I wanted to make sure I wasn't over-reading something.

Under acceleration, it gives a walking and running rate, which if I apply RAW would be movement in m/T. However, that just seems wonky, and I thnk RAI would have it as an acceleration rate. This came up at last weeks game.

So, if I had a vehicle with a 5/10/90 movement (assume running, no succ on drive & 1 IP). Is it:

Time............Turn 1.....Turn 2.......Turn 3......Turn 4
Move Ex 1....10 m.......10 m.........10 m.........10 m
Move Ex 2....10 m.......20 m.........30 m.........40 m

Which is it?

For reasons unknown to me the book calls the vehicle's walking and running rates acceleration (SR4A p. 167), when they actually are velocities. So the "running" vehicle remains at 10m/turn. Only with a test this speed can be increased.

I do not know if the vehicle remains at the increased speed if the driver does not roll equally well in the next turn or does not roll at all. However this would be the only way to ever reach the maximum speed.

I see no reason that the vehicle would slow down at the start of each Combat Turn. Otherwise, there is no way that anyone can get up to the 240 m/Combat Turn speed of the Eurocar Westwind 3K, or even worse, the 1000 speed of the GMC Banshee. It would require 36 hits per turn to keep up the max speed of a sports car (not likely to be very consistent), or even worse, 150 hits to even get to the max speed of a Banshee in the first place. Just because of the way the vehicle tables read, I would say that you stay at whatever velocity you were at already and then add the hits from the vehicle test, but it would be nice to get some confirmation.
EDIT: I just realized that the Vehicle Test adds 5 m to speed, not 10. Which, of course, makes the number of hits required to get up to maximum speed even more ridiculous.

The deceleration rate would also be interesting.

Yeah, I know the rules appear to read that the vehicle speed "resets" back to its walking or running rate, but that's just too crazy to comprehend that the rules would work that way.

To the OP, I run it as your example 2.