Gate

You may be looking for Transformation Gate.

The Gate is an object that appears in the World Tour mode of Sonic & All-Stars Racing Transformed. Gates are only map objects that diversify and separate certain missions and unlockables from each other. Gates are often scattered in each chapter of the the World Tour and require a specific number of stars to open them up, which can be obtained through completing missions before them.

List of gates

Sunshine Coast

Location	Purpose
	To separate the first two Race events from the rest of the Tour for difficulty balance.
	To separate the chapter Sunshine Coast from Frozen Valley.

Frozen Valley

Location	Purpose
	To separate the first few events from special map objects like a slot machine and unlocking Shadow the Hedgehog.
	To separate the chapter Frozen Valley from Scorching Skies.

Scorching Skies

Location	Purpose
	To unlock Console Mods for various characters.
	To unlock NiGHTS.
	To separate the chapter Scorching Skies from Twilight Engine.

Twilight Engine

Location	Purpose
	This gate is used to unlocked the other half of the map, leading to events that unlock Joe Musashi.
	To separate the chapter Twilight Engine from Moonlight Park.

Moonlight Park

Location	Purpose
	Leads to a set of events to unlock Gum.
	To unlock Gilius Thunderhead.
	To separate the chapter Moonlight Park from Superstar Showdown.

Superstar Showdown

Location	Purpose
	Separates the first few missions from the rest for a difficulty effect and for Unlocking Reala and various console mods.
	To unlock AGES and end the World Tour.