Section 9.4 Of The Training Manual

So I'm studying using Trucking Truth's manual and I have an issue with a particular question. I'm in Virginia so I had originally downloaded the manual that the state DMV has on their site. I just prefer Trucking Truth's review on each page, so I've been using that. My issue is with "stopping distance' earlier we learned that total stopping distance is perception + reaction + breaking distance. At 55mph, good brakes, good driving conditions total stopping distance is over 300 feet.

However when we got to Air Brakes we are told that we need to add Brake lag. At 55 mph in the aforementioned conditions we need to add 32 feet.

In the Virginia manual the numbers are quite different. At 45 mph stopping distance is 346', at 55 mph it's listed as 451'.

Now in section 9.4 of trucking truth the following question is posed in the review. For an average driver traveling 55mph under good traction and brake conditions, total stopping distance *using air brakes* will have a stopping distance of:

The only 2 answers it could be is either 300' if you go by trucking truth or 400' if you go by the Virginia manual. Here's my gripe, if total stopping distance *without* air brakes is over 300' shouldn't we get an answer that allows us to show that we know there will be increased stopping distance if air brakes *are* in use? And I'm assuming that for the test in Virginia I should use the Virginia numbers, correct? All input would be appreciated. Thank you.