/ Motoring

Which driver habits annoy you: bad indication, tailgating…

'Got patience?' painted on the back of a lorry

Narrowly missing a collision when a driver fails to indicate properly isn’t much fun, as I found out. This, along with drivers hogging the middle lane, has to be my biggest pet hate about others drivers – what’s yours?

Earlier this week, I was cycling to the station – in a hurry not to miss my train – and I came up behind a car which was, well, all I can say is ‘hovering’ beside a vacant parking space. The car was indicating left as though he was about to go in.

The road was clear, with no oncoming vehicles, so I decided it was safe to go past on his right-hand side. As I pulled up alongside, he changed indicators and pulled forward and right, across the road, into my path.

His action caused me to have to swerve, and both of us to brake sharply, in order to avoid me putting a large dent in his door (never mind how much damage could have been done to me or my bike!).

The driver apologised with a wave of his hand and a sheepish smile, and I restrained myself from saying what I thought, either in voice or with hand signals. After all, my focus was on catching that train, rather than showing my feelings or holding grudges.

Keep calm and carry on

My advanced driver training taught me two particular things for such circumstances. The first is to try to anticipate when the actions of other road users might be hazardous to my safe progress. As I didn’t hit him, I think that one was just about achieved. The second was to remain calm, even when something unexpected does happen, which I also managed quite well.

This sort of incident is, after all, par for the course for most commuting cyclists, and it’s probably only as bad (and potentially dangerous) as the habits some cyclists exhibit all too often. You know the ones – driving through red traffic lights or squeezing along the inside of a bendy bus that’s waiting to turn left.

The reality for me was that, luckily, I avoided the accident, caught my train and completed my journey without further incident.

What are your pet hates?

The very next day, a colleague asked me about which of the driving habits of others most wind me up. As I say, I try not to be ‘wound up’ when I’m on the roads, but I had to mention the incident with the indicating car, as well as the impetuous behaviour of too many cyclists.

And it’s not surprising to see that failing to indicate came top of a recent survey by confused.com about people’s biggest irritants on the roads. Other pet hates included tailgating and refusing to let others out at junctions.

I added to the list a gripe I’m sure I share with many. I really think UK drivers need more formal tuition about motorway lane discipline. Our motorways would flow so much more smoothly and efficiently if people used the lanes properly.

But the number of drivers who think the middle lane is their personal territory really annoys me and, in my view causes unnecessary and hazardous disruption to drivers trying to follow the highway code.

Are you with me – or the survey – with these pet hates or do you have others to add to the list?

What's your biggest pet hate about other drivers?

Tailgating (22%, 224 Votes)

Drivers on mobiles (20%, 199 Votes)

Hogging motorway lanes (19%, 192 Votes)

Bad indication (14%, 141 Votes)

Driving too slowly (8%, 84 Votes)

Dropping litter out of car windows (6%, 57 Votes)

Speeding (4%, 40 Votes)

Other – tell us in the comments (3%, 32 Votes)

Undertaking (2%, 23 Votes)

Not letting other drivers out at junctions (1%, 14 Votes)

Total Voters: 1,006

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A worker says:
5 November 2011

People who park their car anywhere they feel and in anyway they like with total disregard to the consequences of their action.

Belinda Z'Abat says:
23 November 2011

Couldn’t agree more. I have to find a place to park every Friday night where there are very limited places.
It would appear, from years of seeing this, that small cars take up the most room !
A tiny Corsa regularly takes up a position that means instead of 3 cars being able to park, only it can do so.
But then, after reading some of the previous posts, it’s obvious I should shut up and “be tolerant”.

Particularly those who block others’ drives or park on the pavement. Or the learner driver who, the other day, parked in the middle of the road while the instructor had a long chat with him/her, being totally unaware of the traffic biuilding up behind, until someone decided to hoot (I blame the instructor, not the learner).

Drivers who pull out right in front of you, especially if they they then accelerate slowly and drive well under the speed limit in front of you.

