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  • FIRST POST
    • samba987
    • By samba987 7th Feb 18, 2:49 PM
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    samba987
    Failed driving test as sat nav speed incorrect.
    • #1
    • 7th Feb 18, 2:49 PM
    Failed driving test as sat nav speed incorrect. 7th Feb 18 at 2:49 PM
    Hi, So I failed my 1st driving test yesterday, only because of 1 serious fault (speed).

    Just before a national speed limit it was 30mph zone. When I was about 150 yards from the change of speed I checked my mirrors, as I did so the car went to 31mph as it went slightly downhill at that time.


    The examiner without looking at the speedometer (can only see 70MPH+ from the passenger seat) told me I was speeding. When I looked at the sat nav the speed reading on that was 4 mph faster then the car says (so 35mph instead of 31MPH).

    When we got back to the test centre she said I was speeding failed me, and went without being able ask any questions she went as as they were behind on the tests.

    My driving instructor plugged her sat nav in (the exact same as the examiners use) and hers was 4 MPH slower then the cars speedometer. So between the 2 satnavs there is a 8MPH difference.


    Has anyone else come across this before?

    Is it right that examiners only use sat nav speedometer readings now?

    If so Does that mean I should use the sat nav speed reading from now one?
Page 1
    • AndyMc.....
    • By AndyMc..... 7th Feb 18, 2:54 PM
    • 1,578 Posts
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    AndyMc.....
    • #2
    • 7th Feb 18, 2:54 PM
    • #2
    • 7th Feb 18, 2:54 PM
    So according to your sat nav you were speeding throughout the whole test and not just at one point in time?
    • neilmcl
    • By neilmcl 7th Feb 18, 2:55 PM
    • 11,100 Posts
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    neilmcl
    • #3
    • 7th Feb 18, 2:55 PM
    • #3
    • 7th Feb 18, 2:55 PM
    No you should use the speedo on the car. At the end of the day you were speeding, whether it was 31mph or 35mph. I would still have expected your driving instructor to query this with the test centre though. Was this the examiner's own sat nav they brought into the car?
    • stator
    • By stator 7th Feb 18, 3:20 PM
    • 6,301 Posts
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    stator
    • #4
    • 7th Feb 18, 3:20 PM
    • #4
    • 7th Feb 18, 3:20 PM
    It's possible for a satnav to be wrong. If you weren't stationary when it was first turned on an synchronised then it will be inaccurate. Also if there was a poor signal at the time, due to being in a very built up area.
    Appeal and you might get your test fee refunded.
    You'll still have to take the test again.
    Changing the world, one sarcastic comment at a time.
    • wongataa
    • By wongataa 7th Feb 18, 3:34 PM
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    wongataa
    • #5
    • 7th Feb 18, 3:34 PM
    • #5
    • 7th Feb 18, 3:34 PM
    It's possible for a satnav to be wrong. If you weren't stationary when it was first turned on an synchronised then it will be inaccurate.
    Originally posted by stator
    You won't see a speed on a sta-nav until it has got satellite lock so this is irrelevant.
    Also if there was a poor signal at the time
    Originally posted by stator
    This is correct but if this isn't the case then the sat-nav speed will be accurate.
    • wongataa
    • By wongataa 7th Feb 18, 3:36 PM
    • 1,341 Posts
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    wongataa
    • #6
    • 7th Feb 18, 3:36 PM
    • #6
    • 7th Feb 18, 3:36 PM
    My driving instructor plugged her sat nav in (the exact same as the examiners use) and hers was 4 MPH slower then the cars speedometer. So between the 2 satnavs there is a 8MPH difference.
    Originally posted by samba987
    The only way you can compare sat nav speeds between two devices and a car speed is to have them both on and running at the same time while you are driving as you need to see the numbers from all units for the same vehicle speed, on the same bit of road.
    • nomoneytoday
    • By nomoneytoday 7th Feb 18, 3:37 PM
    • 4,752 Posts
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    nomoneytoday
    • #7
    • 7th Feb 18, 3:37 PM
    • #7
    • 7th Feb 18, 3:37 PM
    Usually a car speedo would over read and the sat nav would be the accurate one.
    Could you see the sat nav speedo?
    • DoaM
    • By DoaM 7th Feb 18, 3:40 PM
    • 4,399 Posts
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    DoaM
    • #8
    • 7th Feb 18, 3:40 PM
    • #8
    • 7th Feb 18, 3:40 PM
    Was this the examiner's own sat nav they brought into the car?
    Originally posted by neilmcl
    That's how I read the OP, but it does surprise me ... why would they need one? (If it's for judging speed then it's not a calibrated device therefore cannot be used for speed measurements - only for guidance).
    Diary of a madman
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    Entries of confusion
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    • Mercdriver
    • By Mercdriver 7th Feb 18, 3:42 PM
    • 1,677 Posts
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    Mercdriver
    • #9
    • 7th Feb 18, 3:42 PM
    • #9
    • 7th Feb 18, 3:42 PM
    Surely this would mean that there is a problem with the car's speedo - i.e. it's under reading the speed, not over reading it, which is not allowed...
    • Mercdriver
    • By Mercdriver 7th Feb 18, 3:43 PM
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    Mercdriver
    That's how I read the OP, but it does surprise me ... why would they need one? (If it's for judging speed then it's not a calibrated device therefore cannot be used for speed measurements - only for guidance).
    Originally posted by DoaM
    New parts of independent driving in the test where the candidate is required to follow directions via a sat nav.
    • AdrianC
    • By AdrianC 7th Feb 18, 3:43 PM
    • 17,602 Posts
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    AdrianC
    That's how I read the OP, but it does surprise me ... why would they need one? (If it's for judging speed then it's not a calibrated device therefore cannot be used for speed measurements - only for guidance).
    Originally posted by DoaM
    Following satnav instructions is a part of the test now - and has been since December.

