HGV/Coach Speeds

[Butts]

I was under the impression that these vehicles were supposed to be electronically restricted to 55mph.

However when travelling on the Motorway at 70mph I seem to have trouble overtaking them

Am I mistaken in my assumption ?

 

[GlosRail]

Coach is 65 mph, a HGV is 56mph.

Most car speedo's over read by a few mph, so may only be doing about 66mph yourself.

 

[notadriver]

I was under the impression that these vehicles were supposed to be electronically restricted to 55mph.

However when travelling on the Motorway at 70mph I seem to have trouble overtaking them

Am I mistaken in my assumption ?

Lorries restricted to 56 mph. Coaches 62 mph. Car speedos may over-read by 5 mph so you might be doing 65 mph when your speedo is showing 70.

 

[Butts]

Lorries restricted to 56 mph. Coaches 62 mph. Car speedos may over-read by 5 mph so you might be doing 65 mph when your speedo is showing 70.

56mph - I don't think so , has anyone else been overtaken by a speeding lorry?

 

[Ploughman]

If you don't believe that they are limited to 56 then go and take a look at any motorway where you find lorries trying for miles to overtake.
If they were not restricted this would not happen.
The restrictor is linked to the Tachograph and physically stops overspeed.

Tachographs are very accurate and the percentage error is drastically reduced when compared with the average speedo in your car. 1mph compared with 5 mph in a car
If there is one near you try and find one of the roadside speed indicating signs and compare that display with what your speedo says.
There is another way and that is go past a stripey looking car or van parked on the roadside.The driver of that vehicle will let you know what speed you are doing for a small fee.

 

[bb21]

There is another way and that is go past a stripey looking car or van parked on the roadside.The driver of that vehicle will let you know what speed you are doing for a small fee.

... amongst other things.

 

[fowler9]

56mph - I don't think so , has anyone else been overtaken by a speeding lorry?

Never in the UK on a motorway. The police have a field day by ours with car drivers who can't read the speedo though. I'd say most of the time they don't need the speed camera to know someone is speeding. You can tell who is getting pulled.

 

[Zoidberg]

Just popping in to mention that the legal tolerance for a car's speedo is +10mph, not 5mph as seems to have been alluded to a couple of times above. That is, they are allowed to read up to 10% over, but not under.

So, an actual 64mph could be an indicated 70.4mph.

And an actual 70mph could be an indicated 77mph.

 

[Monty]

What about foreign lorries? I swear I was doing 70ish (for legal reasons I will refrain from quoting my exact speed ) and I had a Dutch registered HGV right up my backside on the M3.

 

[fowler9]

What about foreign lorries? I swear I was doing 70ish (for legal reasons I will refrain from quoting my exact speed ) and I had a Dutch registered HGV right up my backside on the M3.

Well if you were perhaps speeding I wouldn't complain about others doing the same, ha ha. Not a great defense in court. At the end of the day I know everyone does it except for me, and my dad (At least he hasn't been caught in some 50 years).

 

[Zoidberg]

Well if you were perhaps speeding I wouldn't complain about others doing the same, ha ha. Not a great defense in court. At the end of the day I know everyone does it except for me, and my dad (At least he hasn't been caught in some 50 years).

This may be of interest to some in this thread.

As I mentioned above, a car's speedo is permitted to over-read by 10%.

The ACPO guidelines (I stress, guidelines) for persecuting for speeding is 10% + 2mph over the speed limit.

Taking the general motorway limit as an example, one may escape persecution if travelling at 78mph. Taking into account the maximum tolerance of a speedo, that would relate to an indicated 85.8mph. But would you bet on your speedo being +10% out?

 

[notadriver]

Easy. A GPS on a level road with good satellite reception at a steady speed will provide a fair indication of how much it's out.

 

[Butts]

What about foreign lorries? I swear I was doing 70ish (for legal reasons I will refrain from quoting my exact speed ) and I had a Dutch registered HGV right up my backside on the M3.

That is a good point , foreign lorries may not be restricted and perhaps these are the ones who seem to be exceeding 56mph by some margin.

