Author Topic: Odd behaviour from speed limit recognition  (Read 826 times)

culzean

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Re: Odd behaviour from speed limit recognition
« Reply #15 on: June 27, 2017, 01:13:41 PM »
I agree that if you stick to speed limit there are quite a few drivers that try to 'push you' into going faster by sitting close to your rear bumper,  doesn't work with me.

 It is a bit of a worry that car with speed sign recognition can suddenly decide to slow down without at least putting brake lights on.

Here are a some sites with complaints about both Tesla autopilot bad behavior  and Audi speed limit recognition problems

https://www.youtube.com/watch?v=mqpsbMCXSyc
https://forums.tesla.com/forum/forums/anyone-else-having-too-many-autpilot-close-calls
https://www.audiworld.com/forums/a4-b9-platform-discussion-212/speed-limit-auto-drive-2918391/
« Last Edit: June 27, 2017, 02:11:39 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

ColinS

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Re: Odd behaviour from speed limit recognition
« Reply #16 on: June 27, 2017, 08:09:34 PM »
It is a bit of a worry that car with speed sign recognition can suddenly decide to slow down without at least putting brake lights on.

This is not a jab at you culzean, just a general comment.

It's not breaking, it's just slowing due to lack of accelerator use, just like my driving instructor told me to do as I was approaching a reduction in speed limit.  In that way you are naturally down to the speed limit as you pass the signs (which is what you are supposed to do by law).

It has been argued elsewhere on the forum that you should avoid using the brakes to save fuel and general wear and tear.

I personally don't see such a driving style as dangerous in any way.  The person behind should be two seconds distance, minimum and paying attention to what is going on around them.

ColinB

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Re: Odd behaviour from speed limit recognition
« Reply #17 on: June 27, 2017, 09:08:33 PM »
It is a bit of a worry that car with speed sign recognition can suddenly decide to slow down without at least putting brake lights on.
It's not breaking, it's just slowing due to lack of accelerator use, just like my driving instructor told me to do as I was approaching a reduction in speed limit.  In that way you are naturally down to the speed limit as you pass the signs (which is what you are supposed to do by law).
Some misunderstanding here. Culzean is correct, that is what happens, and that's why I don't now use the "intelligent" speed limiter.

You are also correct that with appropriate anticipation in normal driving you should be at the speed limit before you reach the sign. But that's not the scenario I described in my earlier post. If you're using the "intelligent" speed limiter in (say) a 40 limit and the computer misreads a 20 sign on an adjoining road, then it thinks you're 20 mph over the speed limit. It responds by sounding a loud alarm and cutting the gas so the car starts to decelerate (it will be slowing down despite the brakes not being used). The rate of deceleration depends on factors such as the road gradient. And yes, the driver behind should have a two second gap and hence have time to respond, although he won't have the benefit of your brake lights to cue him that you're slowing down.

culzean

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Re: Odd behaviour from speed limit recognition
« Reply #18 on: June 27, 2017, 09:28:10 PM »
It is a bit of a worry that car with speed sign recognition can suddenly decide to slow down without at least putting brake lights on.

This is not a jab at you culzean, just a general comment.

It's not breaking, it's just slowing due to lack of accelerator use, just like my driving instructor told me to do as I was approaching a reduction in speed limit.  In that way you are naturally down to the speed limit as you pass the signs (which is what you are supposed to do by law).

It has been argued elsewhere on the forum that you should avoid using the brakes to save fuel and general wear and tear.

I personally don't see such a driving style as dangerous in any way.  The person behind should be two seconds distance, minimum and paying attention to what is going on around them.

The reason I posted the Audi link is that it shows that the Audi (and probably all systems) suffers from reading ( more likely misreading) speed limit signs that get picked up, normally on adjacent roads,  these can be posting a considerably lower limit and cause vehicle to slow down without warning following traffic via brake lights.

Also on the Tesla forum,  if the auto drive system  loses some of its normal 'cues' e.g. lines on the road, or picks up things that are not normal road lines but it sees them as such the car can do stupid things like swapping lanes or even going to other side road.  There are also cases where Tesla system has not 'seen' things like vehicles have stopped ahead and would have ploughed into them at full speed had the driver not braked the car manually. These auto systems are far from sorted.

As for using engine braking to slow a vehicle rather than brakes  - this may be good for fuel consumption but I was always told that brake pads are much cheaper than gearboxes,  and the gears, bearings and CV joints wear as much from slowing the cars weight down as they do from accelerating it.