Second on the list is drivers who leave well more than the 2 second gap when moving off on a green light when in traffic and then go through red, leaving traffic that could easily have made it through the lights normally stranded to wait for another cycle of the lights.

Graham says:
23 January 2012

Even more annoying are drivers who pull out in front of you then turn off at the next junction. Invariably they have to wait for a gap if they are turning right.

ric the trucker says:
7 November 2011

The most annoying and dangerous driver is the one who doesn’t know how to join a motorway safely. It’s a give way guys! Read your highway code!

Graham says:
23 January 2012

It may be Give Way but it’s also join the motorway at the right speed and filter into the flow of traffic.
I don’t have a problem with other drivers joining the motorway without giving way if they are traveling fast enough but I do object to either following a driver down the slip road doing 30-40 mph or those who join at the wrong slow speed. You should be traveling at the same speed as the traffic already on the motorway, so that you can filter in safely. The speed limit is 70mph!
You are also supposed to move out of the inside lane when you are approaching a slip road joining the motorway, to allow other drivers to join safely. Drivers who sit adamantly in the inside lane are just as dangerous.

Harry says:
8 November 2011

First: Speeding-not just the over the limits stuff but going so quickly so that in many situations the margins for error are dangerously reduced, e.g. cars speeding around roundabouts leaving those wanting to join it having to play ‘chicken’ to get into the flow; ditto going round corners which might conceal pedestrians, a hold up etc.

Second: tail gating, especially when I’m keeping to the 30mph limit. It’s simply bullying and severely reduces the safety margins. I’d love to react by reducing my speed to allow for the tight braking distance but I fear that I’d get the full lights on/horn blowing/arm waving display of masculinity.

Mrs AI Bullock says:
19 January 2012

Not mentioned as a major irritant is “Dazzle.” Offending drivers forget they have left an unlit road and do not go to dipped lights. But also, main offenders’dipped lights are set for too long a “throw.” 4×4 s are significant offenders.If one flashes them to indicate they have not dipped, their reply is “oh yes I have” accompanied by a hugely powerful blast from their main beams. MOT tests might curb some offenders who have set their dipped lights too high, but for how long.

I think this is more than an irritating driving habit, but I do not see an easy solution to deal with dazzle. It was not too bad when all vehicles were fitted with a pair of standard power headlights but now many vehicles have duplicated main beams, and brighter bulbs (gas discharge or simply higher power) have become common. Sometimes headlights that have been upgraded to take brighter bulbs produce a lot more dazzle on the dip setting than original equipment.

I think we should go back to vehicles having a pair of 60/55 W headlights. Anyone who claims that they need brighter lights should not be driving on public roads.

It’s fairly easy to spot whether headlights are on main beam or dipped lights set incorrectly. If you are not blinded completely, look carefully before flashing your lights at the oncoming car.

Mrs AI Bullock says:
19 January 2012

There has been much discussion about scrap metal in the media. Now consider an individual householder who requires a new CH system and a hot water cylinder. Is it sufficient to accept a contract in which the provider states all scrap will be removed. Should not the provider state the scrap value of the main metal components which are to be removed and reduce the contracted price accordingly.

John Ingram says:
23 January 2012

Mrs Bullock should have gone to specsavers, this comment thread is regarding pet hates while driving, not scrap plumbing bits and contracts.

Maureen Graham says:
19 January 2012

I am annoyed by thoughtless drivers who insist on sitting at traffic lights with their foot on the brake instead of engaging neutral. It can be blinding with the brightness of the lights, not to mention being inconsiderate. I am tempted to follow them with my headlights on full but restrain myself – sometimes with difficulty!!

I find the LED brake lights on vehicles a particular problem, since these are sometimes much brighter than the traditional 21 watt incandescent bulbs.

It is courtesy not to dazzle other drivers, and I switch off the headlights too if stuck in a traffic jam for any length of time.