 

[fowler9]

This may be of interest to some in this thread.

As I mentioned above, a car's speedo is permitted to over-read by 10%.

The ACPO guidelines (I stress, guidelines) for persecuting for speeding is 10% + 2mph over the speed limit.

Taking the general motorway limit as an example, one may escape persecution if travelling at 78mph. Taking into account the maximum tolerance of a speedo, that would relate to an indicated 85.8mph. But would you bet on your speedo being +10% out?

Its a good point mate but given that a great many motorists I have sat in cars with don't seem to worry unless it is close to 100 on the speedo I guess it is null and void. Purely anecdotal of course but a lot of people will be used to this. If a train crashed breaking the speed limit such as in Spain or America recently there would be an uproar, car drivers know best though.

 

[Butts]

This may be of interest to some in this thread.

As I mentioned above, a car's speedo is permitted to over-read by 10%.

The ACPO guidelines (I stress, guidelines) for persecuting for speeding is 10% + 2mph over the speed limit.

Taking the general motorway limit as an example, one may escape persecution if travelling at 78mph. Taking into account the maximum tolerance of a speedo, that would relate to an indicated 85.8mph. But would you bet on your speedo being +10% out?

In this day and age why are speedos so innaccurate ?

 

[Zoidberg]

Its a good point mate but given that a great many motorists I have sat in cars with don't seem to worry unless it is close to 100 on the speedo I guess it is null and void. Purely anecdotal of course but a lot of people will be used to this. If a train crashed breaking the speed limit such as in Spain or America recently there would be an uproar, car drivers know best though.

Oooh, I wouldn't be travelling with those folk a second time, unless I was driving!

 

[fowler9]

In this day and age why are speedos so innaccurate ?

They aren't, its a good excuse though.

 

[Zoidberg]

In this day and age why are speedos so innaccurate ?

Well, if 100% accurate on new tyres, the speedo will be increasingly inaccurate as the tyres wear and the rolling radius reduces, so there are more revolutions of the wheel for a given distance.

 

[notadriver]

Its a good point mate but given that a great many motorists I have sat in cars with don't seem to worry unless it is close to 100 on the speedo I guess it is null and void. Purely anecdotal of course but a lot of people will be used to this. If a train crashed breaking the speed limit such as in Spain or America recently there would be an uproar, car drivers know best though.

In the UK train drivers are the only group of drivers apart from emergency services permitted to routinely exceed 70 mph.

 

[Butts]

Well, if 100% accurate on new tyres, the speedo will be increasingly inaccurate as the tyres wear and the rolling radius reduces, so there are more revolutions of the wheel for a given distance.

Could you repeat that in English

 

[Zoidberg]

Could you repeat that in English

The speedo works from a gearing or electronic sensor based upon rotations - the sensor is usually on the gearbox output shaft. It displays a speed based upon a certain number of revolutions of that output shaft per mile.

As a tyre wears, it turns a greater number of times per mile and so the output shaft turns more per mile.

Since the speedo reports on turns per mile, as a tyre wears it will show an increasingly higher speed, for any given speed, than when the tyres were new.

 

[Butts]

The speedo works from a gearing or electronic sensor based upon rotations - the sensor is usually on the gearbox output shaft. It displays a speed based upon a certain number of revolutions of that output shaft per mile.

As a tyre wears, it turns a greater number of times per mile and so the output shaft turns more per mile.

Since the speedo reports on turns per mile, as a tyre wears it will show an increasingly higher speed, for any given speed, than when the tyres were new.

Thankyou

 

[Zoidberg]

Thankyou

Welcome - and in speedos in older cars there used to be displayed the turns per mile (TPM) number in small print on the face of the speedo so that if replacement was necessary a unit with the correct gearing could be installed.

EDIT; An example http://www.guess-works.com/Tech/images/TPM_002.jpg

 

[fowler9]

The speedo works from a gearing or electronic sensor based upon rotations - the sensor is usually on the gearbox output shaft. It displays a speed based upon a certain number of revolutions of that output shaft per mile.

As a tyre wears, it turns a greater number of times per mile and so the output shaft turns more per mile.

