Speed limits speedometers vs GPS speed

[sixor8]

FiF said:

Absolutely this is the simplest and quickest way to sort it. The GPS engines in phones and the like aren't up to providing proper speed data logging in anything other than the simplest situation, but as described above, straight flat road and checking the difference at various steady speeds is for most people quite sufficient to produce a correction chart across the typical range.

Thankfully no longer have to mess about finding the official measured miles.

Back in the day.... And I mean before even cell phones, I had a method to check your speedometer.

The markers at the side of the motorway are 100m apart. If you hold a steady speed as indicated, and time the distance to pass 10 of them, i.e. 1km, dividing that time into 3600 gives your speed in km/hr. I used to do this with every change of car throughout the 80s and 90s, most over-read by only a few mph, as experienced. The worst was a Cavalier 2.0 GL, it indicated 80mph at a steady 70mph! I suspected it had been apart.

[ATG]

Phone GPS works fine when driving a car at close to the speed limit. Just do the experiment for yourself. It works. The idea that the slight lag is an issue is baloney unless you drive in such a way that you arrive at your target speed with a massive jerk (jerk being rate of change of acceleration) and no normal person does that

Our crappy VW Transporter's speedo is utterly hopeless. Wags like a teacher's finger at up to 40mph and then settles to a smooth and massively exaggerated reading thereafter. Our Hilux's speedo is currently completely dead. So I use my phone in both. Just to make sure it was indeed sufficiently accurate I also used it in our other cars, and, completely unsurprisingly, it was fine.

[agtlaw]

ATG said:

Was that decision based on the prosecution's evidence being unreliable rather than a happy consensus being achieved that he was indeed speeding, but not by much?

The decision on Westlaw is lacking detail. I suspect the charge particulars (cf. the Statement of Offence) included the speed and the defendant introduced some doubt about the speed. In which case, the police should have been more careful when drafting the charge.

[rdjohn]

Derek Smith said:

There is no 'rule' with regards the threshold for prosecution for speeding. ACPO, as was, issued guidelines.

I was prosecutions inspector in my force and we used it as a rule as long as there were no aggravating factors. In other words, if an officer wanted to prosecute a driver at a speed lower than the advised limit, they had to produce reasons. In the 2 years or so I was a prosecutions inspector, I can remember two instances, both instigated by traffic officers - one of which was when the errant driver overtook a police car at over the limit, the other when the driver would not accept she was over the limit - and both went through to CPS. They came back to me both times and I justified the limit. There may have been more as memory fades. I can't 'produce paperwork' to support, but even if I could, I wouldn't. If you don't want to believe me, then by all means don't. Believe your own fairly stories.

I have had no acquaintance, relative or friend who has told me they have been prosecuted for a speed under the guidelines.

I had an uncle who held a similar position during the 60s. As my dad and other uncles acquired their first cars in the early 60s he used to lecture them that speedos were notoriously inaccurate and that their Police cars had “specially calibrated speedos”, but they would give motorists an allowance of 10% to be fair.

At that time, I think that following a car was the only way to catch someone and I think they had to do it for 1/4 mile. It may have also needed a driver and observer for corroboration to be successful. A lone driver would just give you a warning unless there was something else - defective light etc. By the late 60s the Borough had a huge radar that sat on the back shelf of a Cortina estate car and the operator could radio the speed of a car ahead to another waiting officer. VASCAR made life much simpler for the lone Police officer.

Despite the switch from cable driven to digital speedos, I guess that the 10% allowance +2mph has become stuck at this rather generous level.

[FiF]

1

sixor8 said:

FiF said:

Absolutely this is the simplest and quickest way to sort it. The GPS engines in phones and the like aren't up to providing proper speed data logging in anything other than the simplest situation, but as described above, straight flat road and checking the difference at various steady speeds is for most people quite sufficient to produce a correction chart across the typical range.

Thankfully no longer have to mess about finding the official measured miles.

Back in the day.... And I mean before even cell phones, I had a method to check your speedometer.

The markers at the side of the motorway are 100m apart. If you hold a steady speed as indicated, and time the distance to pass 10 of them, i.e. 1km, dividing that time into 3600 gives your speed in km/hr. I used to do this with every change of car throughout the 80s and 90s, most over-read by only a few mph, as experienced. The worst was a Cavalier 2.0 GL, it indicated 80mph at a steady 70mph! I suspected it had been apart.

Not that far back in the day there used to be mile markers on the motorway near the junction closest to the RPU base so that a check could be done at beginning end of shift. M5 jn 6 was one such, northbound, southbound and even on the stretch from Claines Island to J6. Tbh never taken the trouble to see if they're maintained these days. M1 jn 29 another. Once you'd been told where the markers and section were sitting then was easy to spot them.

Mentioned before one rule of thumb re prosecution limits used to be PL+10%+10mph. 10% to allow for measurement errors, the additional 10mph to cater for the notion that the driver should have known they were OPL provided actually paying attention.

[Craig_suke]

ATG said:

Craig_suke said:

E-bmw said:

Why is it that so many people on here get all hung up on whether anyone did or didn't get a ticket for doing under or over the "guidelines" stated?

I personally couldn't give 2 sh!ts what speed anyone did or didn't get done for or whether it is concocted or not, and I certainly couldn't be bothered with giving the claimant any grief or need for proof.

