From Sonic Retro
The Burst Dash is a move utilised by Sonic the Hedgehog and Blaze the Cat in Sonic Rush, Sonic Rush Adventure, and Sonic Colours (Nintendo DS). Closely related to the Sonic Boost from Sonic Unleashed the technique is activated by holding the or button while on the ground. Sonic and Blaze can rush forward and plow through enemies while depleting the Tension Gauge.
In both Sonic Rush and Sonic Rush Adventure, you can crouch and roll during the Burst Dash. This is useful when going downhill, as it allows for even greater speeds. Unlike the 3D Sonic Boost, the Burst Dash cannot be activated while in midair (the Air Boost Shoes enable this in Unleashed), but you can jump up once the Dash is already active.
The super-high-speeds of Burst Dashing are necessary to avoid death in several places during the Rush games, like when pursued by giant boulders as in the picture. In Sonic Colours, the dash is powered by White Wisps' "Hyper-Go-On energy", whereas in the Rush games Sonic and Blaze can charge it up simply by defeating enemies and performing tricks.