Thoughtless motorway drivers are even worse. Every day I end up queuing on the M4 going to and from work. During dark mornings and evenings 90% drivers seem incapable of using their handbrakes or simply taking their foot of the brake and you end up being blinded by the person in front of you. I fail to understand why nobody seems to give a thought to the person behind them. The introduction of brighter LED lights (especially on Audis) and the third eye level brake light just makes the experience even worse. Under these circumstances I’ve taken to wearing sun glasses to reduce the unbearable glare.

Veronika Pond says:
19 January 2012

My pet hate is being blinded by the motorist in front when in a line of stationary traffic, simply because they are unsure how to use the handbrake.

Do they still teach learners to use the handbrake and take the foot off the footbrake when stationary? People don’t seem to be doing that any more. I don’t even see police cars’ brake lights go off when stationary these days.

I agree totally about motorway lane discipline, if the uneducated people who sit in the right hand lanes for no reason did not do this, there would be almost no undertaking and a lot less tailgating. I wouldn’t mind betting that it is EXACTLY the people who hog the outside lanes who also complain about these two things! There would be a lot better traffic flow and reduced trip times too. Where do people get this idea that they should sit in the outside lanes?

roger parker says:
25 January 2012

I always sit in the middle lane doing 70 mph if you and a load of other bad drivers all want to get past me, you will need to break the speed limit and break the law!! should you realy be doing this ?.

John H says:
20 January 2012

My latest pet hate. Lady driver sitting at traffic lights on Main Street with white bib under chin cleaning her teeth with electric toothbrush, is this a first?

DaveR says:
20 January 2012

One that I don’t think has been mentioned. At night when the pupils of the eyes are opened, sitting at traffic lights, behind a driver with his/her foot on the brake is extremely iritating. Modern brake lights are very bright and can dazzle the driver behind. I think the highway code suggests putting the car in nuetral and putting the hand brake on.

Terry says:
21 January 2012

I really have a problem with people who drive with their driving lights on. Apart from the fact they are clearly medallion substitutes (no wonder people call them pratlights), it is illegal except in adverse conditions. They also contribute significantly to the glare when they come up behind you at night, creating a distraction to which I react by slowing down.

John L says:
3 February 2012

Do you mean FOG lights, which can only be used legally in Fog ( visibillity of less than 50 yds) or flling snow.

Mrs AI Bullock says:
22 January 2012

I have noticed how inadequate reflectors on the rear of cars parked at night are.Some might as well not be there.
This is in marked contrast to the effective reflecting material used on road signs.
Whether cars are parked on the road or halfway across a pavement there is a real danger of rear ending parked cars at night. Were reflectors down- graded in importance because bright reflectors might be confused with brake lights ? So what !

John Ingram says:
23 January 2012

Mrs Bullock definitely should have gone to Specsavers, or needs to drive slower at night if she can’t see a ca whichr is parked in front of her, because the reflectors are not shining.
By the way road signs are a totally different material to rear lights and reflectors on cars.

John Ingram says:
22 January 2012

My pet hate is people using fog lights illigally when visibilty is. The Highway Code states as follows;

RULE 226

You MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet). You may also use front or rear fog lights but you MUST switch them off when visibility improves (see Rule 236).

RULE 236

You MUST NOT use front or rear fog lights unless visibility is seriously reduced (see Rule 226) as they dazzle other road users and can obscure your brake lights. You MUST switch them off when visibility improves.

Absolutely, though if use of rear fog lights does obscure brake lights it is because of poor car design in which the brake fog light(s) are close to the brake lights. I don’t know why rear brake lights are not combined with tail lights. I have only seen a couple of models where this has been done.

@John Ingram: I agree, but don’t get too annoyed by others who leave their fog lights on: it may not be deliberate. I once noticed that I had just driven a long distance with my fog lights on. I hadn’t turned them on myself, but my passenger had. The fog light switches in my car are in the middle, next to the handbrake, between the two front seats, and the fog light warning light on the dashboard does not look very different from the normal sidelights warning light, so is easy to miss.