If it happened it happened, if it didn't it didn't what is the point in arguing the point?

Build a bridge & get over it.

Personally find it’s funny that people will try to pass around false information, these people need to be called out about it

I’ll put it out there that no forces ticket office (the ones who would issue the ticket or offer a course) would accept a ticket for less than their own stated guidelines as it would be an easy argument in court. The officers, camera’s and vans all operate to these guidelines.

As mentioned many times people claim it to get some attention but then could strangely prove it.

You think "I wasn't breaking the law enough to be prosecuted" is a defence? Interesting.

Where do i say that? Read again (probably help to slow down whilst doing so)

Spoiler alert (It would probably be the not following the guidelines bit )

[ATG]

Craig_suke said:

ATG said:

Craig_suke said:

E-bmw said:

Why is it that so many people on here get all hung up on whether anyone did or didn't get a ticket for doing under or over the "guidelines" stated?

I personally couldn't give 2 sh!ts what speed anyone did or didn't get done for or whether it is concocted or not, and I certainly couldn't be bothered with giving the claimant any grief or need for proof.

If it happened it happened, if it didn't it didn't what is the point in arguing the point?

Build a bridge & get over it.

Personally find it’s funny that people will try to pass around false information, these people need to be called out about it

I’ll put it out there that no forces ticket office (the ones who would issue the ticket or offer a course) would accept a ticket for less than their own stated guidelines as it would be an easy argument in court. The officers, camera’s and vans all operate to these guidelines.

As mentioned many times people claim it to get some attention but then could strangely prove it.

You think "I wasn't breaking the law enough to be prosecuted" is a defence? Interesting.

Where do i say that? Read again (probably help to slow down whilst doing so)

Spoiler alert (It would probably be the not following the guidelines bit )

To quote you, "it would be an easy argument in court". It's in the middle of your second paragraph.

[Derek Smith]

rdjohn said:

I had an uncle who held a similar position during the 60s. As my dad and other uncles acquired their first cars in the early 60s he used to lecture them that speedos were notoriously inaccurate and that their Police cars had “specially calibrated speedos”, but they would give motorists an allowance of 10% to be fair.

At that time, I think that following a car was the only way to catch someone and I think they had to do it for 1/4 mile. It may have also needed a driver and observer for corroboration to be successful. A lone driver would just give you a warning unless there was something else - defective light etc. By the late 60s the Borough had a huge radar that sat on the back shelf of a Cortina estate car and the operator could radio the speed of a car ahead to another waiting officer. VASCAR made life much simpler for the lone Police officer.

Despite the switch from cable driven to digital speedos, I guess that the 10% allowance +2mph has become stuck at this rather generous level.

The 10mph +3mph was often ignored by reporting officers. They, presumably, made judgements based on the standard of driving and attitude. Dick Brunstrom, ex my old force, was i/c ACPO. He went on to be CC North Wales and created havoc for the British Rally. Strange man. He was very closed with regards to speeding being the major cause of death on the road, despite evidence to the contrary, and speed traps to be effective in reducing speeding, which is rather contentious. He then pushed for legalising certain controlled drugs, suggesting they were less dangerous than over-the-counter drugs (a bit iffy) without mentioning alcohol and the most dangerous drug in common use (lots of stats). Lots of backlash if I remember, I suspected he spouted such things because he loved publicity and his name in the press. He screwed his own HQ at one time. Why? If concerned about security, there were more effective ways of going about it that opting for publicity. There was a big fuss about a photo he used in a publication of a casualty with his head severed. Arrogant showing that without the NOK's permission I reckon.

There was a lot of resistance to his 10% +3 guidelines, but in all honesty, it wasn't such a great difference. As I said, I knew of only two cases in two years in my prosecutions area where officers asked for prosecutions below Brunstrom's line. I supported both.

[BossHogg]

dundarach said:

Because I now drive a Cashcow, I just stick at the speedo reading, happy in the knowledge I'll be slightly under.

Stick cruise on and relax.

My old Honda Civic reads under by 4-5 mph, saved my bacon a few times.

[Craig_suke]

ATG said:

Craig_suke said:

ATG said:

Craig_suke said:

E-bmw said:

Why is it that so many people on here get all hung up on whether anyone did or didn't get a ticket for doing under or over the "guidelines" stated?

I personally couldn't give 2 sh!ts what speed anyone did or didn't get done for or whether it is concocted or not, and I certainly couldn't be bothered with giving the claimant any grief or need for proof.

If it happened it happened, if it didn't it didn't what is the point in arguing the point?

Build a bridge & get over it.

Personally find it’s funny that people will try to pass around false information, these people need to be called out about it

I’ll put it out there that no forces ticket office (the ones who would issue the ticket or offer a course) would accept a ticket for less than their own stated guidelines as it would be an easy argument in court. The officers, camera’s and vans all operate to these guidelines.

As mentioned many times people claim it to get some attention but then could strangely prove it.

You think "I wasn't breaking the law enough to be prosecuted" is a defence? Interesting.

Where do i say that? Read again (probably help to slow down whilst doing so)

Spoiler alert (It would probably be the not following the guidelines bit )

To quote you, "it would be an easy argument in court". It's in the middle of your second paragraph.

Well done you’re Almost there, To argue the staff/officer wasn't following guidelines.