Speedo Inaccurate

[Corey_R]

You're right, this isn't the right place to be discussing it since it is an industry wide regulation and it also goes beyond Australia.

The reason that your examples are not the same is because deflating your tyres poses handling and safety issues and changes the performance of your car in non-consistent ways. Mono instead of stereo also changes your listening experience.

Having a speedo which is consistently a certain % faster does not pose any safety reduction (in fact the opposite) or a reduction in functionality or lessens the experience of driving the car. So the examples really aren't the same.

And as discussed a million times already Since the speedo IS entirely consistent if you really need to be driving at the absolute speed limit, then I'm sure you're intelligent enough to figure it out the maths in your head

[Beaker]

We'll have to agree to disagree and concentrate on the important stuff ( ) I think.

[Corey_R]

Sounds good

[Idle]

People need to step back and CHILL and think about the 'big picture' and not just themselves to understand what is happening here.

They are such stupid examples. A speedo which shows 100kph when you're doing 93kph isn't taking away any functionality or impeding your ability to drive. Grow up!

Actually, my speedo shows 100 when I'm doing 92 — and the last time I looked I was pretty grown up (I'm 85), and no, it doesn't take away any functionality from the car itself (as to my ability to drive, that's a moot point — lots of younger drivers say people my age shouldn't be out in anything faster than a wheelchair...), but if I travel at that speed in the left lane of a busy highway I often find myself being tailgated and 'encouraged' to speed up.

As to the 'big picture', what we now have are mandated speed limits that (here in Victoria, at least), are to be rigidly observed almost at pain of death, and electronic speed measuring devices that are (or are legally deemed to be, which may not be the same thing) greatly more accurate than the 'made down to a price, not up to a standard' units fitted to the vehicles we drive.

That's what's wrong — the 'near enough is good enough' approach by manufacturers that's not merely tolerated, but (in the interest of State revenue? — we regularly see income from fines included in annual budgets) even legislated for.

And to say that it's always been so is missing the point — with few exceptions, speedo's and other automotive instruments have traditionally been cheap devices that made a 'near enough' guess, but the legislation governing the speeds we travel at and the harsh enforcement thereof has not always been as it is today.

Right back to horse and buggy days there have been speed and traffic management rules in built-up areas — as indeed there need to be, albeit that today some of these can only be described as paranoid... but on the open road you were once expected to drive in a manner that was within your vehicle's (and your own) safety range. Most people did so, and income from traffic fines was trivial.

This reads like a rant — maybe it is... but I'm quite sure speed measuring devices in cars and trucks can be made to be accurate and believable. With the technology available today, they need no longer be triggered from any rotating/wearing part of the vehicle itself.

[Maverick]

As to the 'big picture', what we now have are mandated speed limits that (here in Victoria, at least), are to be rigidly observed almost at pain of death, and electronic speed measuring devices that are (or are legally deemed to be, which may not be the same thing) greatly more accurate than the 'made down to a price, not up to a standard' units fitted to the vehicles we drive.

That's what's wrong — the 'near enough is good enough' approach by manufacturers that's not merely tolerated, but (in the interest of State revenue? — we regularly see income from fines included in annual budgets) even legislated for.

The UN standards adopted by our country in our ADR's means that you speedo cannot display a lower speed than you are traveling at.

The previous ADR's allowed + or - 10%.

And to say that it's always been so is missing the point — with few exceptions, speedo's and other automotive instruments have traditionally been cheap devices that made a 'near enough' guess, but the legislation governing the speeds we travel at and the harsh enforcement thereof has not always been as it is today.

The new regulations means you can't get done for speeding if you're looking at the speedo.

This reads like a rant — maybe it is... but I'm quite sure speed measuring devices in cars and trucks can be made to be accurate and believable. With the technology available today, they need no longer be triggered from any rotating/wearing part of the vehicle itself.

There isn't any technology now that can give you a reliable indicator of your speed without using a rotating/wearing part like the tyres. The GPS system is not really suitable for use as in tunnels, cuttings, mountainous areas and so on it will suffer from error or not work at all.

I don't really see any major problems with the current system which works with a known amount of error.

[KWICKS]

The new regulations means you can't get done for speeding if you're looking at the speedo.

Only crashing becasue you had your eyes off the road fearing speed cameras...

[Corey_R]

I read your post Idle, and whilst you first appear to be arguing against me, your 'rant' basically just gives all the justification that's needed for the car manufacturers to be doing what they are being mandated by ADR's to do. And Maverick clarified all that needed to be, so

@KWICKS - no not at all. You only need to do that with OLD cars which DON'T have this '(7)% tolerance' like the VW cars do. That's yet another reason for this situation

[Idle]

There isn't any technology now that can give you a reliable indicator of your speed without using a rotating/wearing part like the tyres. The GPS system is not really suitable for use as in tunnels, cuttings, mountainous areas and so on it will suffer from error or not work at all.

I don't really see any major problems with the current system which works with a known amount of error.

That's just the point — it isn't a known amount of error, it varies between vehicle makers and between individual instruments — even by the viewing angle of the driver.

And there are non-rotating methods of measuring speed, varying from very cheap (your 'laser' computer mouse, for example, that can be made for a dollar or so, is surprisingly accurate, works on pretty much any surface and uses technology that could easily be scaled up to what's required for road vehicles if the demand were there) to the generally detested speed cameras now in world-wide use.

Even the focusing sensor systems of modern digital cameras could probably be adapted without too much trouble, and I don't doubt there are others I've not even heard of.

Meanwhile, I suppose, I'll continue either feeling nervous when I exceed the indicated speed or tolerate having it made clear that I'm getting in the way of progress when I don't.

Incidentally, in Victoria we have an advertising campaign called "Wipe Off 5" — if you add that to the inbuilt 5 to 10% error... (how slow can you go?)

I think I've now had a bit more than my 2c worth — maybe 5c?

[Topend]

I'm glad to see I am not the only one that believes the notion of an error built into the speedo in order to protect drivers from themselves is silly.

Lets now apply this to aircraft so pilots don't exceed their Vne (never exceed speed). Makes no sense there either.

A GPS is not the only give away to the speedo being inaccurate. Other traffic whizzing past is another and in my case my wife accusing me of speeding when I went past her in my Landcruiser.

A few have admitted to calculating in their head the corrected indicated speedo reading to be driving to be at the true speed limit. If this is happening, and I am doing this too, what is the point of the error?

Dave.

[Beaker]

The previous ADR's allowed + or - 10%.

The ADRs always stated that it could never over-read (ie you could not be traveling faster then what was indicated, that bit remains, the only difference is now an additional mandated +4km/h difference between road speed and indicated speed.

As far as I can work out (maths isn't my strong suit) technicaly you could have a 10% error + 4km/h ie at 100km/h (road speed) your speedo could be indicating 114km/h and still be within the ADR.

Topend, its no longer about being able to make something that accurate - A terratrip in a rally car is accurate to meters over 100s of km and remains that accurate even though the tyres have a much larger change in diameter (due to far greater tread depth) then a road car. Fitting larger wheels is simply accounted for by adjusting the calculation from whatever sensor is sending the road speed. The same would be simple to apply to road cars

Its got nothing to do with the accuracy of the hardware and everything to do with policy.