Auto Running

Auto Running is a recurring game mechanic in the Sonic the Hedgehog series.

Description
Auto Running involves the character moving forward automatically using a "on the rails" style movement, across an open path while the player controls the character's left-to-right movement and attacks. This mechanic has been used to help create a feel of speed for the player as Sonic runs.

Sonic the Hedgehog 3
In the first zone, Angel Island Zone, one auto running section occurs when you're being chased by the Flying Battery which lasts until the battleship's ammo is lowered. It flies away before the boss battle with Flame Mobile.

Sonic & Knuckles
There's only one auto running section in the whole game and it occurs in Mushroom Hill Zone during the second act's boss fight.

Sonic Adventure
Auto running occurs in the Sega Dreamcast game Sonic Adventure. It is used during the second phase of Speed Highway where Sonic runs down a tall skyscraper and the player must control him by maneuvering him to the left and right to avoid obstacles.

Since Speed Highway appears in Sonic Generations, the auto running phase is present.

Sonic Advance 2
Auto Running was used in all the bosses of the game (the sole exception being the final boss) and received much criticism because of the lack of control.

Sonic the Hedgehog (2006)
Auto Running was used in the "Mach Speed Levels" in Sonic's story. This was done to create a feel of excitement and sense of Sonic's maximum speed for the player which it does for some.

Sonic and the Secret Rings
Auto Running was used in all the Adventure levels in the game. In this game you can customize the speed of Sonic to fit the level, making this variation more enjoyable to some, while for others it was an annoyance since you can never freely control Sonic in the game.

Sonic Unleashed
Auto Running didn't play as huge of a role in Unleashed, but it was used throughout all the daytime sub-bosses and bosses of the game. Since it was only used during boss levels, it didn't receive any criticism.

Sonic the Hedgehog 4: Episode 1
Just like in Sonic & Knuckles, it occurs during a boss fight in Mad Gear Zone. Since the E.G.G. Station Zone has a boss rush event before the final boss, the same auto running section returns here.

Sonic Colors
Auto Running is used along with Quick-Step Mode in Sonic Colors. It is used during the Orcan/Skullian bosses as well as the final boss.

Sonic Generations
Auto Running in Sonic Generations takes place in the start of six Modern Sonic stages, during Speed Highway while running down the building, while being chased by the GUN Truck in City Escape, During the Egg Chaser sections in Rooftop Run, on the Silver Rival battles, and during the Egg Dragoon Boss battle.