Cruise control & speed cameras

I can confirm I have all those features on my fatass-diesel-german-branded-notatallmustachian-SUV from 2016, so it’s nothing exceptional…

Fair enough, I’m no car expert and haven driven any latest ICE cars. Btw I hope these features trickle down to all cars soon, and that drivers use them. It’s annoying to put cruise control to 120 on Autobahn and then you catch up with a guy that does anything from 100 to 120. Then you overtake him and he suddenly does 130, so you have to really go over the limit to finish that overtaking. And if everyone put their tempomat to 120 it would be a much more pleasant drive…

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last year I rented a 2019 Tiguan (or Touran?) which have this feature on tempomat. When arriving faster than the car before it automatically decelerate, than come back to the previous speed when the car in front change lane (or go faster).

Everyone at 120 tempomat would be great, however :

  • Not all cars/tempomat systems have exactly the same calibration, it can vary
  • 120 km/h on your car doesn’t mean “real” 120km/h speed. You can see that with an additional GPS.
  • In Bern Canton it seems that every driver have his own speed limit he decide to go on any given day. It’s totally random but extremely constant at the same time. If it’s 80, then the BE will decide that for him, it’s 50 and that’s it. He’ll drive at 50.000km/h all day, without giving a damn about you become crazy behind him… :slight_smile: (sorry for the BE readers, but that’s so true… ^^)
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Yes that’s how it works in Tesla, too. But if a driver in front of you does 100, then 110, then 120, then again 100 for no apparent reason, and your car is glued to his back, it can be pretty annoying. After 10 minutes you know you’ve “lost” 1 minute already. I don’t mind if some other car is calibrated to do “120” at 117, if it’s constantly that speed. Doing “120” with 110 would be a fail, though. If the tyres have the right pressure, all cars should be pretty precise measuring the actual speed. What they show you should also centrally agreed upon (like, we will add 2% at all times). Why should every manufacturer do this differently?

First - it is not 100% up to manufacturers.
Different countries have different regulations on necessary speedo accuracy.
Most (clever ones) prescribe that it should never read below the actual speed. (US can/could read below, which is dumb).
And the upward tolerance is up to about 10% difference (EU, UK I believe).
Then the manufacturers need to comply, and they probably don’t all have the same technical setup (see below), so it’s hard to standardize so precisely.

Second - the moment you change your wheels/tires (e.g. 50% to 40% sidewall, as people like “low profile”), this should be recalibrated.
As the sensors are somewhere on the driveshaft/axle/wheel.
There is always going to be a margin of error involved.

I have my own different “margins” with summer and winter tires. :grin:
In winter (16" rims, bigger sidewalls) I can easily drive “128 km/h” according to my speedo, without passing actual 120 by the GPS speed.
In summer (18" rims, smaller sidewalls) it is closer to “124 km/h”.

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OK, I thought the wheels could make a difference. Thanks for the clarification. By the way, I see how GPS is not always reliable, in some valley or tunnel, so you can’t just equip all cars with it. But for example if you had some laser scanning the road under the car, similar to how a laser mouse works, would this not be precise enough regardless of the wheel setup?

Anyway, since speed is such a sensitive metric (you either get a speed ticket or not) and many drivers check their GPS to see how fast they can go, would it not be actually reasonable to precisely display the speed driven? Also, I hate how when a Blitzer in Zurich once measured 52 km/h and I got the fine. How is that protecting anyone? I think law enforcement should focus on racers, people who exceed speed limit by 20%+ and not by 1-2 km/h.

Other example: I was once on an Autobahn, doing 67 km/h in a Baustelle (like all other cars), the limit was 60. I got 100 CHF ticket for doing 67 km/h on Autobahn :smiley: . But I digress… sorry.

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Well this means you where more driving about 57 km/h, and in a city environment this makes a difference
Driving 10km/h less will save lives - YouTube

One thing about dutch cities being so nice to walk and cycle is that cars are slowed down by different means of road layout and infrascture. (as well as separating networks for cycles and cars)

Oh. and videa is quite harsh, probably not for everyone.

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I was overtaking a bus on Europabrücke, a dual-lane road, where I was on the left lane. Can’t see how I would be saving lives by going slower in that situation, but I get your point in general. I just find it a frustrating experience to always look at the speed, I’d rather focus on the road.

In my VW Golf from around 2015 (and I guess even earlier models), there was also a speed limiter. It was supposed to limit maximum speed up to defined value, with a security feature of being able to drive faster if you push harder. This is at least what I understood from the manual, because I never used it. However, someone may find it useful.

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Always using it, especially since I got a pretty silent automatic car, where it is pretty easy to drive too fast. So as soon as I get into town, I put it in. And actually also on overland streets when coming back from Germany. Way too easy to get used to the 100 km/h on overland.

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Yes, especially if the car is a nice performer ;). What helps in my current car is HUD display, where I see current speed kind of in front of the car.

Are you speaking of regular cruise control (i.e. Tempomat) or something else? Regular cruise control (like in Tesla) will accelerate the car to a desired speed, but as soon as you brake, cruise control is disabled. So it’s impractical to use it in the city, where speeds vary between 30/50/60, where you brake all the time, and where you might not want to always accelerate to the full limit. I use cruise control sparingly, when in the city.

Actually in a VW (or any other of that group) you can set a speed limiter, which is much more practical in a urban environment (and even overland street). The tempomat with distance holder is only practical on an Autobahn (or similar wide street with no bends needing you to reduce speed).

Basically you have control over the speed like normal, but the car stops accelerating at a set speed (limit speed). So you can easily set your limiter at 50, and the car won’t go faster than that. There is an override if you press the gas pedal hard enough though so you can react to situations appropriately.

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That’s a cool feature. I need to google if Tesla has it too. It already knows the speed limit on the road I’m driving (and it’s usually correct, not always). So it would be trivial to implement.

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I think this feature is named “speed limiter”, not cruise control. Apart from that, even in my car from 2011 I have an adaptive cruise control, which breaks and accelerates automatically, depending on the situation on the road. With automatic gearbox it can stop and start the car automatically (e.g. in case of traffic jam). With manual gearbox it works down to 30 km/h if I remember correctly and then switches off.

But even the adaptive one, I rather don’t use in the city.

Yes, I think with the cars able to recognise the signs (or just based on GPS location) it is possible to configure automatic speed limiting up to the current limit.

I’m pretty sure Teslas do take the speed from GPS data as my car has a ±1km/h deviation from GPS regardless of 21“ summer wheels or 19“ winter wheels. I put my speed offset to 5km/h over the limit and never get flashed.

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