## What-if 0061: "Speed Bump"

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Eutychus
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### What-if 0061: "Speed Bump"

Speed Bump
How fast can you hit a speed bump while driving and live?

Myrlin Barber

Speed bumps vs chicane debate time?
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Icalasari
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### Re: What-if 0061: "Speed Bump"

This doesn't actually answer the question in my mind. I mean, he never answered what speed it would take

Assume an indestructible car, wheels, etc., and an indestructible speed bump. The car will not lift off, can ignore drag, etc. So then, at what speed, will the jolt be fatal?

Klear
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### Re: What-if 0061: "Speed Bump"

The 2nd American Conference on Human Vibration. What.

rhomboidal
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### Re: What-if 0061: "Speed Bump"

A road near my home has five speed bumps in a row. It's technically no longer a street, it's a steeplechase course.

Mikeski
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### Re: What-if 0061: "Speed Bump"

Icalasari wrote:This doesn't actually answer the question in my mind. I mean, he never answered what speed it would take

Assume an indestructible car, wheels, etc., and an indestructible speed bump. The car will not lift off, can ignore drag, etc. So then, at what speed, will the jolt be fatal?

The answer is "there is no answer". Sitting in a car with tires, suspension, and a cushy seat (and your own "cushy seat"), you can't hit one fast enough to kill you by blunt-force trauma applied through the tuchis. (And you have to figure out how much of the force is delivered there, as opposed to through the legs and arms which are probably on the floorboards and armrests/steering wheel.)

As soon as you start specifying "enough wings to hold it down", "operating in a vacuum so there's no air resistance", "enough thrust to hit the required ludicrous speed", etc., you're not really talking about speed bumps and cars anymore. You're talking about how to land a rocket on the moon without decelerating before touchdown.

The what-if question about killing (or not) a human this way is probably better phrased as "what are the practical limits of an #\$%-kicking contest?" or "how far can a human fall and land on his bum and survive?".

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### Re: What-if 0061: "Speed Bump"

The average modern car is limited to a top speed of around 120 mph, and the fastest can go about 200.

There is a not insignificant list of cars that can significantly break the 200mph barrier.

Bugatti Veyron will go 250-265 mph depending on the edition

Rombobjörn
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### Re: What-if 0061: "Speed Bump"

The ET reference made me giggle – once I figured it out, which took a while.

kasmeneo
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### Re: What-if 0061: "Speed Bump"

In Kenya, there actually are speed bumps on highways. And it's good they're there, because they make people slow down before the zebra crossings across those highways. ("Zebra crossing" as in "pedestrian crossing", not as a reference to african wildlife.)
It's cooler up here.

dalcde
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### Re: What-if 0061: "Speed Bump"

In the state of Pennsylvania, drivers may have \$2 added to their speeding ticket for every mile per hour by which they break the speed limit.[14]

Just in case someone is looking through the document, the regulation is found on page 219 of the document (225 of the pdf), in footnote 412.
[\$42.50] Plus an additional \$2 for every mph in excess of 5 mph over the speed limit [65 mph].

Good news is that your driver's license will not be suspended for more than a year.

dalcde
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### Re: What-if 0061: "Speed Bump"

kasmeneo wrote:In Kenya, there actually are speed bumps on highways. And it's good they're there, because they make people slow down before the zebra crossings across those highways. ("Zebra crossing" as in "pedestrian crossing", not as a reference to african wildlife.)

Zebra crossings in highways? Never heard of it.

TimmyTurner
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### Re: What-if 0061: "Speed Bump"

Like anyone with a physics background, I do all my calculations in SI units, but I've gotten too many US speeding tickets to write this article in anything but miles per hour; it's just been burned into my brain. Sorry!

If the numbers are available, why not give them in the article (additionally)? I (and probably most readers except UK and USA) could not make sense of the article before reconverting the units.

Klear
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### Re: What-if 0061: "Speed Bump"

kasmeneo wrote:In Kenya, there actually are speed bumps on highways. And it's good they're there, because they make people slow down before the zebra crossings across those highways. ("Zebra crossing" as in "pedestrian crossing", not as a reference to african wildlife.)

They have pedestrian crossings on highways? o.O

eran_rathan
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### Re: What-if 0061: "Speed Bump"

\$1.14 billion [≈ box office sales of The Exorcist, 1973]

Which is pretty awesome.

ETA: And even MORE awesome, one of the options it gives is [≈ the box office sales of ET, 1982].
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cellocgw
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### Re: What-if 0061: "Speed Bump"

On the boring side of the analysis, I seem to recall a few years back someone was developing an active suspension system which measured the angle of the bump (and thus the rate of rise of the tire/wheel) and adjusted the shock absorber's damping coefficient. The idea was to ensure that none of the impulse force passed thru to the body of the car. An idealized version of such a system, along with indestructible tires, would allow you to go at arbitrary speeds and never even feel the bump.

