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# Quantized Speed for Cars

Round to the nearest 5 X/ph
 (+15, -9) [vote for, against]

I'm thinking it would be useful for cars to be set up such that their speeds get rounded to the nearest 5 mph/kph. This would be useful at highway speeds, and would kick in at, say speeds at/above 40 mph / 70 kph.

In practice, as you are driving on a busy freeway, you accelerate to 50 mph, then right to 55, then 60, 65. You cannot drive 57 mph or 63 mph. A computer chip inline automatically adjusts on the fly to the nearest 5. Installed in every other car on the road, this happens for all cars on the highway.

The result being that people who appear to be driving about the same speed as you are in fact will be driving the same speed, exactly, maintaining position on the road. Other vehicles will be moving consistently faster or slower. This will prevent 'cruise creep', where one car is driving about 1 mph faster than another and takes 2 miles to pass.

I think I did a crap job of explaining this, so if it's not clear, please ask.

 — waugsqueke, Jun 17 2002

[calum, Jun 16 2005]

I'm interested in how you get from 55 to 60 without driving at the 'impossible' speed of 57... ;op
 — yamahito, Jun 17 2002

*snork*
 — waugsqueke, Jun 17 2002

 I love it, and I think it would prevent a lot more than cruise creep.

 My main concern is, when a driver hits 55, will s/he be able to manually lock that in? Let's say he absent-mindedly accelerates a little further to 56. Will the chip warp him to 60 right away, or does the drive have a chance to prevent that and continue to round *down* to 55? Similarly, can the driver prevent suddenly lurching down to 50?

 Also, I think the rate of accelaration is important. I can't imagine a Porsche and and old station wagon behaving the same way, even with the same chip. So, again, how much control does the driver have over this chip (and I'm not talking about complete freedom to override which would, of course, defeat the purpose).

Maybe all cars should just lock in at 68 once they've been on the highway for 2 minutes?
 — tharsaile, Jun 17 2002

Doesn't seem very practical, due to speedos not being that accurate, and changes in speed created by hills, etc. You might combine it with some kind of radar to keep a constant distance from nearby cars, but even that isn't foolproof. I'm not convinced this is necessary or useful.
 — pottedstu, Jun 17 2002

yes yes yes - a driver control like cruise control, for when you don't want to go above 55 or some other speed. Sometimes you want to conserve fuel, or not have to work your engine too hard. I don't claim to understand but I need justification for being the one in the slow lane going much slower than everyone else and forcing big lorries to overtake me which they don't like because they don't like dipping speed because it takes more effort to get them up to speed again.
 — sappho, Jun 17 2002

 Speed limiters are commonplace on large tractor-trailer rigs and can be installed on private vehicles (to make sure little Johnny doesn't dragrace). The downside is that you don't have any 'oomph' if you need to get out of the way quickly.

I've considered posting an idea for a pre-set cruise control which would have a similar effect as this idea. Instead of having to get up to 55 and then set the cruise control, a keypad would allow you to enter 55 and gracefully accelerate you to that speed. It would otherwise work exactly like a regular cruise control.
 — phoenix, Jun 17 2002

 Gee, there are so many problems with this.

 1) People won't stand for it.

 2) Until you've retrofitted EVERY other car on the highway, you have nothing.

 3) You can know how many RPMs your wheel is turning to a millionth of a percent, but you can't know how fast you are traveling because you can't know the circumference of your tire (under/over inflation, variance in manufacturing, non-stock tires...).

 Not to mention the aforementioned inability of the engine to maintain speed uphill.

So there will be creep anyway. And since there is creep, you will have to back off a MPH, but you can't. You can only back off 5 MPH, which means the guy behind you has to also, and so on. Now we're in a worse situation than we started with.
 — jtgd, Jun 18 2002

Does this mean that in France we will have increments of 8.5 km. Seems a bit mad to me.
 — English Pete, Jun 18 2002

Even if you know EXACTLY the circumference of your brand-new PZeros, they grow slowly smaller as you unwind them mile after mile: so much for knowing your revs per mile. A tightly-calibrated Doppler speed sensor under the car might be a better choice - though vertical car motions could cause some excitingly fluctuated readings there, too.
 — elhigh, Jun 13 2005

Giant stepper motors.
 — bristolz, Jun 13 2005

The speed of any one car *is* quantized. But the size of the quanta depend on the mass of the car.
So, just ensure that all cars have exactly the same mass. Then, if you're going 54.00000000000000000000 00000000 0000000121mph and the guy in front looks to be going the same speed, you'll be confident that he's not actually doing 54.000000000000000000 0000000000 0000000119mph
 — Basepair, Jun 13 2005

 Nice, [base].

I'd fear [jtgd]'s last point (um, 5 I guess). Instead of requiring this for all cars, just market a simple cruise controll that is only stable at 5 mph increments. You can still slow down a little if the car in front of you is slower on a hill, but it slowly moves back toward a round speed. As soon as a few people get this, others can assume the car ahead's going a round speed and set their (older-model) cruise control appropriately.
 — Worldgineer, Jun 13 2005

Practical or not, this is the kind of idea I come to this website for. Very clever.
 — doctorremulac3, Jun 15 2005

 One "bump" of the "accel / set" button (normally one button for this on most cruise controls) = 1 mph on almost every single car I have driven.

 So, how hard is it to see that you OD says "57" and you bump it three quick times to get to the speed you want.

 Conversely, a "bump" of the "coast" button (the "turn on") will slow it by 1mph. So you can set your speed to be what you want in 1mph increments (spell?) and make it as specific as you would like.

 If you do not like creeping up on people then slow down, I have ZERO problem creeping up on people by driving 5 mph over the speedlimit, NOT JOKING.

 If you don't like people creeping up on you, speed up, heh...don't blame tickets on me however, your decision.

 Idea/Invention Seems needless but I will not go so far as to give you a bone.

 There is (of course) the Audi answer to this problem: Radar Cruise Control.

 http://autoweb.drive.com.au (continued...)

 /cms/A_2212/article.html quoting... "Another impressive feature is the A8’s optional radar cruise control system. Once set, the radar cruise system watches for cars in front and automatically adjusts road speed to maintain a preset following distance. The system controls both the throttle and brake but driver interaction is required for heavy braking situations." ...end quoting.

(sorry, had to break link or it wouldn't post and I do not know how to create a "link" if someone would tell me I will learn ;0).
 — McGyver, Jun 16 2005

 — calum, Jun 16 2005

 // So, how hard is it to see that you OD says "57" and you bump it three quick times to get to the speed you want. //

That's not the point of the idea.
 — waugsqueke, Jun 16 2005

Nice. I was about to do an anti-cruise creep idea of my own but you beat me to it ...
 — britboy, Jun 15 2007

 I'm can't say whether this idea would be useful or not, but to make sure all conforming cars match speed shouldn't be too much of a problem. The speedometers could be regularly calibrated whie in use either by GPS or communication with road-side devices - either timing a known distance or accurately measuring and communicating speed. If we know distance travelled per revolution to anywhere near the 1/100,000,000 accuracy promised by jtgd, that should be sufficient for most purposes. (1mm creep per 100 km).

And it isn't essential for all cars to have the system for it to be useful. If, say, 50% of the cars are actively using it, the drivers of the other 50% would probably just match speeds automatically.
 — Loris, Mar 04 2011

impractical and dangerous (+)
 — Voice, Mar 05 2011

 [annotate]

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