    Depressing, isn't it?
    • Car 54
    • By Car 54 7th Feb 18, 4:18 PM
    • 3,031 Posts
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    Car 54
    That's how I read the OP, but it does surprise me ... why would they need one? (If it's for judging speed then it's not a calibrated device therefore cannot be used for speed measurements - only for guidance).
    Originally posted by DoaM
    Examiners have been using uncalibrated devices (speedos) to measure speed since 1935. What has changed?

    In practice, all examiners (and most instructors) can judge speed pretty accurately, and would only use the speedo (or satnav) for confirmation before marking a fault.
    • Cash-Strapped.T32
    • By Cash-Strapped.T32 7th Feb 18, 4:19 PM
    • 486 Posts
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    Cash-Strapped.T32
    Was this the examiner's own sat nav they brought into the car?
    Originally posted by neilmcl
    Examiners should all by now be using the exact same make & model of satnav, provided and set up in the car by the examiner (it's a particular Tomtom model iirc).

    So regardless of whatever satnav the pupil has been using, the examiner (and student) should be using the tomtom provided by the examiner.




    ** The reason that examiners all use the same make & model satnav is so that pre-created routes can be produced centrally & pushed-out to examiners with regular updates, to help move away from the old-model way of doing things where there were only 10-15 routes around each town that everyone & his dog learned over time & didn't vary much...

    Creating them centrally & then pushing them out *in theory* should allow the DSA to respond to feedback on routes, and introduce more mixes of A-roads, country roads (where the majority of new drivers end up dying), etc.. rather than the current way we all did it, where you spend 99% of your time on the same residential roads.

    Whether or not any of that ends up happening is of course to be seen - but the rationale for introducing sat-navs in tests does go far beyond simply giving learners practice at reading a screen...
    Last edited by Cash-Strapped.T32; 07-02-2018 at 7:36 PM.
    • lister
    • By lister 7th Feb 18, 7:33 PM
    • 219 Posts
    • 249 Thanks
    lister
    Examiners have been using uncalibrated devices (speedos) to measure speed since 1935. What has changed?

