Vehicle Speed Limiters

(stella wood) #1
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(Paul Flinders) #2

I was just about to post this.

Big brother/nanny state stuff, but with the advent of technology that allows surveillance at this granularity you didn’t expect free will to be allowed in the 21st century did you?

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(Mat Davies) #3

If it were to work 100% of the time - is it an issue?

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(John Scully) #4

“I was just about to post this.” You’re just too slow Paul :wink:

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(Paul Flinders) #5

Apologies, will try harder :slight_smile:

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(Mat Davies) #6

As far as I am aware it is possible to legally drive faster the published speed on the public highway in UK - - - - If directed by a Police Officer in uniform (as with most UK road laws)

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(John Scully) #7

It seems the new systems will still be based on GPS and Road sign recognition. My Tiguan has both and neither are as accurate as I’d like. Though it is clever enough to show a 110 limit in 130 zones in France when it’s raining. Luckily the new system can also be overridden with a heavy foot if you need a quck burst of speed to avoid some situation. All in all I find adaptive cruise control, lane assist and emergency braking, etc. are brilliant (though the Tiguan has had a few false panics and I’ve turned down the sensitivity to minimum) but, despite having tried it in a Tesla, I’m not fully there on autonomous cars yet.

There’s is also talk of journey tracking for accident investigation purposes and I find the “spy in the cab” aspect of that a bit worrying. Just as I dislike the idea of phones, tablets and Alexa and Google Home Eavesdropping on you all the time.

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(Simon Armstrong) #8

I know, and appreciate, that some people share your dislike John but…what is it that bothers you? Just to put my stake in the ground - I couldn’t give a stuff :crazy_face:

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(Robert Hodge) #9

I wonder whether an exception will be made for vehicles used by the emergency services. I mean seconds count for a stroke victim, and it will be very embarrassing for the new police car to be unable to keep up with the older getaway car.

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(Jane Williamson) #10

We have both cruise control and speed limiting in my old Mercedes.
We use both.
Like you I do not like the idea of being spied upon in yet another situation appealing.
The one thing that I find worrying about this idea is how do you really know what speed you are doing?
The speedo and the tom tom vary by at least three kph.
My other worry is what ideas the governments are going to come up with to replace speeding fines?

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(John Scully) #11

Well, to be honest I even dislike that despite having cookies as disabled as possible and private surfing on etc. when I search for, say a certain product, bloody ads for that type of product pop up randomly all over the place for ages. Though it does seem less prevelent since Apple tweaked Safari. So the idea that one evening at home, within earshot of Alexa, I could casually say “we must pop over to Italy and buy some wine” and then for the next month I get bombarded on all devices with Italian wine ads, Booking.com Italian hotel ads and Google asking me “are we there yet” :slight_smile:
I’m only slightly less worried about it reporting my support for beheading Rees-Mogg at Tyburn and impaling his head on a stake pour encourager les autres.

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(John Scully) #12

Car manufacturers overestimate on purpose by a small percent on speedos, the GPS is accurate. Old Mercedes are the best Mercedes IMO. I drove a E class company car all over Southern Africa in th mid nineties and it took everything we threw at it. We were bouncing along beside Landrovers at times. I then bought a new CLK n Paris in '98 but the quality was nothing like the E class. I dumped the CLK for an R129 SL in 2000.

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(Paul Flinders) #13

True but they don’t have much choice given the tolerances that the speedos must adhere to by law (typically they are not allowed to indicate a speed slower than the actual road speed).

Also tyre wear changes the rolling diameter by about 5% over the tyre lifetime which affects the speedo reading (making it show higher than the actual road speed).

GPS can underestimate speed because it assumes a totally straight line between way points.

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(Bob Sivell) #14
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(Paul Flinders) #15

Very funny although I thought Audi drivers had somewhat taken on the mantle of king tossers on the road.

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(Bob Sivell) #16

They couldn’t hold that title against such strong competition

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(Mark Rimmer) #17

Not so, Paul. Velocity is a rate of change in position. Speed is a magnitude of velocity. So if you know two sets of positions at different times, you can find the average speed during that time. For example, at t0 , you are at the position ( x0 , y0 ), and at t1 you are at the position ( x1 , y1 ), then your average speed during t1-t0 is square root of (x1-x0)^2+(y1-y0)^2 because that’s the rate of change in position at that duration.

Now, if the difference between t0 and t1 is small enough, that is, if the GPS measures our positions very very frequently, it will create an illusion that our speed is calculated in real time. In reality, it is surveying our positions frequently and calculating the average speed for each interval.

It must be true - I nicked this off the internet!

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(Robert Hodge) #18

So technically speaking then ---- the GPS is stating what the average speed was a few moments ago rather than what the speed actually is now.

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(Mark Rimmer) #19

Yes. Let Chad Courtney from Intel explain:-

“The speed doesn’t have any effect on the timing performance, the GPSr gets it’s time stamps from the Sats at however long it takes to get from the Sat to the GPSr (at the speed of light) this doesn’t change by how fast you’re moving. Now, since you’re are using data from multiple Sats, and some of it may be 1s old, some may be 0.5s old, some may be 0.1s old, some maybe 0.0000001s old (it all depends on when it came in, which is all timestamped relative to one another so when it’s calculating now, it’s knows adds to each of their timestamps how long ago it was received) that oldest one is the least accurate and can through things off. So a GPSr unit can calculate say on the most recent 4 received, and know about the previously calculated trajectory and speed, and with more Sats information it may be use to give a bit more likely current position. Otherwise you will have some amount of lag. Which can be anywhere from 10th’s of a second to second or possible more depending on of frequently your GPSr is set to recalculate its position and how many Sats it can see. Seeing on 4 Sats will have less accurate and slower to update, than say one with 20 Sats like where the most recent for captures is like less the 0.2s apart.”

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(Peter ) #20

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