@wavechange: I thought it was quite common to have brake lights combined with tail lights, and that this was the case in most cars. Certainly most (if not all) of the cars I have ever owned. Have you not seen all those light bulbs in car spares shops and petrol stations with two elements inside, and three contacts at the end (one common, one for brake, one for tail)? Hold on, maybe not at petrol stations, they don’t seem to sell car parts anymore, but sell groceries, coffee and pastries instead, after all car parts are only bought by motorists and you wouldn’t find any of those at a petrol station, would you?

(Sorry for the rant but I once broke down and asked a petrol station manager if they stocked tow ropes. He didn’t know what a tow rope was!)

Sorry, I mean fog lights combined with tail lights. Brain not engaged.

The bulbs you mention could be used for this job.

John Ingram says:
23 January 2012

Re Fog lights, in my earlier post (Posted 22 January 2012 at 8:32 pm)I was really referring to front fog or driving lights, combined with head lights which are regularly, illegally used when visibility is good, rear fog lights are not so often a problem to me. I repeat the Highway Code rules below, which ARE law.
I think a campaign on Facebook and other social websites may raise the profile of a few of these valid driving gripes and prompt people to drive more aware of the law.
1. RULE 226
You MUST use headlights when visibility is seriously reduced, generally when you cannot see for more than 100 metres (328 feet). You may also use front or rear fog lights but you MUST switch them off when visibility improves (see Rule 236).
RULE 236
You MUST NOT use front or rear fog lights unless visibility is seriously reduced (see Rule 226) as they dazzle other road users and can obscure your brake lights. You MUST switch them off when visibility improves.
By the way, I didnt write the above, I cut and pasted from the official Directgov website; http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/DG_069859

I must agree with a previous post regarding thoughtless or lazy people holding the car stationary with the foot brake rather than use the hand brake.

Oh, and while here what about people who sit in the middle lanes of motorways, even when the inside lane is empty, why is it so different to a dual carriageway, where you normally return to the nearside lane, as soon as possible.

Graham says:
23 January 2012

Having read the article, I’m surprised that drivers have a problem with drivers who don’t let other drivers out of side roads.

I rarely let anyone out because you are asking for someone to run into your rear end if you stop to let someone out and invariably there is always a gap they can pull into if they just have a little patience.

I find it extremely annoying when the driver in front stops to let someone else out because it is obvious they never check their mirror to see who is behind them.

I always check to see if there is a suitable gap somewhere in the traffic behind me into which they can turn out and if there is, I don’t let them out, as far as I’m concerned they can wait for the gap!
If the traffic is slow moving or stopped, then it’s different, I always let people out.

And whilst we are on the subject, I also find drivers who are turning right and pull out across the traffic, when there is not a suitable gap in the lane they are joining, and therefore have to stop and block traffic, extremely annoying. They hold up traffic and cause accidents. They should wait for a suitable gap in both directions before pulling out at all.

“… I rarely let anyone out because you are asking for someone to run into your rear end if you stop to let someone out and invariably there is always a gap they can pull into if they just have a little patience.

And whilst we are on the subject, I also find drivers who are turning right and pull out across the traffic, when there is not a suitable gap in the lane they are joining, and therefore have to stop and block traffic, extremely annoying. They hold up traffic and cause accidents. They should wait for a suitable gap in both directions before pulling out at all. Graham”.

In busy roads, there may not be a gap that develops. Just slowing down a little to leave a gap for someone to pull out (without needing to come to a complete stop) is both courteous and safe. As to the pulling out across traffic to turn right, again it may be the only option on a busy road. And again, it takes consideration and anticipation from the driver across whose path one has had to go. In busy conditions, following your comments, is it any more considerate to hold up the traffic behind you for ages, as they also want to emerge? This is equally dangerous, as people behind lose their patience and try to squeeze into a narrow gap, perhaps even mounting the kerb, or start hooting and flashing.

It takes common sense and consideration from all cioncerned.


Couldn’t agree more – It is the maximum speed – not as some posters seem to think a minimum. No wonder there are so many crashes.

Agree also there are some places where It takes common sense and consideration from all concerned.