    In practice, all examiners (and most instructors) can judge speed pretty accurately, and would only use the speedo (or satnav) for confirmation before marking a fault.
    Originally posted by Car 54
    Exactly - and DEs are not supposed to use the satnav either, they are only supposed to use the speedo (officially - in practice things may operate differently...).

    And if I remember correctly, you have experience of this business, so would probably back me up when I say that learners who have just failed a test don't always have the best recollection of events...

    If the DE was suspicious of the OPs speed enough to check (either via speedo or satnav), my money says they were doing the 35mph mentioned (or indeed slightly over, as the OP probably slowed slightly before looking).
    • Ocelot
    • By Ocelot 7th Feb 18, 7:54 PM
    • 110 Posts
    • 253 Thanks
    Ocelot
    Following satnav instructions is a part of the test now - and has been since December.

    Depressing, isn't it?
    Originally posted by AdrianC
    What if you don't have a satnav - does the examiner always take one with them?
    • lister
    • By lister 7th Feb 18, 8:04 PM
    • 219 Posts
    • 249 Thanks
    lister
    What if you don't have a satnav - does the examiner always take one with them?
    Originally posted by Ocelot
    The examiner always brings their one - after all they do need to have the route pre-programmed to avoid wasting time... Plus they have all received training on the standard model.
    • Iceweasel
    • By Iceweasel 7th Feb 18, 10:20 PM
    • 4,322 Posts
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    Iceweasel
    If the car the OP used for the teat had been fitted with tyres a size or two bigger (profile or width) than standard then the speedo could easily read less than the sat-nav speed.
    • stator
    • By stator 7th Feb 18, 11:58 PM
    • 6,301 Posts
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    stator
    You won't see a speed on a sta-nav until it has got satellite lock so this is irrelevant.
    Originally posted by wongataa
    Wrong. I used to have a satnav and if you turned it on whilst the car was moving it appeared to work fine, but it was just really inaccurate, like > 10m out and the speed display was often wrong. If you turned it on whilst stationary it was accurate.
    Changing the world, one sarcastic comment at a time.
    • IanMSpencer
    • By IanMSpencer 8th Feb 18, 12:35 AM
    • 1,462 Posts
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    IanMSpencer
    SatNavs tend to under-read when they get signal glitches - some will guess that you are driving at a constant speed in a tunnel for example.

    I would suspect though that while decelerating what actually happened is that the examiner had been watching the Speedo over the course of the test and had seen that the driver failed to decelerate sufficiently before the speed sign. Mainly though, there is a lag between Speedo and sat nav and if you look between them as speed changes you will not get an accurate match.

    When I have compared devices I needed to find clear sky, straight road, constant speed. In those conditions a sat nav will be the most accurate. Anything else and all bets are off for comparison.

    I would expect that although the examiner may have seen the speed on the Sat nav, they also checked the Speedo. OP would not fail for a brief moment of speeding where OP detected and corrected, it is more likely that there was a tendency to slow after a limit sign and did so more than once without the examiner seeing any circumstances like hidden or poorly placed signs.

    Don't believe 8mph difference, I think that the OP spotted a speed on the Sat nav while decelerating then looked at Speedo. Any inexperienced driver is unlikely to hold a constant speed - in fact most highly geared modern cars are not easy to keep to speed unless you properly select an appropriate gear (3rd for 30).
    • Car 54
    • By Car 54 8th Feb 18, 8:48 AM
    • 3,031 Posts
    • 1,903 Thanks
    Car 54

    And if I remember correctly, you have experience of this business, so would probably back me up when I say that learners who have just failed a test don't always have the best recollection of events...
    Originally posted by lister
    Nor even those who have passed!
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