[JoeC]

Since then I've done two 'proper' ones with videos, tests and professional moderators.

It's a real eye opener. From the bloke who, on being presented with the factoid that humans can only fully concentrate for a few minutes at a time before being distracted, argued vehemently with the moderator that when driving his concentration was 100%. ALL THE TIME. He obviously had no sense of irony. And then the woman who, despite being told three times not to use her 'phone perversely kept using it and was thrown out.

[Rob P]

I was told, maybe apocryphally, of a woman who, three hours into such a course answered her phone.

The schoolteachers told her in no uncertain terms that she had been instructed to turn the phone off, at which point she looked baffled and replied "Not speak English"

There's actually no point in engaging, or attempting to point out the flaws in the content; they know it, and reminding them does not earn you any brownie points. Fix your eyes on the screen, look as if you are absorbing it all, and dream of flying. The four, tedious hours soon drag by.

Rob P

[Flyin'Dutch']

Never yet one a SAC although I have clocked several speeding tickets but luckily enough in other jurisdictions where there are no points awarded; some countries are inexpensive for speeding, some very much not so.

[johnm]

Every driver should have to meet IAM standards after 5 years or be restricted to 50 MPH and not allowed on motorways

[PeteSpencer]

At the course I attended recently run by a pompous early 60s male fart: retired driving instructor and a pleasant 30s female who exuded 'teacher' and clearly knew how to hold an audience, I had a bit of a set to with the fart who would not accept that car speedometers over read when compared to satellite information and said that if you set your cruise control at 70mph your car would travel at 70mph. (and pro rata for other speeds).

He told me that satellite speed indications could not be relied on because of terrain and that I did not understand how the satellite navigation system works.

With exemplary self-control, I bit my lip and gave up on him and kept my gob shut.

Peter

Edit for insert of crucial word to emphasis meaning.

[TopCat]

He told me that satellite speed indications could not be relied on because of terrain and that I did not understand how the satellite navigation system works.

My speedo overreads by 4mph at 40, 5 at 50 and about 6 at 70, according to Google Maps when I'm driving at a steady speed.

So I've started to drive at about 5 over, indicated, when conditions permit and the speed limit is 40 or more.

Am I safe from the radar gunners? And the average speed checks?

[PeteSpencer]

Interestingly the speed indicated figure on my Tom Tom , for example doesn't go red from green and start bonging till 73mph reached, so I set my cruise control accordingly.

Sadly the speed limiter on my krauto only sets at 5mph increments, too coarse for accuracy at low speeds.

Peter

[Rob P]

Unusually the V8R speedometer under-reads. The first one ever since I have had the ability to verify it (Other than by word of mouth from nice policemen at the roadside )

Rob P

[TheFarmer]

[Paul_Sengupta]

A pseudonym?

[Sooty25]

As speedos derive their speed from a sensor, either in gearbox, diff or on one of the wheel hubs, and therefore calculate speed based on revolutions and rolling circumference, has anyone calculated the variation in indicated speed between a brand new tyre and the same tyre worn to 1.6mm tread?

[T67M]

I have never driven a UK-spec car with an accurate speedo when compared with GNSS - most over-read by about 5%. I believe the legal requirement in the UK is that the speedo must read within -0/+10%.

I have never driven an American car with an inaccurate Speedo compared to GNSS. I believe the legal requirement in the US is +/-5%.

Those of you familiar with tolerances and engineering practice will immediately understand why with a requirement to be with -0/+10%, just about the least likely thing you will find is an accurate meter. In order to maximise the production yield and reduce the number of units returned as out of tolerance, you design/calibrate the meter to read in the middle of the allowed tolerance range.

[Chris10]

I know someone who apparently turned up to one of these courses late and upon being asked why, he replied "sorry I had to stick to the speed limit". He was chucked out straight away and had to take the three points and fine.

[riverrock]

Its actually +10% +6.25mph:
http://www.legislation.gov.uk/uksi/2001 ... ule/3/made

3. For all true speeds of between 25 mph and 70 mph (or the maximum speed if lower), the difference between the indicated speed and the true speed shall not exceed—

V/10 + 6.25 mph

where V = the true speed of the vehicle in mph.

In this item “maximum speed” has the meaning given in regulation 3(2) of the Construction and Use

[Paul_Sengupta]

has anyone calculated the variation in indicated speed between a brand new tyre and the same tyre worn to 1.6mm tread?

Not calculated, but observed. In my experience it's pretty much un-noticeable, certainly no more than 1mph. Had this recently as I got a new set of tyres on the back of the Jaguar the other day, with the old set almost down to 1.6mm!

My Jaguar reads 77.5mph at 70mph! My BMW reads 73 and my MR2 reads 75.

I have to say, my Jaguar tolerance isn't that unusual given that I sometimes sit for ages behind f-wits not - or barely - overtaking when doing what indicates on my speedometer to be 70mph - actually around 63mph.