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How Truck Escape Ramps Stop Out-Of-Control Big Wheelers - YouTube
Channel: Business Insider
[3]
Oh! He took it!
[5]
He took it, dude!
[7]
Gravel is flying!
[9]
Dirt is flying!
[12]
Narrator: If you've driven any one
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of the many highways
crisscrossing the world,
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chances are you've seen one of these:
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a truck escape ramp.
[20]
Some escape ramps slope upwards.
[23]
Others are flat.
[25]
Some contain sand, others gravel.
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But regardless of design,
they all serve one purpose:
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to bring vehicles with
malfunctioning brakes to a safe stop.
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Just how do they work?
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When designing a new
ramp, state authorities
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consider factors specific to the road,
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like how steep the grade
is and what road conditions
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look like at the bottom of a hill.
[49]
Though they may look different
[51]
depending on where you see them,
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escape ramps around the world
do have some things in common.
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Most escape ramps make
use of arrester beds,
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pools of sand or gravel.
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The material in the bed is selected
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for their low coefficients
of interparticle friction,
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meaning when a wheel or
axle touches the bed,
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the material in it moves
away from each other,
[74]
allowing the truck to sink into the gaps.
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Like a swimming pool, escape
ramps are shallow at entry,
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anywhere from 3 inches
deep, and get deeper,
[86]
to around 48 inches at 100 to 200 feet in.
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When a truck enters the bed,
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it meets little resistance at first,
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then more as it travels.
[98]
This means the truck
decelerates gradually,
[100]
reducing the risk of injury to the driver,
[103]
and stands less risk of
flipping over, or capsizing.
[108]
When observing escape
ramps around the world,
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three designs stand out:
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the sandpile bed,
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the gravity escape ramp,
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and the mechanical arrester ramp.
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This is a sandpile bed.
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This type of escape ramp
contains loose rows of sand
[125]
perpendicular to the direction of traffic.
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As a truck collides with the pile,
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the energy of the truck is
transferred to the sand.
[133]
As the sand is sent flying
away at high speeds,
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an equal and opposite force
acts against the truck,
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reducing its velocity.
[142]
Impacting sandpiles, though, is...
[144]
jarring,
[145]
putting the driver at
higher risk of injury,
[148]
which brings us to the
gravity escape ramp,
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distinguishable by its
gradually ascending slope.
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In addition to the friction
of material in the bed,
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gravity works on the truck,
pushing it down and back.
[161]
The sloped gravity ramp is more effective
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than a flat arrester bed.
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A 10% grade could allow a truck
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to halt anywhere up to 85 feet sooner.
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Gravity ramps are the most cost-effective
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where natural rises occur
adjacent to the road.
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Some terrains, though, simply do not allow
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for a naturally occurring
gravity escape ramp.
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So, state agencies have turned
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to a more experimental
form of escape ramp.
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The mechanical arrester ramp
can be installed on flat ground
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or even downward slopes.
[194]
Unlike other designs,
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this ramp does not have an arrester bed.
[198]
Instead, it contains a series
of stainless-steel catch nets.
[202]
The nets absorb the energy
from a truck collision.
[206]
Like a rubber band being pulled taut,
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the force exerted on the
truck increases exponentially
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the further the truck travels.
[214]
The mechanical arrester
ramp then can stop a truck
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more quickly than gravel
or sand arrester beds.
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Entering a truck escape
ramp is a one-way trip.
[225]
If the ramp works properly,
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a truck will either end
up submerged or damaged,
[229]
needing a tow to recover.
[232]
Despite the expense,
agencies urge truck drivers
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and other motorists to
use the escape ramps.
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