I agree generally. The placement of the car would have to be precise to be effective unless the point was to squish the car :-) Very difficult at high speeds.
Brakes are designed only for the max GVW of the vehicle plus a fixed percentage (to brag about added safety). You won't find more than what the builder budgeted and they keep them costs down. Normally that's fine.
A semi could have twenty times more mass than a car (2 tons vs 40 tons) so the car brakes probably wouldn't have any significant ability to slow a semi. It would make the semi more unstable, a huge risk (not evenly braking could force a jackknife and car impact would be worse).
But note that all the truck axles have brakes so something went radically wrong with the entire system to allow this to happen. Or ALL the brakes were maladjusted. (Not likely, but with NAFTA who knows.) It will still fall on the driver and trucking company (operator error and/or maintenance). My guess is bad shoes or failure within the valve controls.
NAFTA is a mistake. You never know what the real condition of the truck is and you only hope the manifest is reasonably accurate (for foreign rigs primarily).
A siren on a freeway is useless but still required. What with cell phones (mostly still used without headsets and/or texting), A/C, tunes, road and wind noise, kids and/or their DVD players, better sound deadening (quiet ride), a 110db siren doesn't stand a chance until right off the rear bumper (I've been SO tempted at times). Add fatigue, impatience (speeding), zoning out and you'll get the reasons emergency vehicles have a hard time getting through traffic sometimes. Folks don't look around much either (my truck and fifth wheel are apparently cloaked and invisible, I'm adding air horns).
One of the best siren systems I ever used was roof mounted on an ambulance (rookies have to do time in the box) and the box wall behind the siren speakers reflected well to make more forward noise (hard on the occupants tho). I had cars pulling over two blocks ahead (huh? Wazzat you said?) I miss the old 'grinder' sirens too for tradition sake.
I often told myself that it oughta be that doofus' gramma/wife/kid we were responding to when he blocked us, but that isn't nice (I would discuss their parentage or lack thereof though in 'colorful' terms).
A siren isn't a toy (except at parades) it means someone is in trouble. Pretty basic stuff. My suspicion is that folks stopped caring (treat it as background noise and tune it out), until you're responding to THEIR call for help. We don't have to go THERE, it's too far off topic. ;-)
If more, please move it to the discussion group. Thanks!
Scenic and wildlife images
Blame the typos on the iPhone. It's awkward to type on one.
It's not a matter of the mass of the car vs. the mass of the truck, but of
the breaking force available in the car. I doubt a car could stop a big-rig,
but under the right circumstances the added braking might be just enough to
make the difference.
He'd be more successful siren-ing cars out of the way.
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