Speed Highway

Speed Highway (スピードハイウェイ) is one of the action stages playable in the game Sonic Adventure and Sonic Adventure DX: Director's Cut.

Overview
Speed Highway is accessible after completing the stage Twinkle Park, you can only enter this stage via an ID card found in front of the hotel. This stage is composed of three sections: The first section takes place far above Station Square in the dead of night, among skyscrapers and highways, the mid-section, which has Sonic running down a skyscraper and dodging helicopters also takes place at night, and the ending section, which seems to take place in another area of Station Square (with quite a bit of traffic), that takes place just after a sunrise (hinted at in the name of this area's music track, "At Dawn").

Sonic
When playing as Sonic the Hedgehog, your goal is to blast through this stage an release the animals in the capsule. Most of the stage is held at night. In contrast to this being Tails' final stage and Knuckles' first, this is halfway through Sonic's story.

Tails
When playing as Miles "Tails" Prower, you must race Doctor Eggman to the end of the stage to prevent him from detonating the missile. His stage only contains the first section of Sonic's stage, but a glitch allowed Tails to play the latter two sections of Sonic's stage. This is Tails's last stage, and the difficulty on beating Eggman to the missile is hard, so it is recommended to take numerous shortcuts for an easy win.

Knuckles
Knuckles the Echidna begins the level searching for the 3 pieces of the Master Emerald in the lower area of the city, which is the daytime area of Sonic's version of the stage, also with the same music from the end of the stage. There are many hazards in this level, such as futuristic-looking, hovering police cars that will come and try to attack you (unlike the other flying robots which just stay in their place), making it difficult to achieve one of Knuckles to complete one of his other missions: to get the 3 emerald shards without being hit or losing rings. The difficulty on this is easy, but with many hazards.

Trivia

 * This stage will reappear in the game Sonic Generations.