Intelligent Speed Assistance - speed warnings

[AndrueC]

On 5/5/2024 at 5:49 PM, Cyker said:

My most hilarious one so far has been when it thinks the speed limit is 20kph on a 40mph road  

If it beeps all the time then driving along the A75 in Dumfries & Galloway will be appalling. It's frequently signed as 40mph for HGVs but everyone else can do 60. My '19 Corolla only sees the 40 part of the sign and turns the indicator red. In a newer model it sounds like you could be driving for an hour with it beeping at you.

I wonder if Toyota have seen a drop in sales along the South West coast of Scotland?

[philip42h]

On 5/4/2024 at 8:58 PM, FROSTYBALLS said:

Legally in the EU/UK the indicated speed shown on a speedometer must never be less than the actual speed, i.e. it should not be possible to inadvertently speed because of an incorrect speedometer reading. The indicated speed must not be more than 110 percent of the true speed plus 4 km/h (2.5 mph) at specified test speeds.

Additionally in the UK, the indicated speed must not be more than 110 percent of the true speed plus at all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

For example, if the vehicle is actually traveling at 50 mph, the speedometer must not show more than 61.25 mph or less than 50 mph.

The GPS indicated speed is an average over a given number of points.

As Mike says, the speed shown on a speedometer is conservative by design. But it would be a mistake to assume that GPS derived speed is accurate / exact. It is calculated from the rate of change of GPS calculated position so reasonably good at a constant speed on a straight and level road - it is unlikely to be out by more than 2% under those conditions. It is significantly worse around curves, on gradients and under acceleration or braking - though such errors are short term and tend to be averaged out. But if we get to a GPS indicated speed above 98% of the speed limit, we risk being over.

The speedometer on the other hand measures speed on the rate of revolutions of the road wheels and an assumed circumference of the road wheels:

• There's a variation of about 2% between a new and barely legal tyre.
• There's a variation of about 3% between the different OEM wheel and tyre sizes fitted to a RAV4.5 - though we tend to stick with the one we were given.
• There will be differences between different makes of tyre (sidewall stiffness etc.) and the temperature / pressure - probably another percent or two.

Such variations may, of course, cancel out, but if additive could easily account for a 5% difference in indicated speed between one RAV and another ...

[SDR]

Having made clear (above) that I routinely either turn off RSA altogether (short journeys) or switch the overspeed warnings to visual only (longer journeys), I probably ought to say that I don't deliberately drive over the limit and I wouldn't mind the overspeed warnings if the system was always correct;   but it very much is not.

According to the manual, the system uses a mix of data from the front camera and also from the in-built mapping.   IIRC, it doesn't say which is prioritised in the event of conflicting data.

In the short time that I have had the Corolla I have seen all sorts of wild and wacky speed limits displayed.    Some appear to come from side/slip roads or exits not taken on roundabouts, some when a speed sign is obscured by vegetation, the camera picks up the '20' signs outside schools that only apply when the signs are flashing, etc., etc., ad nauseam.

So if I didn't kill the overspeed beeping it would be going off way too often.   I don't want to have this happening and either drown it out with music or ignore it because, just maybe, something might be beeping that I really do want to know about.

[AndrueC]

I agree. It's unusual for me to drive over the limit and if I do it's only by 1mph or so. I'm almost religious at sticking to the posted limit. So if it was accurate it would rarely bother me and the times would be so infrequent that I'd probably welcome it.

[SDR]

In all the bumf I've read on the Corolla I seem to remember seeing something to effect that, in the latest facelift version (2023 maybe?), the front camera now has a wider view than before.   Intended, I believe, to enhance the pre-collision system.

I am wondering if an unintended consequence is that the camera is now more prone to picking up road signs that don't actually apply to the route being driven.   Not that would help with defective/obscured signs or those that only apply in limited circumstances (e.g. the limits outside schools that apply when the lights are flashing).

[Roy124]

While GPS may be inaccurate on hills and bends speed cameras tend to be on straight stretches with clear line of sight.

Where we do speed watch there are bends and hills but we still have line of sight 300m inside the zone. 

We can spot the speeders when the bonnet drops and the engine note changes. 

BTW, I can't think of Toyotas we spot with BMW and Audi being most noticeable. 

[Rav Rob]

I have a cunning plan, Photoshop a small photo of a road with a speed limit sign in it showing 100 and tape it in front of the camera, then it will think your permanently under the current limit and leave you alone.

[Cyker]

6 hours ago, SDR said:

In all the bumf I've read on the Corolla I seem to remember seeing something to effect that, in the latest facelift version (2023 maybe?), the front camera now has a wider view than before.   Intended, I believe, to enhance the pre-collision system.

I am wondering if an unintended consequence is that the camera is now more prone to picking up road signs that don't actually apply to the route being driven.   Not that would help with defective/obscured signs or those that only apply in limited circumstances (e.g. the limits outside schools that apply when the lights are flashing).

