For full details on the design challenge, read the blog post: http://www.reachingperfection.com/2011/12/design-challenge-racing-towards.html
Basically this is a challenge to design a race map that would be fit for a matchmaking playlist if one were to ever exist. There are thousands of race maps out there, but a good majority of them have framerate issues and do not support splitscreen. They are also too complex or too much of a joy ride. If you think you are up for the challenge then read the post for the full details and how you can get help in perfecting the map before the January 8th deadline.