Forza Horizon 2

There are 150 reward boards in the game and for this you need to just drive through 25 of them.

Reward boards are scattered all over the map and will appear on your map when you drive near their location as either green or red icons.

Heres a screenshot as well as here is a link to a guide http://www.vgfaq.com/forza-horizon-2-reward-boards-locations...

Here's a short video also showing the locations (Something to snap on your One) Credit to VGFAQ