# How do the vehicle acceleration rules in Ultimate Combat work?

I'm looking through the Vehicles section in Ultimate Combat and I'm rather confused about vehicle acceleration.

I thought I understood it but then I read this section on acceleration and it confused me;

Accelerate (standard action): With a successful driving check, the vehicle’s current speed increases up to its acceleration (in 5-foot increments; minimum 5 feet), but no higher than its maximum speed. The vehicle can move forward or forward diagonally. In other words, each time a vehicle enters a new 5-foot square, it can choose any of its forward-facing squares—the ones directly in front or either of the squares directly forward and diagonal. This allows the vehicle to swerve. A driver who fails her driving check can only move into squares directly in front of the vehicle’s forward facing.

Emphasis mine. That's the part that really throws me off. If someone could explain this to me, maybe using an example, that'd be really appreciated.

Here is an example of why I'm confused;

If the PCs are controlling say, a galley, using the air currents. The acceleration of the galley would be 30 ft. If at the beginning of the turn, the vehicle is still and has a current speed of 0 ft. does the driver's check to accelerate increase the galley's speed to 30ft (since that's its acceleration) or does it increase to 5ft. and eventually, after enough checks increase to 30 ft. acceleration?