Changing gears in a vehicle makes it go even faster.
During a car chase or race scene, if a driver already at top speed needs to go even faster, that's not a problem -- just shift gears, stomp on the gas, and the vehicle will suddenly surge forward with a new top speed that wasn't there a moment ago. It doesn't even matter what type of vehicle is involved; the mere act of changing gears is enough to make the car, motorboat, or hypergalactic spaceship suddenly hit Ludicrous Speeds. Of course, this doesn't work in Real Life; the transmission is not a magic lever that makes you drive faster. And a moment's thought will make it clear that a character who was already in a hurry should've been going as fast as they can before the gear change. In fiction, however, a Gear Shift Speed Surge is a convenient way to add drama to a race, or to Hand Wave the driver's sudden speed increase. Subtrope of Overdrive. Also see Traveling at the Speed of Plot.