“Having read the article, I’m surprised that drivers have a problem with drivers who don’t let other drivers out of side roads.”
I suspect that you read the wrong article Graham – the grumble was about letting cars join Motorways at slip roads. A vastly different situation from the problem with drivers waiting to join the main road from a side road. Really you can’t let them join because there is no valid way of signalling your intention to them is there?

John Ingram rightly talks about Fog Lights incorrectly used, but what annoys me is the number of vehicles using Headlights, dipped or otherwise, in broad daylight. This causes dazzle if they are approaching you on a rise or close behind, which is expressly forbidden in Rule 114. It appears to be an increasing habit by some drivers, headed by ‘white van man’, whose vehicles are highly visible anyway! Mind you, many of the so called ‘running lights’ are excessively bright, even being dipped headlights in a number of manufacturers. i’m surprise that the Gvt. didn’t specify the form that such lights should take, eg wattage & position etc.

Does this point extend to mortorbikes? By law, they always have to have their lights on.

Motorbikes – DOH! Finger trouble.

roger parker says:
25 January 2012

What I don’t understand ,is why bad drivers accuse me of not moving over on the middle lane of a motor way. I drive at the legal limit of 70 mph and stay in the middle lane .I do not move to the inside lane because to do this I am then continualy going from one lane to the other ,more lane changes lead to more accidents . Any driver wanting to pass me or take my place in the centre lane has to exceed the speed limit and break the law.Driving as I have discribed I notice cars continually flying past me in the fast all breaking the law.So I will continue to stay in the middle lane doing 70 mph , have been driving fifty two years without an accident or speeding fine .

The problem is that speedometers have a 10% permitted tolerance so if you are travelling at an indicated speed of 70 it is possible that you are actually only doing 63. The car overtaking might also have an indicated speed of 70 but is actually doing over 70. Personally, I keep to the left hand lane unless it is occupied by a series of slow moving vehicles.

That tolerance is 0% to PLUS 10% which means your speed will always be the same as or less than what is indicated – never more. I agree with Tony P – keep to the LH lane. Not only that – I happily undertake when the LH lane is empty and the rest of the world is stuffing the middle and RH lanes. Just don’t undertake near junctions as drivers often move to the LH lane without warning. But then again they do have mirrors don’t they?

I have driven a lot in the USA where passing on either side is permitted. This allows more relaxed driving because there is less need to change lanes, just stick to the one that is moving at the desired speed. There are a few other lessons we could learn from the USA, especially the ability to turn right when the traffic lights are red (it would be turn left in the UK). Before anyone comments that this would be dangerous perhaps I should add that the turning traffic has to treat the junction as if there was a stop sign and give way appropriately.

proboy says:
25 January 2012

YOU are one of the many problems, with our motorway system, like lots of others you need to understand why there are 3 lanes and use them, like a previous correspondent correctly suggested, just the same as a duel carriageway.

With respect you probably have not been taught HOW to CORRECTLY drive motorways, read the Highway Code IT IS VERY, VERY CLEAR, you are wrong.

Unless the nearside lane is extremely busy and slow, return @ 70mph while all the other lanes pass you (illegally I know) in good conditions (weather and traffic permitting) the Police will generally turn a blind eye to drivers up to about 80mph, but you are correct and happy at 70mph.

Moving back to the nearside also keeps you more alert and aware, move lanes rather than to monotonously sit in the middle and get drowsy and annoy others.

But don’t forget to check you mirrors and signal before you move lane, don’t get lazy like all those who forget to signal, not just on motoorways.

