Speed camera query about the different types

Mr.Generous

user1977 said:

ontheroad1970 said:

user1977 said:

Try out Google Maps or one of the other satnavs which give your GPS-derived speed - that's (on the whole) going to be more accurate than your speedo. My last car displayed 33 when actual speed was 30, 74 when 70, etc.

At least the speedometer will be consistently slightly inaccurate.  I would never rely on a GPS based speed.  

It's always been consistent whenever I've tried it.

As tyres wear the speedo will read higher than actual road speed. With full tread probably overstates by a minimum of 2mph at 50, fully worn maybe 4mph over. At speeds over 100 speedo can be much more optomistic. Car magazines sometimes show what the speedo read v's radar check and as previously said they never under read.

[Deleted User]

It's a bit of both. Speedometers always read a bit high, to avoid reading low which is illegal. 10% is not uncommon.

Those signs are not very accurate either. They don't need to be because they are just for indication, not for any legal use. Not that the ones used in court are particularly accurate either.

If you want to know your true speed, use your phone. Get a GPS speedo app.

Brie

@baser999 et al
No different size wheels fitted. 

I don't purposely drive excessively over the speed limit but there are spots where it suddenly drops from 40 or 50 to 30 and I only know that because I've driven that way before because the actual signs are obscured by foliage.  So I take my foot off the accelerator in anticipation to slow to the correct speed as putting on the brakes would mean the idiot on my back bumper (who probably doesn't know the speed has changed) would end up sitting beside me.  I so tap my brakes sometimes if someone's too close.  And of course the camera van is usually just around the corner out of sight hoping to catch out the idiots at which point they slam on their brakes.  

As for checking my GPS - a chance would be a fine thing!!  Not an extra in a basic up.  And zizzing usually consists of getting the hamsters to gallop a bit harder!!!

Petriix

TooManyPoints said:

I'm not worried about a ticket as I think even if I was correctly doing 33 I am within the variation limit. 

There is no such thing as "the variation limit." What you are probably referring to is the National Police Chiefs' Council's guidance on speeding enforcement. This suggests that speeding should not normally see action under (Limit + 10% + 2mph) - so 35mph in a 30mph limit. The guidance document is here:

Microsoft Word - Speed Enforcement Guidance ACPO_2011 2015_May 2013_Internet (college.police.uk)

you will note that it is guidance, not the law and that it does not replace an individual officer's discretion.

Yet, as far as I am aware, no one has ever posted a NIP showing a speed lower than the 10% +2 guideline. I've seen some people claim to have been fined under that speed, but they're never able to substantiate it. 

user1977

Brie said:

As for checking my GPS - a chance would be a fine thing!!  Not an extra in a basic up.

Nobody said it had to be factory-fitted - or even fitted at all. Use your phone.

Brie

user1977 said:

Brie said:

As for checking my GPS - a chance would be a fine thing!!  Not an extra in a basic up.

Nobody said it had to be factory-fitted - or even fitted at all. Use your phone.

my phone doesn't have a gps either and I don't think the capacity to add one.  But thanks for the thought.  Maybe when I buy my next phone in 10 years time!!!

TooManyPoints

Yet, as far as I am aware, no one has ever posted a NIP showing a speed lower than the 10% +2 guideline. I've seen some people claim to have been fined under that speed, but they're never able to substantiate it.

Quite correct.

Steve182

A friend, who religiously obeys speed limits told me that one of those roadside "are you speeding?" thingies once told him he was doing about 5mph less than his speedo in a 30 zone, convincing him that his speedo was out by 5mph. Couple of days later he was done by a camera for 35mph in a 30!

GPS based speed is normally very accurate except when there are hills. I know that my speedo is about 2mph over at 50 to 70mph from multiple tests VS a GPS app on the phone, so I can comfortably set cruise control at just over the speed limit in the knowledge that I'll not get a ticket.