Forza Horizon 3

As you build up fan points you will get the opportunity to compete in "Street Races". Street races are unsanctioned events that happen on roads with regular traffic. You will start seeing them about he time that you create your second event venue (if you have been accepting offered opportunities for head-to-head races). They will be marked on the map by square blue signs with the pointed edges of the square at each for the four cardinal compass points (N, S, E, W - or Up, Down, Left, Right if you prefer). The signs will have two vertical arrows, one pointing up and one down.

Sanctioned races will center around the new venue while the unsanctioned street races are initially near the first Horizon festival at Byron Bay. As you get more racing experience, and specifically, finish more head-to-head races, more street races will unlock and eventually, more will start to open up further out from Byron Bay.

Just win any street race to get this achievement.