Roger, you tell us you have been driving for 52 years without accident, congratulations on that. However, reading your comments about motorway driving & your stubbornness & self-righteousness to “hog” the centre lane, (yes, albeit at the legal, 70mph limit), suggests you need re-educating & understanding of the “real world” on the M-ways.
I too have held my car license for a long while, 58 years, but I’ve tried to keep up with the modern world of motoring.
I suggest you enrol with the IAM, (Institute of Advanced Motorists), & see how you get on. It’s a very relaxed & educational process & whilst I underwent my observation drives I was indeed encouraged, no, expected to speed up to 80mph in order to safely pass other vehicles driving below the 70 limit. ALWAYS PULLING BACK INTO THE CLEAREST LEFT HAND LANE AFTERWARDS!
Sorry, Roger, but you are one of my pet motoring hates & I feel from your comments that you are not confident enough to change lanes on fast moving motorways these days.
I agree with “clint kirk’s” response too.

proboy: “signal before you move lane, don’t get lazy like all those who forget to signal”

I agree with what you said above, but I admit that I don’t always signal. I use my mirrors, ensure I am fully aware of where I am, where I am going, and where everyone else is and where they are going. Then I only signal to change lane if I deem such a signal to be of any interest to anyone.

For example, if I have just passed a slower vehicle, and there is no other vehicle in front and all vehicles behind are slower, then I don’t see any point in indicating to get into the inside lane.

Would anyone care to correct me with a convincing argument as to why I should signal in the above described situation.

Proboy: Thanks for the entertaining typo. I think one of the major problems is that some people do use the roads as duel carriageways! I presume you intended to type ‘dual carriageway’.

Tony P,

Whilst passing on either side is permissible in the USA, is it not dangerous to overtake on the inside lane? The driver in the next lane may want to change lanes and not see you in the blind spot.


You have to realise that all drivers are well aware of the situation and check mirrors on both sides before changing lanes. Added to this, there is much more tolerance to lane changing. I usually found that if I gave enough warning of an intent to change lanes then a gap would appear. In the UK, indicating an intent to change lane often results in drivers closing up to keep you out!

Louis: “indicating an intent to change lane often results in drivers closing up to keep you out!”

That’s one of my pet hates. What are they trying to achieve with such behaviour?

Keith says:
12 February 2012

Roger it is not your job to ” police ” the traffic. By sitting in the middle lane you cause considerable frustation to other drivers. So you move to the inside lane and observe the highway code !!!!!

roger parker says:
25 January 2012

I think the 10% tolerance you refer to was intended for the older car and whilst it still applies to a modern car I believe if my speedo shows 70mph ,thats the speed I am doing. Going back to the point I was making ,if you must overtake me you would be breaking the law.This must not be encouraged.

Roger: “if you must overtake me you would be breaking the law.”

Not necessarily. I could be a member of the emergency services.

More to the point, it is not up to you to police the motorway and dictate who is allowed to exceed the limit. What happens in practice, is that you get a long column of drivers in a hurry overtaking you in the right-hand lane because you single-handedly decide that the three-lane motorway should be turned into a two-lane motorway.

Then you get a police car answering an emergency call, approaching the column of cars in lane 3 with blue lights flashing. The driver of the car just in front of the approaching police car sees the blue lights in his mirror, sh*ts himself, thinking he’s going to get pulled over for speeding, and sharply applies his breaks. Because of that, he’s just suddenly dropped from 79mph to 63mph. If this doesn’t cause an accident behind him, it will cause a tailback.

And by the way, just because your car is new, and even if the speedo is digital, doesn’t mean it’s accurate. There are still many new cars with inaccurate speedos.

And, lastly, the middle lane on the motorway is statistically the most dangerous one to be in. You may not be changing lanes yourself, but drivers on both sides of you will be.

You only have to change your old worn tyres to new tyres, or perhaps winter tyres, and your speedo will then be giving a different indication for the same actual linear speed. If you check using a Satnav then make sure you are travelling on a true level surface. Going uphill or downhill your linear speed will be greater than the Satnav says. (Yes, I was a Surveyor in a previous existence).

Traveller, interesting stuff! I always assumed that my GPS was accurate. I was aware of the tolerance, as I had read about it elsewhere and when I’m doing 32 on the speedometer, the roadside light up speed signs say 30.

John Ingram says:
29 January 2012

Traveller, this link is not actually within the scope of this forum but I feel I must add a comment, as it was me who first mentioned GPS as an accurate method of checking your actual speed on this forum, you may be a surveyor but NOT a rocket scientist and one must get the facts correct before writing confusing comments.