« Last Edit: June 27, 2017, 09:57:56 PM by culzean »
Some people will only consider you an expert if they agree with your point of view or advice,  when you give them advice they don't like they consider you an idiot

andruec

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Re: Odd behaviour from speed limit recognition
« Reply #19 on: June 27, 2017, 10:02:56 PM »
It is a bit of a worry that car with speed sign recognition can suddenly decide to slow down without at least putting brake lights on.

This is not a jab at you culzean, just a general comment.

It's not breaking, it's just slowing due to lack of accelerator use, just like my driving instructor told me to do as I was approaching a reduction in speed limit.  In that way you are naturally down to the speed limit as you pass the signs (which is what you are supposed to do by law).

It has been argued elsewhere on the forum that you should avoid using the brakes to save fuel and general wear and tear.

I personally don't see such a driving style as dangerous in any way.  The person behind should be two seconds distance, minimum and paying attention to what is going on around them.

The reason I posted the Audi link is that it shows that the Audi (and probably all systems) suffers from reading ( more likely misreading) speed limit signs that get picked up, normally on adjacent roads,  these can be posting a considerably lower limit and cause vehicle to slow down without warning following traffic via brake lights.

Also on the Tesla forum,  if the auto drive system  loses some of its normal 'cues' e.g. lines on the road, or picks up things that are not normal road lines but it sees them as such the car can do stupid things like swapping lanes or even going to other side road.  There are also cases where Tesla system has not 'seen' things like vehicles have stopped ahead and would have ploughed into them at full speed had the driver not braked the car manually. These auto systems are far from sorted.

As for using engine braking to slow a vehicle rather than brakes  - this may be good for fuel consumption but I was always told that brake pads are much cheaper than gearboxes,  and the gears and bearings wear as much from slowing the car as they do from accelerating it.
You were either misinformed or misunderstood. That comment only applies to people generating excessive braking force primarily those who deliberately change down to increase braking effect but possibly also lifting off rapidly at a relatively high rpm in a low gear (eg; 20mph in 2nd and suddenly releasing the accelerator).

Any car that can't handle having the accelerator released at cruising speed in the appropriate gear (eg; 5th at 50mph) is not safe to be driven in the first place. There is absolutely nothing wrong mechanically in using the accelerator to adjust your speed. Where it becomes potentially damaging (and even dangerous) is using the transmission to brake the car. From the sound of it what the Jazz does is not going to harm it in the slightest. It could however catch out a thoughtless tailgater and confuse the driver so has the potential to be dangerous.

More info.

What a lot of drivers don't understand is that those of us skilled at operating the accelerator pedal and anticipation rarely have to do what is commonly referred to as 'braking'. We just constantly adjust our speed in small increments and decrements. The accelerator pedal is all we need to do that ;)
« Last Edit: June 27, 2017, 10:08:56 PM by andruec »

John Ratsey

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Re: Odd behaviour from speed limit recognition
« Reply #20 on: June 28, 2017, 05:20:50 PM »
When intentionally decelerating I often use a very gentle touch of the brake pedal to signal to those behind that I am slowing down (this assumes that the gentle touch is sufficient to put the brake lights on but doesn't actually apply the brakes). I find it entertaining to be travelling in a traffic queue and trying to keep a decent gap between myself and the vehicle in front and just varying the accelerator to adjust the speed while the vehicle in front (usually tailgating) is having to use its brakes.

Getting back on topic, I only use the speed limit recognition as a source of information which is usually, but not always, correct (except when the signs are sparse and it changes to --). I wouldn't want to use it to control the speed.

ColinS

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Re: Odd behaviour from speed limit recognition
« Reply #21 on: June 28, 2017, 08:28:28 PM »
If you're using the "intelligent" speed limiter in (say) a 40 limit and the computer misreads a 20 sign on an adjoining road, then it thinks you're 20 mph over the speed limit. It responds by sounding a loud alarm and cutting the gas so the car starts to decelerate (it will be slowing down despite the brakes not being used). The rate of deceleration depends on factors such as the road gradient. And yes, the driver behind should have a two second gap and hence have time to respond, although he won't have the benefit of your brake lights to cue him that you're slowing down.
I absolutely see your point Colin.  This is, in my opinion, by far the most annoying aspect of it.  I have now learnt how to combat it though:  When the alarm sounds, dab the accelerator to the floor until you hear a prolonged beep (this will override the system), then manually control your speed at 40.  When you pass the next 40 marker it will kick in again.

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