High Speed Challenge is the fifth and final Challenge Act of Green Hill Act 1 in the console/PC version of Sonic Generations. It is unlocked after clearing every Stage in the classic era and is playable only as Classic Sonic.
In this Challenge Act, the player, who controls Classic Sonic, must run through a slightly-altered former half of Green Hill Act 1. The player must collect Power Sneakers to run faster through the Challenge Act, as they have a certain time to get an "S" Rank. Badniks, such as Moto Bug, Buzz Bomber, Buzzer, and Crabmeat, appear in the Challenge Act to make things difficult for the player. However, if the player can reach the Goal Plate within a minute and ten seconds, the player will receive an "S" rank.