Ducati Sporting Club UK > Model Specific - Discussion, Technical Problems and Help > General Motorcycles only > Speed limit tolerances

[philthy]

Originally Posted by ariel

Nice to see that you guys are such paragons of virtue. Don't you ever exceed 60mph when you are out riding on country A roads?
You are absolutely right in saying that we should keep within the 30 mph limit in built up areas but to advocate going no faster than 60 seems incredible coming from motorcyclng enthusiasts.
We live and learn.

I drive for a living. No license no job, it's as simple as that. That and the things I've done and seen over the last 30 odd years of driving / riding do colour my judgement towards excessive speed.

That said, if I'm out on the bike and it's a sunny day I will use my common sense as to whether it's safe to up the pace a bit, but as all of my riding is done in North Wales where 1mph over will get you a ticket, I think it's pointless to go above 60 on a long straight, which is where any camera vans or traffic cops will be.

I'm quite happy for all the fast boys to play racers on the popular routes and keep the cops busy writing tickets so that I can go and play somewhere quieter and twistier.

[Ray]

Originally Posted by Paul James

How can there be no tolerance on a measurement ?

That was the point I was trying to make really. Who determines what 70mph is for instance ? What is the manufacturers tolerance on the speed cameras ? NOTHING is manufactured without a tolerance whether it be 0.0005% or 10% or expressed as something other than a percentage.

What is the manufacturers tolerance on a speedometer ? What effect does using tyres made by different manufacturers have opn speedometer readings?

Does anyone think that applying a strict 70mph limit has any true effect on road deaths and casualties when it usually goes hand in hand with a serious reduction in the police presence on our roads ? Would you rather have someone drive past your kids school gate at 34mph concentrating on the road or someone driving at 29mph writing a text on their mobile phone ?. The former will trigger the speed camera, the latter will run into your kid without even realising they are there !!!

Where the influence of speed on motorcycling road deaths is concerned I think some of you will be utterly amazed at how this myth has been forever smashed when the latest statistics are released locally ;-)))

The "tolerances" for the equipment used are probably available from the mannufacturer or maybe the operators manual, you could maybe try and get hold of the latter under FOI but don't expect them to give in easily!

The ACPO guidelines probabaly allow for the tolerance i.e the reading has to be well over the legal limit so even allowing for the tolerance of the equipment you are definately over the limit when nicked.

The no tolerance stasi have conveniently forgotten about this so there is a possibility that you can get done while still being under the limit and thats not taking operator error into acount. There are various individuals questioning the accuracy of various speed measuring devices used by talivan/scamera partnerships. A quick look round pepipoo has more info.

MCN had been digging about asking if equipment had been specifically tested on bikes, that seem to produce a mixed response form the various bodies questioned and a yes-no interlude.

Bike are difficult to "acquire" using some equipment............so never ride in a straight line

Ray.

[ariel]

I am convinced that the emplacement of so many speed cameras does not add to road safety one iota.
There is a valid argument for controlling speed in busy dangerous built up areas. This has always been the case and obviously always will be.
The business of the so called "Camera partnership" is to site cameras regardless of their efficacy in preventing deaths.
There is a move afoot to lower speed limits even further on our country roads.
These limits are already lower than they were in the 1950's when tyres and brakes were much less efficient.
What would add to road safety is more driver training and safer road surfaces.

[psychlist]

Car/Bike speedo's have to read within a band of -10% to +0% so, if your speedo says you're doing 70mph, then you could actually be doing anything from 70 down to 63mph. I had my bike's speedo "compared" with a guy I know who's speedo is "calibrated" for his work (ahem) and it was spot on at an indicated 70mph but I needed to be doing an indicated 33mph to be doing an actual 30! That was on well worn Diablo's. I did a simple check with him again when I had new tyres fitted and it was spot on all the way from 20mph up to 70. This is because a new tyre has a larger rolling circumference than a worn one and centrifugal force has a greater effect on a worn tyre than a new one (obvious when you think about it) so you travel further for each turn of the wheel/engine. If a motorcycle is heavily banked over round a fast corner then you'll be using a smaller diameter part of the tyre and the rolling circumference will be greatly reduced so you'll actually be going LOTS slower than your speedo may indicate!
From my limited experience it seems that stabilised radar/laser targetting devices in the hands of a trained operative are generally regarded as "absolute" measuring devices and it is up to the operator to use their judgement on the spot regarding the prevailing conditions to determine the actual course of events once a certain speed is indicated on the recording instrument, using the (very old, and some say out of touch with modern technology) ACPO guidelines as a yardstick, so you may get away with 79mph in some 70 limits and get done for much less in others.
Not that I know anything about the subject of course