Obligatory:
Spoiler:
Just don't try driving through grapevines with molpies in the car.

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Klear
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### Re: What-if 0061: "Speed Bump"

\$1.14 billion [≈ box office sales of The Exorcist, 1973]

Which is pretty awesome.

ETA: And even MORE awesome, one of the options it gives is [≈ the box office sales of ET, 1982].

...and since I'm using the Dictionary as well, the quote in your posts says this:

\$1.14 billion [≈ box office sales of 101 Dalmatians, 1961] [≈ box office sales of The Exorcist, 1973]

...of course, I have just made it worse, with an additional box office stat.

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### Re: What-if 0061: "Speed Bump"

Klear wrote:
kasmeneo wrote:In Kenya, there actually are speed bumps on highways. And it's good they're there, because they make people slow down before the zebra crossings across those highways. ("Zebra crossing" as in "pedestrian crossing", not as a reference to african wildlife.)

They have pedestrian crossings on highways? o.O

Isn't something, by definition, not a highway if it has pedestrian crossings, or any other kind of crossings for that matter? I'm not exactly sure how most people define a highway, but my definition would be "A road with no at-grade intersections or traffic lights".
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eran_rathan
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### Re: What-if 0061: "Speed Bump"

Klear wrote:
kasmeneo wrote:In Kenya, there actually are speed bumps on highways. And it's good they're there, because they make people slow down before the zebra crossings across those highways. ("Zebra crossing" as in "pedestrian crossing", not as a reference to african wildlife.)

They have pedestrian crossings on highways? o.O

Isn't something, by definition, not a highway if it has pedestrian crossings, or any other kind of crossings for that matter? I'm not exactly sure how most people define a highway, but my definition would be "A road with no at-grade intersections or traffic lights".

It depends a large part on where you are, but highways are defined (in the US) as fee-simple rights-of-way for travel, access, and utilities that are owned by the state or federal government. They can be any sort of road (or certain navigable streams, in New England), with or without any control of access (CoA). Interstates are CoA highways that are owned by the federal government.

here we go:
http://en.wikipedia.org/wiki/Highway
http://en.wikipedia.org/wiki/Controlled-access_highway
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DavidGee
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### Re: What-if 0061: "Speed Bump"

In Kuwait, Expats in huge four by fours have it well circulated that the faster you go over a speed bump, the less you feel it.
Everyone has company cars, if not drivers, and 70-90 Km/h makes them entirely unnoticeable. Obviously the bumps are only really on residential roads so I've not tried beyond 110...

azule
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### Re: What-if 0061: "Speed Bump"

cellocgw wrote:ETA: WooHoo! The Post Number of The Beast!
Congrats on one Hell of an achievement. (*giggle* BlitzGirl has no dominion here!)

I mean: Speed bumps, when have they ever really helped? *pshaw*

Diadem wrote:Isn't something, by definition, not a highway if it has pedestrian crossings, or any other kind of crossings for that matter? I'm not exactly sure how most people define a highway, but my definition would be "A road with no at-grade intersections or traffic lights".
That's a freeway, buddy. Highways are simply roads that have a default speed limit of 55 (often unmarked with such speed limit). Freeways do have those requirements, though.

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teelo
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### Re: What-if 0061: "Speed Bump"

How many speed bumps can you build before you die of starvation or thirst?

mathmannix
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### Re: What-if 0061: "Speed Bump"

eran_rathan wrote:It depends a large part on where you are, but highways are defined (in the US) as fee-simple rights-of-way for travel, access, and utilities that are owned by the state or federal government. They can be any sort of road (or certain navigable streams, in New England), with or without any control of access (CoA). Interstates are CoA highways that are owned by the federal government.

There are also county highways in the U.S. and Canada - I know of some in Illinois.
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Klear
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### Re: What-if 0061: "Speed Bump"

eran_rathan wrote:
Klear wrote:
kasmeneo wrote:In Kenya, there actually are speed bumps on highways. And it's good they're there, because they make people slow down before the zebra crossings across those highways. ("Zebra crossing" as in "pedestrian crossing", not as a reference to african wildlife.)

They have pedestrian crossings on highways? o.O

Isn't something, by definition, not a highway if it has pedestrian crossings, or any other kind of crossings for that matter? I'm not exactly sure how most people define a highway, but my definition would be "A road with no at-grade intersections or traffic lights".

