To find out more about all Power-Ups in game please search for Power- Ups in the FAQS.
COMING SOON! When you enter an activity, and there are power-ups, any power-up cards for that activity will pop up on screen during warm up so you can read them. Also, when a player acquires a road power-up, the power-up card will appear for several seconds informing the player what the function is.