I'm a little confused about vehicle speeds. The BBB says that the acceleration number to the left of the slash is the vehicle's walking speed, and the number to the right is the running speed. But these values are a lot lower than the maximum speed for any vehicle, and a drive test to increase speed only adds 5 meters per turn per hit, so it's unlikely that a vehicle that you would think would be able to accelerate to its maximum speed rather quickly will even get there in any reasonable amount of time. Could someone please explain how speed and acceleration work with each other, and in general how fast vehicles move?

Vehicle has
Walking 5
Running 15,
Top Speed 3000

Turn One
Start at 0
0 + Walking = 5

Turn 2
Vehicle is already moving at 5
5 + Running 15 = 20

Turn 3
Vehicle is moving at 20
20 + 15 + (5 * 1 hit) = 40

Turn 4
Vehicle is starting at 40
etc ...

Walking and Running numbers are how much the current vehicle speed can change without requiring a vehicle test.

I was praying they'd fix this with the update to the rules, but they didn't. The Acceleration attribute has nothing to do with what we all know acceleration really means. Acceleration is your speed in tactical vehicle combat, which gets boosted by vehicle tests. Speed is your Chase speed. Other than your tactical movement rate being capped by your Speed, they have nothing to do with each other.

It's idiotic and I was praying that this would get changed in the next edition of the rules, but an average shmuck on the street (Reaction 3, skill 0, +3 handling, +1 for driving with AR assistance, -1 for defaulting) sitting in a brand new Westwind, will smash his foot on the gas and the game mechanics will never allow him to go faster than 108kph in tactical combat.

I still don't think that's even what they meant when the vehicle rules were written. I've always played Speed as Speed and Acceleration as the rate at which you can change your current Speed. You can change it by the Walking rate with no test and no action, you can change it by the Running rate with no test and a Free Action, and you can spend a Complex Action to accelerate by the Running Rate plus 5 x (hits on Acceleration Test).

If that's not what they meant, then why, after 6 printings, and the new 4.1 update of the rules, haven't they changed what the rule says to reflect it?

That is a working assumption, and methodically an absolutely valid interpretation: We all know what acceleration is, and if you use the acceleration values accordingly, the rules work. Replace troublesome definition with common understanding.

Listen, the rules work for what they were intended to do, which is keep track of a chase where both vehicles aren't performing to their maximum. They are both in traffic, or forced to go slower to avoid obstacles or whatever. Honestly, when in Shadowrun are two vechiles going to be chasing each other with absolutely no impeading factors?

If two drones are in the air and over the pacific, then keep track of their actual speed instead of making the pilot test at the start of every round, and their distance from each other. Maximum speed and acceleration will become VERY important then.