It depends a large part on where you are, but highways are defined (in the US) as fee-simple rights-of-way for travel, access, and utilities that are owned by the state or federal government. They can be any sort of road (or certain navigable streams, in New England), with or without any control of access (CoA). Interstates are CoA highways that are owned by the federal government.

Interesting. In that case, however, I don't see what's so surprising about there being speed bumps...

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### Re: What-if 0061: "Speed Bump"

eran_rathan wrote:It depends a large part on where you are, but highways are defined (in the US) as fee-simple rights-of-way for travel, access, and utilities that are owned by the state or federal government. They can be any sort of road (or certain navigable streams, in New England), with or without any control of access (CoA). Interstates are CoA highways that are owned by the federal government.

Legally true, I guess. But surely that's not the colloquial use? Nobody calls a dirt track or a inner city road a highway.

Perhaps it's a US thing. You guys are rather weird when it comes to naming roads.
You park on a driveway.
You drive on a parkway.
You do your high-speed driving on a freeway, which may or may not be free-access
You do your free-access driving on a highway, which may or may not be high-speed.
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Plasma Man
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### Re: What-if 0061: "Speed Bump"

But when it comes to driving while high, say "no way".
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Red Hal
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### Re: What-if 0061: "Speed Bump"

Actually, in most of the U.K. a highway is any way open to the public with a right of way. A motorway is a highway, and so is a single-track muddy path. In Scotland it is somewhat less relevant as we have the right to roam, so the concept of a highway really only applies to motorised vehicles.
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eran_rathan
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### Re: What-if 0061: "Speed Bump"

eran_rathan wrote:It depends a large part on where you are, but highways are defined (in the US) as fee-simple rights-of-way for travel, access, and utilities that are owned by the state or federal government. They can be any sort of road (or certain navigable streams, in New England), with or without any control of access (CoA). Interstates are CoA highways that are owned by the federal government.

Legally true, I guess. But surely that's not the colloquial use? Nobody calls a dirt track or a inner city road a highway.

Perhaps it's a US thing. You guys are rather weird when it comes to naming roads.
You park on a driveway.
You drive on a parkway.
You do your high-speed driving on a freeway, which may or may not be free-access
You do your free-access driving on a highway, which may or may not be high-speed.

Yeah, I was talking legally (hey, its my thing - roads and easements are a specialty of mine).

I blame the naming thing on the English, though
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### Re: What-if 0061: "Speed Bump"

The average modern car is limited to a top speed of around 120 mph, and the fastest can go about 200.

The Veyron does 267.

Therefore, if you drove a car over a Philadelphia speed bump at 90% of the speed of light, in addition to destroying the city ...

... you could expect a speeding ticket of \$1.14 billion.

Amusingly, someone I know was using this as the punchline to the "But officer, the stoplight looked green to me!" blue-shift joke just this past weekend.

5th Earth
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### Re: What-if 0061: "Speed Bump"

I would like to add, in the interest of pedantry, that not all cars are drag-limited. Some are limited by their gearing--they hit the redline in their top gear before atmospheric drag prevents further acceleration. It's uncommon, since these days most cars have tall gearing for fuel efficiency reasons, but for some race cars it's an issue.
It seemed like a good idea at the time.

keithl
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### Re: What-if 0061: "Speed Bump"

We may presume this is no ordinary car.

If the car stays on the ground, there is presumably some means to deflect all the air above the vehicle. Somehow, a vacuum is created underneath. Which also keeps the carbon-nanotube-belted radial tires from shredding in the supersonic slipstream.

So, imagine the wheels hit the speed bump very fast, perhaps 10,000 meters per second, the mass of rubber and metal compressing into the speed bump faster than the speed of sound in the materials (but not fast enough to initiate nuclear processes). The result will probably be a flash of X rays, and incandescent plasma blowing in all directions, some of which vectors into the passenger compartment. I'd guess the immediate ( 100 microsecond scale ) effect would be shearing off the driver's legs, followed by immolation in incandescent gasses.

As a rule of thumb, it is imprudent to pass over speed bumps faster than orbital velocity.

jpvlsmv
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### Re: What-if 0061: "Speed Bump"

Diadem wrote:Perhaps it's a US thing. You guys are rather weird when it comes to naming roads.
You park on a driveway.
You drive on a parkway.
You do your high-speed driving on a freeway, which may or may not be free-access
You do your free-access driving on a highway, which may or may not be high-speed.