TBH my pre-facelift Mk4 Yaris already has this problem in spades - It somehow sees every 20mph sign in every side road but misses the sun-bleached corroded mini 40mph signs so it's almost permanently telling me the limit is 20mph on that stretch of the A406, when it is in fact a 40mph road!

And to compound the problem, half the time it thinks the limit is 20 *kph*

This is one of the big things that has put me off getting the new 130HP Premium spec Mk4 Yaris, as that would drive me insane if it was beeping the whole time thinking I'm doing 40mph in a 20kph zone!

 

[SDR]

I've been rattling on about this quite a bit, probably too much and boring folk to death.   However... the debate that I have been having with myself is whether to turn off RSA altogether or go into the sub-menu and change the warnings to visual only.   I am moving towards turning it off altogether (which is quicker anyway!).

Yesterday I was driving on a long, straight road that is subject to a 30 limit and signed as such.   The RSA showed 40 for the length of the road (no repeater signs in 30s).   This is the opposite problem to the annoying bleeps.   I know the road, I know where the fixed speed camera is and I know where the mobile camera vans park (it's a 'hotspot').   Point is, the road looks as if it could be a 40 and, if I didn't know it/had missed the signs/had trusted the RSA display, I could easily have won a speeding ticket. 

Misinformation is worse than no information. 

[SDR]

12 hours ago, Cyker said:

This is one of the big things that has put me off getting the new 130HP Premium spec Mk4 Yaris, as that would drive me insane if it was beeping the whole time thinking I'm doing 40mph in a 20kph zone!

 

I am not saying that it isn't a pain but, assuming that the new Yaris has a similar setup to the Corolla, you can switch the beeps off fairly quickly before driving (switching RSA off altogether is even quicker).

It's now as much of my routine as putting on the seat belt.

[DavidinDerbyshire]

I took delivery of our new Rav 4 GR Sport on Friday and have spent a fruitless and frustrating weekend trying to silence the donging warning that I am speeding.  In fact I am not speeding. It's a well known fact that most cars and Toyota in particular are built with a 10 per cent optimistic speedo so after many years of driving at 33 or 44 or 55 indicated speed I know I am not actually doing that speed but am legally at the limit. However, due to an EC rule, apparently, I now get triple dongs every time I go over the indicated 30, 40, 50 whatever.  It IS possible to silence it by turning off the road traffic sign reader but that is several pushes of a button and every time the engine is shut down it defaults to ON. It's the same with LTS and bleeping from that. It can be cancelled with a long push of the LTA button but it is really annoying. Vertu Toyota say it would be against the law to tamper with it.  But I bet soon, someone, somewhere will fix a workaround. Bring it on !    In all other respects the car is brilliant....in spite of the hefty expensive car tax penalty. Had  it four days now and still haven't heard the petrol engine. But in common with others the British Gas/Hive is proving to be less than attractive. I face a possible 8 week wait....and I suspect the "free" installation will come with a big additional bill for the 25 metres of cabling I require from the meter cupboard to the car port. 

[Parts-King]

Doesn't matter what you buy new, it will be the same, all these things are a legal requirement and can be turned off/down, but will default to ON when you start the car next time, annoying? Yes, but still a legal requirement unfortunately, there are plenty of threads on the same topic on here

[philip42h]

33 minutes ago, DavidinDerbyshire said:

It's a well known fact that most cars and Toyota in particular are built with a 10 per cent optimistic speedo so after many years of driving at 33 or 44 or 55 indicated speed I know I am not actually doing that speed but am legally at the limit.

It is a well-known fact, but it is not actually true ... 😉 Mine overstates the true speed by about 5% so if I were to drive "at 33 or 44 or 55 indicated speed" I would be exceeding the limit.

Whereas, if I stick to the indicated speed, I can be pretty confident that I am within the limit, and it really doesn't cost me that much time.

Excessive 'bongs' are (would be) irritating though ... but that is, in part, the point! 😉 

[FROSTYBALLS]

59 minutes ago, DavidinDerbyshire said:

It's a well known fact that most cars and Toyota in particular are built with a 10 per cent optimistic speedo so after many years of driving at 33 or 44 or 55 indicated speed I know I am not actually doing that speed but am legally at the limit.

In the EU, the indicated speed must never be less than the actual speed, and the indicated speed must not be more than 110 percent of the true speed plus 4 km/h (2.5 mph) at specified test speeds. 

The UK has slightly different requirements in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

There is no blanket 10% over-reading, but a requirement that a speedometer over-reads by no more than 10% plus the added stipulation for given speed ranges.

Government are also looking at how these safety systems may be incorporated into the MOT test in the near(?) future.

[Roy124]

1 hour ago, DavidinDerbyshire said:

 However, due to an EC rule, apparently, I now get triple dongs every time I go over the indicated 30, 40, 50 whatever.

Only 3 dongs, I can live with that.  I was worried it would keep donging like the seat belt warning.