I agree there will be small differentials on the accuracy of GPS systems, but considering the satellites orbit the earth @ 11,000 nautical miles above the Earth, and GPS works by measuring the distance between satellite and GPS receiver, measured in the time the signal takes to reach the GPS unit and at least 4 satellite signals are required, the very high accuracy of the GPS clocks (to about 14 nanoseconds) and continuous transmissions from the satellites, travelling the types of gradients of hills encountered on most UK and European motorways, a rise or fall of a few metres over say a kilometer will make such a small difference to your speed as to be unreadable against any normal speedometer readings, this is so logical I am surprised by the comment.

So under pretty normal conditions GPS speed readings are still far more accurate than most if not all standard in car speedos. Another fact.

John Ingram, I agree that satnav is far more accurate than conventional dashboard speedometers. But I have also heard from people who thought that the satnav speed readout was completely accurate. I would estimate that it may be +/- 1mph at typical motorway speeds. While that’s far more accurate than dashboard speedos, it’s still not completely accurate because your absolute position at any moment is given to an accuracy of a few metres (unless you are the US military, who are given much more accuracy). So when the devices averages your position over a certain amount of time, it only has your distance travelled with +/- a few metres accuracy.

Also, I imagine that satnav devices take position samples at fixed regular intervals. I don’t know what the intervals are, but if you are driving round a bend at the time (instead of going in a straight line) the device will calculate the distance as a straight line between the two sampled points, which will be shorter than the arc that you have actually travelled. But I think the sample intervals are short enough to make this effect minuscule, unless you are going very fast in a very very tight circle (with the car tethered to a pole in the centre of the circle to prevent it losing grip and going off at a tangent.)

John L says:
3 February 2012

I now have a supplementary speedometer that works using GPS, it also has several other functions, that is accurate to + or – 0.1mph. It never agrees with my car speedometer, always shows a slower speed, my car is not that old being Y reg so the speedometer would be working to modern tolerences.

Sorry, but the GPS measures your distance against time on the geosphere. It really doesn’t matter how far away the satellites’ orbits are. Think on …… If the gradient is 1 in 10 up or down then your linear speed will not be the same as your road speed – which is what a radar speed measuring device will quote. You will find that magistrates believe the radar device rather than your SatNav! with good reason.

@John L – when you quote +/- 0.1 mph are you really talking about accuracy, or just precision?

@traveller – I seem to remember reading that GPS is capable of giving your position in three dimensions, so, theoretically, GPS devices can give you your true speed, and not just the horizontal component of your speed. Whether the GPS devices actually do that, of course, is a different matter.

I’m not sure exactly what you mean by “linear speed” and “road speed” but I assume by the latter you mean the speed at which the car is travelling and “linear speed” to be its horizontal component. At a 1-in-ten gradient, the horizontal component would be

horizontal speed = speed * sqrt(10^2 – 1^2) / 10 = 0.995 * speed

(by Pythagoras)

In other words, if your GPS device indicates a horizontal speed of 70.0 mph, your true speed would actually be 70.36 mph. I don’t think you would get prosecuted for doing 70.36 mph.

For example, if I have just passed a slower vehicle, and there is no
other vehicle in front and all vehicles behind are slower, then I don’t
see any point in indicating to get into the inside lane. Would anyone care
to correct me with a convincing argument as to why I should signal in the
above described situation.
( c k)

As a matter of courtesy AND good practice, besides you may not have
known or could have prognosticated what the driver(s) of the vehicle(s)
you’ve passed may or may not have wanted to do at any given moment
in time and you shall be estopped from denying you have done the
right and proper thing if anything untoward shd have happened.

In spirit of if not actual Highway Code.

Totally agree.

Furthermore, if you get into the bad habit of signalling only when you think you should, there is always the risk of missing a situation when you should have signalled and you did not. Better for things to be the other way round.

Drivers who fail to signal their intentions are one of my pet hates and they make me very angry. At best, they cause inconvenience and at worst, they are dangerous.