There are Interstate Highways in Hawaii, Puerto Rico (neither of which are accessible by car from any other state) and Alaska.
Turnpikes are no longer access-limited by actual pikes needing to be turned.
People drive right by the "NO PASSING" sign. And they don't wait for the one that says "STOP" to change.
And of course, there's the rediculous sign "END CONSTRUCTION"... I never know if it's put there as a protest, or if the guys running the machinery would keep fixing the road past that point. (Hey Bob, we passed the sign. Oh s***, back up the steamroller)

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keithl
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### Re: What-if 0061: "Speed Bump"

Accelerating 1500 kg of car plus passengers to 90% of the speed of light requires 3e20 joules. Purchased as electricity from PECO, the Philadelphia power company, at 8.64 cents per kilowatt hour, that is a power bill of 7 trillion dollars.

eran_rathan
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### Re: What-if 0061: "Speed Bump"

keithl wrote:Accelerating 1500 kg of car plus passengers to 90% of the speed of light requires 3e20 joules. Purchased as electricity from PECO, the Philadelphia power company, at 8.64 cents per kilowatt hour, that is a power bill of 7 trillion dollars.

Dictionary of Numbers lists that as the direct cost of all US wars, ever (not including veteran's benefits or interest).
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kasmeneo
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### Re: What-if 0061: "Speed Bump"

Klear wrote:
kasmeneo wrote:In Kenya, there actually are speed bumps on highways. And it's good they're there, because they make people slow down before the zebra crossings across those highways. ("Zebra crossing" as in "pedestrian crossing", not as a reference to african wildlife.)

They have pedestrian crossings on highways? o.O

Yes, I found that quite hilarious too. They don't bother building any footbridges or tunnels for pedestrians to cross.

Diadem wrote:Isn't something, by definition, not a highway if it has pedestrian crossings, or any other kind of crossings for that matter? I'm not exactly sure how most people define a highway, but my definition would be "A road with no at-grade intersections or traffic lights".

Highway as in "major connecting road between large cities, with 4 or more lanes". In that case, the A2 from Nairobi northwards. Unfortuately I didn't snap a photo...

...edit: but I found a video (not mine): http://www.youtube.com/watch?v=rtxgbGwZ5rc
Scroll to 2:55 and you'll see the speed bump and the zebra crossing with pedestrians waiting.
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thenameipicked
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### Re: What-if 0061: "Speed Bump"

Anybody else notice that his math was wrong?
670,000,000 * \$2 != 1.14 Billion, but rather 1.34 Billion.

eran_rathan wrote:
ETA: And even MORE awesome, one of the options it gives is [≈ the box office sales of ET, 1982].

...so maybe it was an additional reference to ET?

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### Re: What-if 0061: "Speed Bump"

keithl wrote:As a rule of thumb, it is imprudent to pass over speed bumps faster than orbital velocity.

I'll totally sig this

davidstarlingm
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### Re: What-if 0061: "Speed Bump"

The official nomenclature I've always seen is:

• Highway: any road that the state is responsible for maintaining
• Limited-access highway: Highways with on-ramps and off-ramps
• Driveway: any road on private property

dalcde
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### Re: What-if 0061: "Speed Bump"

Terminology I use:
Highway: Road where you can drive very fast (no traffic lights/pedestrian crossings etc.)

But apparently WIkipedia says that
Traditionally highways were used by people on foot

lgw
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### Re: What-if 0061: "Speed Bump"

eran_rathan wrote:It depends a large part on where you are, but highways are defined (in the US) as fee-simple rights-of-way for travel, access, and utilities that are owned by the state or federal government. They can be any sort of road (or certain navigable streams, in New England), with or without any control of access (CoA). Interstates are CoA highways that are owned by the federal government.

Legally true, I guess. But surely that's not the colloquial use? Nobody calls a dirt track or a inner city road a highway.

Perhaps it's a US thing. You guys are rather weird when it comes to naming roads.
You park on a driveway.
You drive on a parkway.
You do your high-speed driving on a freeway, which may or may not be free-access
You do your free-access driving on a highway, which may or may not be high-speed.

In a lot of US neighborhoods these days, the association will give you a ticket if you park in your driveway, but it is an odd term - presumably it's the non-road place you drive on to get to the garage.

Parkways are ways through parks, or park-like greenery.

Highways are "high" in the sense of "prominent or important", not in the sense of speed or elevation. A highway is a main road. "High street" was the common term before highway, and remains the most common street name in America.

Freeways are "free-as-in-beer", a freeway is not a toll road.
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pitareio
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### Re: What-if 0061: "Speed Bump"

Just to play the nitpicking maths nazi :

- 670,000,000 mph is 99,9% the speed of light, not 90% (but well, as long as it's under 100%...)
- \$2 per extra mph at this speed would be \$1.34 billion, not 1.14 (about \$1.2 billion if you do 90% the speed of light)

rmsgrey
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### Re: What-if 0061: "Speed Bump"

Either no-one hits a speed bump and lives, or everyone does, no matter how fast (just not for very long)