[Paul James]

Originally Posted by psychlist

Car/Bike speedo's have to read within a band of -10% to +0% so, if your speedo says you're doing 70mph, then you could actually be doing anything from 70 to 77 mph. I had my bike's speedo "compared" with a guy I know who's speedo is "calibrated" for his work (ahem) and it was spot on at an indicated 70mph but I needed to be doing an indicated 33mph to be doing an actual 30! That was on well worn Diablo's. I did a simple check with him again when I had new tyres fitted and it was spot on all the way from 20mph up to 70. This is because a new tyre has a larger rolling circumference than a worn one and centrifugal force has a greater effect on a worn tyre than a new one (obvious when you think about it) so you travel further for each turn of the wheel/engine. If a motorcycle is heavily banked over round a fast corner then you'll be using a smaller diameter part of the tyre and the rolling circumference will be greatly reduced so you'll actually be going LOTS slower than your speedo may indicate!
From my limited experience it seems that stabilised radar/laser targetting devices in the hands of a trained operative are generally regarded as "absolute" measuring devices and it is up to the operator to use their judgement on the spot regarding the prevailing conditions to determine the actual course of events once a certain speed is indicated on the recording instrument, using the (very old, and some say out of touch with modern technology) ACPO guidelines as a yardstick, so you may get away with 79mph in some 70 limits and get done for much less in others.
Not that I know anything about the subject of course

Shouldn't that read "63 to 70 mph" Paul ?

My biggest concern is that there is no natinally agreed binding tolerance on the actual speed relative to the measuring equipment. It isn't just or reasonable for one police authority to apply "zero tolerance" speed enforcement while others apply the 10% + 2mph rule. The speed limits are national, so should the enforcement levels be, surely ?.

[Rushjob]

Question came up as a guy who does regular van deliveries to us recently got a ticket for doing 76 in a 70 zone, if the 10% plus 2mph was applied he shouldn't have been nicked.

Paul, you mention the guy driving a van getting done for 76 in a 70.....
If said van was anything bigger than, say, a Peugeot Partner or Transit Connect ( more than 2T gross ) and he was on a dual carriageway ( not motorway ) then his max speed in that vehicle would be 60mph so he would have been well over 10% + 2 ......... it's suprising how many drivers don't know the limits applied to the vehicles they drive

[MJS]

Originally Posted by Paul James

Shouldn't that read "63 to 70 mph" Paul ?

My biggest concern is that there is no natinally agreed binding tolerance on the actual speed relative to the measuring equipment. It isn't just or reasonable for one police authority to apply "zero tolerance" speed enforcement while others apply the 10% + 2mph rule. The speed limits are national, so should the enforcement levels be, surely ?.

Surely, the answer is the speed limit is the speed limit, and getting away with anything over that is a bonus?

At the end of the day, if it was written down that it's speed limit plus 10% plus 2mph, then the speed limit on a motorway or dual carriageway would in effect be 79mph...

[psychlist]

Originally Posted by Paul James

Shouldn't that read "63 to 70 mph" Paul ?

Yes, if the speedo tolerance is -10% to +0% then at an actual 70mph it would be reading about 77, when it reads 70 then you could be going as slow as 63
So, if the speedo is within tolerance, then you'd potentially have to be breaking the limit by only a few mph for it to be saying, say 80mph

[Paul James]

Originally Posted by psychlist

Yes, if the speedo tolerance is -10% to +0% then at an actual 70mph it would be reading about 77, when it reads 70 then you could be going as slow as 63
So, if the speedo is within tolerance, then you'd potentially have to be breaking the limit by only a few mph for it to be saying, say 80mph

Yup, what I thought you meant, makes sense for it to work that way I guess

Still think there should be a national tolerance stated for all drivers (take your point about the vehicle types Rushjob).

Static speed cameras are biased in favour of lorries as if set to go off at the limit that applies to cars in 70 zones they can be way over their legal limit before tripping the camera. Surprised nobody has taken that one up at the European Court of Civil Liberties yet ;-)))

[Glyn]

i think they can tell the difference between a car and a lorry