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Comment by briffle | Hacker News Reader

Family Member is head of training for very large fire department. For testing their truck drivers, if they ABS kicks in at all, you fail the test. They want you to go all the way up to the limit, and ease off the breaks slightly as the 60,000lb truck gets close to kicking in its ABS.

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Is ABS a feature on their training truck that doesn't exist on the real rigs, or something?

I've read about police receiving the opposite instruction: a reminder during training that they should keep their foot on the brake when they feel the ABS coming on. Apparently too many police were crashing because they'd lift, and attempt threshold braking as they'd been trained back in the day, when they felt the ABS coming on. They were interpreting the feel of ABS as a loss in traction.

All modern fire trucks have ABS.

The ABS does allow better control if you break traction, but lenthens your stopping distance. They want their drivers to not break traction, and keep the stopping distance short. Big difference between a Subaru slamming into you because it couldn't stop fast enough, and a firetruck loaded with 1500 gallons of water, etc, slamming into you.

Have they done a side-by-side test? Or was that based on some information from years ago? If they don't break traction, how do they know they're braking enough?

If this is a modern ABS system I'd be shocked if they could beat it. See this short video comparing a 20 year old (at the time) vs modern semi-trailer weighing 38.5 metric tons (84,000 lbs). https://www.youtube.com/watch?v=Vo6C3HEpfsQ

I suppose my initial feeling towards the idea that a driver can consistently better the performance of their vehicle's ABS is strong skepticism, but, I wonder if it's less difficult on a really massive vehicle. Or if the ABS on one of those more massive vehicles (reliant on drum brakes) is simply not as effective as one would like.

Interesting stuff.

Well an average driver probably not, but i might trust a professionally trained driver who drives everyday in high stress situations accelerating and breaking with maximum efficiency at all times.

This is called "threshold braking" (though it's often incorrectly called "pumping the brakes") and was/is standard practice for vehicles without ABS.

I learned that 'pumping' is what you do to counteract the brakes overheating when going down a mountain and engine braking isn't sufficient.

Pumping the brakes is what you do if you cannot threshold brake. You lose traction, so let off the brakes to regain grip, then apply again and repeat, hence pumping.

Well that makes some sense for training professional drivers, which most people are not.

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