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# Speed Dependent Spike Strip

If the car's going under 25 MPH the spikes have time to retract.
 (+10, -2) [vote for, against]

If the car's going faster than 25 MPH, BLAMMO!

Real easy to make. The spikes have pnumatic cylinders under them that take a measure of time empty and allow the spikes to retract unless they're pushed too fast.

When idiots go blasting down my street where children ride their bikes and walk their dogs, I really wish we had this. Unfortunately, the world's probably not ready for martial law in the area of speed enforcement.

Damn shame.

 — doctorremulac3, May 12 2011

What? It could happen... No, really! [Grogster, May 17 2011]

[normzone, May 18 2011]

Or maybe deconstruct the road so offending vehicles shake themselves to pieces, when going too fast. [Vernon, May 22 2016]

How about a traffic light timing system that puts more red lights in your direction of travel when your speed is too high?
 — not_only_but_also, May 17 2011

 Hi [docremulac], I like this idea. + However, I shall attempt to find a flaw. Not to cultivate scorn, but to help flesh out this novel idea. The flaw is this:

 Depression rates will be dependent on wheel size as well as velocity.

 I could be wrong. I'm pilfering through a series of gedanken right now trying to figure this out.

There is a high probability that the differences in depression rates based on wheel size will be negligible. We need a mathematician, damnit!
 — daseva, May 17 2011

If the tyres burst then the car may crash. Not the desirable outcome.
 — xenzag, May 17 2011

 Depression rates will be highly dependent on wheel diameter.

Perhaps the residents of your street could invest in a small govt. surplus armoured vehicle.
 — Twizz, May 17 2011

The other way to do it would be to have the spikes normally retracted, but pop them out and then back in again in the fraction of a second after a tyre crosses the strip (see maths below). Thus, cars travelling faster than a certain speed will have their rear set of tyres punctured because they crossed the strip too soon after the front set of tyres. The disadvantage of this scheme is that longer cars will be able to travel faster than shorter cars. The advantages are that it's safer to have a punctured rear tyre than a punctured front tyre, tailgaters will get their tyres punctured, and that unicycles will be able to travel as fast as they like.

(If the speed limit is 100km/h, or about 28m/s and the distance between the front wheels and the rear wheels is 2m then the spikes should pop up for about 2/28 seconds, or, to be safe, about 5 hundredths of a second.)
 — hippo, May 17 2011

 If the intention is to reduce accidents, consider this:

A speeding driver collides with a pedestrian, sending them sliding along the road. The sensor detects that the car and/or pedestrian are exceeding the prescribed speed. The sliding pedestrian then encounters a row of spikes. Ouch.
 — Twizz, May 17 2011

 I'm very much in favour of anything stopping speeders speeding all the way up to, ..Ooohhh say, irreparably damaging their vehicles but not actually harming the inhabitants. I also live on a 50kmh limit road but, as this road is in Germany, everyone ignores that rule and bombs past at anything up to 100kmh (especially at night, waking us up - cheers).

 So +

 But - what about emergency vehicles? Even I will reluctantly allow that they should be able to drive a little over the speed limit.

What I'd really like is a little sign attached to my house that flashes up the word "Twat" at speeders. Wouldn't help at all but it would make me feel so much better.
 — squeak, May 18 2011

 How about plastic retractable road spikes and a professional-looking sign that says Warning - Spike Bump - Slow.

The people who live on your block will quickly know that it's a fake, but passers-through who speed by will be forced to slow down just in case.
 — phundug, May 20 2011

They will if they're prudent, cautious drivers, yes.
 — mouseposture, May 20 2011

 //Depression rates will be highly dependent on wheel diameter. //

Bollocks. I've got a jag with 19" alloys and guess what.
 — MaxwellBuchanan, May 21 2011

 //How about a traffic light timing system that puts more red lights in your direction of travel when your speed is too high?//

I'm told that they do this in Spain - apparently it works a treat because drivers in the queues at the lights start getting road-rage at the one who was speeding.
 — TomP, May 21 2011

Interesting. Actually, it's probably enough just to start the rumour that speeding cars result in more red lights.
 — MaxwellBuchanan, May 21 2011

You better just slow it down right there kind sir.
 — daseva, May 22 2011

you say "pnumatic", I say "custard".
 — methinksnot, May 23 2011

 Interesting approach. I see little plastic signs shaped like a kid and holding a little flag that some people put out that is sort of along those lines.

 I think I've mentioned before that I live in a town where you're not allowed to drive unless you're certifiably insane and people come blasting down my street in their hundred thousand dollar douchemobiles flooring it to show "they play by their own rules man!"

I've always told my kids don't assume cars don't see you, assume they're aiming for you and be prepared to get out of the way. Don't trust that stop signs, stoplights or crosswalks provide any magical barrier to a ton of steel coupled with a 200 horsepower engine and a psychopath.
 — doctorremulac3, May 22 2016

 // Interesting. Actually, it's probably enough just to start the rumour that speeding cars result in more red lights. //

 I tried to convince you on HB that "rhino horn harms your pecker" to which the responses were less than enthusiastic. I don't think that it is easy to start a rumour which is so easily to disprove.

 // Or maybe deconstruct the road so offending vehicles shake themselves to pieces, when going too fast. //

 We had this kind of road until a year ago. Now they are repairing it, and in a few month the motorcycles will start racing and crashing again, with way too high survival rates.

 //the world's probably not ready for martial law in the area of speed enforcement//

 // don't assume cars don't see you, assume they're aiming for you //

Welcome to the world of the avid cyclist. Every once in a while I dream of a cross-over between bicycle and a Kalashnikov. But since this would literally result in a pain in the ass (of someone, at least) I rather dream of softly whirring electric cars, motorcycles in sound-proof vacuum bubbles and motorized boom-boxes toppling over the pier like lemmings in search of the ever-alluring sirens.
 — Toto Anders, May 22 2016

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