Need for Speed: Carbon Message Board  

First you have to find a orange arrow while free roaming, stop and wait for them to stop near you. Then press the enter key and the world map will show up. Press a green flag and race and get there using the GPS (problem is you must drive right through these green thingys or you won't finish).

find a orange arrow while free roaming: This is an enemy crew member.

Press a green flag: These will be the finsih line, if you pick one of them. To do this simply press it as you would for race events. It is best if you are the closest and are facing the right way to the finish line you pick.

and race and get there using the GPS: It will be shown as a blue arrow at the top of the screen like with any GPS.

(problem is you must drive right through these green thingys or you won't finish): You know at the end of each event, there is a wierd green fountain looking thing that you cross to end each event? Well instead of just cossing them, you have to actually cross it while you are between both of them, or you will lose

Every crew challenge is worth 1k. Hope it helps