Forza Horizon 2

You will often see vehicles parked along the side of the road, on sidewalks or in plazas/driveways with event markers near them. Drive up to these and accept the event. These are bucket list challenges (as explained by Ben when you first find one, usually the Agera R speed challenge). There are many of these scattered around the game world, but they are usually simple challenges, such as crossing a checkpoint doing over 125mph in a Koenigsegg, reaching a point in a minute and thirty seconds in a McLaren P1, etc.