How much time to stop a fully loaded semi

[dullard]

As an approximation, how much TIME does it take to stop a fully loaded semi? Assume normal conditions, assume highway/interstate speeds. I see lots of vague distance measurements which can roughly be used to calculate the time. However, the distance measurements are so vague, and I don't know if the braking acceleration is constant, so that the time I calculate could be quite off. Is 6-10 seconds a good estimate?

 

[acemcmac]

They had a 12+ fatality wreck on the Sure-kill Deathway (I-76) out here in Philly a few years back because of this...

 

[spidey07]

I'd guess more in the 6-7 second range. Notice the keyword "guess".

 

[Whoozyerdaddy]

Fuly loaded with what? Marshmellows don't weigh as much as lead.
Highway speeds? 55? 65? 75?
Single trailer or double?

Three seconds is way off regardless of your answers to the above questions.

 

[dullard]

Originally posted by: Whoozyerdaddy
Fuly loaded with what? Marshmellows don't weigh as much as lead.
Highway speeds? 55? 65? 75?
Single trailer or double?

Three seconds is way off regardless of your answers to the above questions.

Ok, lets go 65 mph, single trailer, loaded with a typical legal limit of weight, cold brakes.

 

[Rubycon]

All you need is a strong wall. :laugh:

Text

It's much harder to stop a ship displacing 93,000 tons from full speed of 25.6 knots (29.44 mph) - we can do it in approximately two and a half ship lengths which is about 2,412 feet.

 

[MedicBob]

FYI, 80,000 lbs is the usual legal limit without a permit. I would say with time included for reaction and recognition about 10 seconds.

 

[JulesMaximus]

Originally posted by: dullard
As an approximation, how much TIME does it take to stop a fully loaded semi? Assume normal conditions, assume highway/interstate speeds. I see lots of vague distance measurements which can roughly be used to calculate the time. However, the distance measurements are so vague, and I don't know if the breaking acceleration is constant, so that the time I calculate could be quite off. Is 3 seconds a good estimate?

Breaking? What is broken on it? If something is broken you can't really deduce fair stopping times until you fix whatever is broken and everything is functioning normally.

 

[JulesMaximus]

Originally posted by: dullard

Originally posted by: Whoozyerdaddy
Fuly loaded with what? Marshmellows don't weigh as much as lead.
Highway speeds? 55? 65? 75?
Single trailer or double?

Three seconds is way off regardless of your answers to the above questions.

Ok, lets go 65 mph, single trailer, loaded with a typical legal limit of weight, cold breaks.

There's that word break again...I don't understand. Cold breaks...so, did you freeze a part and break it?

 

[Rubycon]

Originally posted by: JulesMaximus

There's that word break again...I don't understand. Cold breaks...so, did you freeze a part and break it?

I can assure you that barrier breaks the truck.

 

[dullard]

 

[z0mb13]

less than 1 sec if the semi hits a concrete wall

 

[SampSon]

I saw this one discovery show a while back where they were developing this new system to help semis stop quicker. The system involved a few large rubber mats that would unroll and deploy under the semis wheels in order to increase braking surface area and counteract the rolling action of the wheels.

If I remember correctly it took from 10-20 seconds to fully stop a typical semi tractor-trailer.

 

[Rubycon]

Originally posted by: SampSon
I saw this one discovery show a while back where they were developing this new system to help semis stop quicker. The system involved a few large rubber mats that would unroll and deploy under the semis wheels in order to increase braking surface area and counteract the rolling action of the wheels.

If I remember correctly it took from 10-20 seconds to fully stop a typical semi tractor-trailer.

That seems like a lot of work.

 

[randay]

Is the treadmill rolling in the same direction as the semi? or the opposite direction? Also how fast is the treadmill rolling?

 

[mzkhadir]

http://www.ortrucking.org/stopping.htm

approximations Speed Reaction/Braking Distance Total Stopping Distance

30 mph 33' / 67 100'

40 mph 44' / 125 169'

55 mph 60' / 275' 335'

60 mph 66' / 360 426'

65 mph 71' / 454' 525'


* Above estimates are for 80,000 lb., loaded tractor-trailers traveling on a dry, level road. Source: National Safety Council's Defensive Driving Course for Professional Truck Drivers.

 

[bigfil]

Originally posted by: MS Dawn
All you need is a strong wall. :laugh:

Text

It's much harder to stop a ship displacing 93,000 tons from full speed of 25.6 knots (29.44 mph) - we can do it in approximately two and a half ship lengths which is about 2,412 feet.

holy crap id hate to be driving that truck when it hit that wall
hehe

 

[jagec]

Originally posted by: MS Dawn

Originally posted by: JulesMaximus

There's that word break again...I don't understand. Cold breaks...so, did you freeze a part and break it?

I can assure you that barrier breaks the truck.

especially one with bad brakes.

 

[dullard]

Originally posted by: mzkhadir
http://www.ortrucking.org/stopping.htm
approximations

At least that is a bit better than the vague "football field" distance that I've been seeing. And it separates out the reaction time (meaningless to this question) and the actual braking time.

So if we assume braking acceleration, a, is constant, then:

• v1 = v0 + a*t
  
  a = (v1-v0) / t

Now for the distance

• d1 = d0 + v0*t + 0.5*a*t^2
  
  v1 = 0 mph, v0 = 65 mph
  
  d1 = 454 ft (since I wanted just the braking time), d0 = 0 ft
  
  d1 = v0*t + 0.5* (-v0)*t = 0.5*v0*t
  
  t = 2*d1/v0 = 9.5 sec.

But, do semis have constant braking acceleration?

 

[mugs]

When I first read the title I thought this was going to be about guns