I get an alert now when the signs are misread.   

Otherwise you just need to remember the speed limit sign is the 'do not exceed speed' at the sign.  It is not the point at which you start to slow down.

Similarly it is also the point at which you may start to accelerate after you pass and not when you can see it.

[Roy124]

1 hour ago, FROSTYBALLS said:

The UK has slightly different requirements in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

Just test my maths please.

At 70 on the gauge I can actually be travelling at 63mph.  How dies the 6.25 fit in?

 

[Willss]

My auris is at 30mph when speedo says 33-34mph. My avensis is at 30mph when at 31mph on speedo. Need to remember which car I'm in!

Avensis is most accurate speedo I've ever had. I use the limiter in it set at 31mph (so 30mph). May annoy some people but know I'm not going to get a ticket and only costs me a few seconds in each village I go through! 

[Roy124]

Will, my Corolla was 10%.  With the Yaris Cross,  using the reactive signs, I get about 28-29 for 30-31, around %5.

On the dual carriageway 62-63 set is enough to main speed with the lorries.  Might need to tweak to 64-65 for the Hell Drivers.

[FROSTYBALLS]

53 minutes ago, Roy124 said:

At 70 on the gauge I can actually be travelling at 63mph.  How dies the 6.25 fit in?

The true speed could be 56/57mph (70 -10% - 6.25).

[philip42h]

45 minutes ago, Roy124 said:

1 hour ago, FROSTYBALLS said:

The UK has slightly different requirements in specifying that for all actual speeds between 25 mph and 70 mph (or the vehicles' maximum speed if it is lower than this), the indicated speed must not exceed 110% of the actual speed, plus 6.25 mph.

Just test my maths please.

At 70 on the gauge I can actually be travelling at 63mph.  How does the 6.25 fit in?

The maths doesn't help much ...

Legally, at an actual 70 mph on the road, the speedometer is allowed to read any value from 70 mph up to 83 mph.

Conversely, at an indicated 70 mph, the car can be travelling anywhere between 58 mph and 70 mph.

And we can't know exactly how accurate the speedometer is without comparing it to a reference speedometer (e.g. GPS speed) or measuring the time over a known distance. We can't assume anything other than the fact that if we accept the guidance of the speedometer we will remain within the limit. Practically, modern speedometers are a lot more accurate than they are legally required to be.

[FROSTYBALLS]

Even GPS isn't 100% accurate, as it is the average speed over a given number of points. 

[Roy124]

Thanks to you both.   In general practice, in your MY24 car (I know) you will never get the dongs if you do not exceed the stated speed as shown on the speedo.

Also,  given the greater accuracy that seems to be the case, you won't be hugely under the limit. 

[Roy124]

2 minutes ago, FROSTYBALLS said:

Even GPS isn't 100% accurate, as it is the average speed over a given number of points. 

Similarly the VAS gives a spot reading at the same time as your speedometer is not giving a fixed reading. (Only a swivel-eyed loon can read both simultaneously).

[CPN]

47 minutes ago, FROSTYBALLS said:

Even GPS isn't 100% accurate, as it is the average speed over a given number of points. 

Everyone keeps on banging on about this and yes, it's true that it's not 100% accurate (even atomic clocks aren't!) but if your smartphone is locked on to more than 20 satellites (and most phones are capable of that) then it gets pretty darn close to that magical 100%. So, I would suggest that it is the most accurate device available (even on twisty roads) to the average driver for a fix on speed across land. It is far more precise than anything else immediately available for comparison purposes.

[Nick72]

7 hours ago, philip42h said:

It is a well-known fact, but it is not actually true ... 😉 Mine overstates the true speed by about 5% so if I were to drive "at 33 or 44 or 55 indicated speed" I would be exceeding the limit.

Whereas, if I stick to the indicated speed, I can be pretty confident that I am within the limit, and it really doesn't cost me that much time.

Excessive 'bongs' are (would be) irritating though ... but that is, in part, the point! 😉 

Mine doesn't. Calibrated with multiple GNSS receivers on flat and level roadways. It states 77mph on the speedo when it's true speed is 70 to 71mph. 34mph is actually 30mph. So we are talking c. 10% over. Or at least this is the case on my 2021 PHEV.

That's what makes the speed warning thing especially annoying or will be when I need to swap to the GR Sport PHEV in 3 months. It's going to be bong bong bonging when:

A. I'm not actually speeding because the Speedo is reading fast.

B. I'm not actually speeding because the road sign detector is misreading signs, as it consistently does. Like, every single day. Today I had 10mph despite being in a 40mph zone for 10 minutes of driving.

It's especially dumb because the tech isn't there to do it robustly and reliably and because Speedo is set fast.

What manufacturers need to do is put a quick way of setting it to visual warning only for each drive. Conscious decision. One button press. 

Same on the LTA, which I didn't know about. That's like frickin ping pong on the default settings and slow to react on the next sensitivity setting.

🤯