Since the speedo reports on turns per mile, as a tyre wears it will show an increasingly higher speed, for any given speed, than when the tyres were new.

In an age where my boss can work out where I am phoning in sick from you'd think a car can work out how fast its going. Ha ha.

 

[Zoe]

That is a good point , foreign lorries may not be restricted and perhaps these are the ones who seem to be exceeding 56mph by some margin.

Trucks are limited to 56 mph (90 km/h) and coaches to 62.5 mph (100 km/h) due to an EU directive so the limiters would not just be fitted to British vehihcles.

 

[Zoidberg]

In an age where my boss can work out where I am phoning in sick from you'd think a car can work out how fast its going. Ha ha.

Indeed, but they do not yet have GPS linked speedos - well, not as far as I know.

 

[Butts]

While we are on the subject of permitted speeds, Caravans and Trailers used to display a "50" sticker on the back.

Is that still applicable as I don't seem to see the sign today and they certainly in my experience are often guilty of exceeding 50mph.
--- old post above --- --- new post below ---

Trucks are limited to 56 mph (90 km/h) and coaches to 62.5 mph (100 km/h) due to an EU directive so the limiters would not just be fitted to British vehihcles.

Perhaps in Romania and Bulgaria there are "ways around this" with the appropriate bribe

 

[Zoidberg]

While we are on the subject of permitted speeds, Caravans and Trailers used to display a "50" sticker on the back.

Is that still applicable as I don't seem to see the sign today and they certainly in my experience are often guilty of exceeding 50mph.

The vehicles you mention are limited (unless a lower limit prevails on the road) to 50mph on single carriageway roads and 60mph on dual carriageway and motorways.

See https://www.gov.uk/speed-limits

Type of vehicle Built-up areas mph (kph) - Single carriageways mph (kph) - Dual carriageways mph (kph) - Motorways mph (kph)
...
Cars towing caravans or trailers (including car-derived vans and motorcycles) 30 (48) - 50 (80) - 60 (96) - 60 (96)

 

[fowler9]

I suppose we should be grateful we have pretty safe roads and just go with it. Anyone who doesn't like it should slow down, start using their indicators and not park in bus stops or on double yellows. Alas many people think enforcing this is a war on the motorist which it isn't.

 

[90019]

If you don't believe that they are limited to 56 then go and take a look at any motorway where you find lorries trying for miles to overtake.
If they were not restricted this would not happen.
The restrictor is linked to the Tachograph and physically stops overspeed.

Though there are ways to disable the limiter, but getting caught will get you in a fair bit of bother.
I know of one way on certain lorries (though I don't know if it works with digital tachos) that is almost impossible to detect without taking the whole thing to pieces if installed correctly, but for obvious reasons I'm not going into details on a public forum.

Alternatively, I know of quite a few lorries running about with the tachos calibrated wrong.

Tachographs are very accurate and the percentage error is drastically reduced when compared with the average speedo in your car.

Tachos also have to be inspected every two years and calibrated at least every six.

56mph - I don't think so , has anyone else been overtaken by a speeding lorry?

Yep.

The most memorable was being passed by a Scania R730 Topline pulling at least 75mph hauling a fully laden flatbed. It was quite a sight.

I've had a 94D up to 64mph a couple of years back.
--- old post above --- --- new post below ---

This may be of interest to some in this thread.

As I mentioned above, a car's speedo is permitted to over-read by 10%.

The ACPO guidelines (I stress, guidelines) for persecuting for speeding is 10% + 2mph over the speed limit.

Taking the general motorway limit as an example, one may escape persecution if travelling at 78mph. Taking into account the maximum tolerance of a speedo, that would relate to an indicated 85.8mph. But would you bet on your speedo being +10% out?

I'm going to cross post a quote from another forum, from a copper, about this very subject only a matter of days ago:

These aren't hard and fast rules and the Safety Scamera Partnerships don't have to rigidly stick by them.

The 10% +2mph thing is a discretionary limit set by ACPO (Association of Chief Police Officers) and is supposed to be nationwide. These figures relate in no way to the acceptable tolerances with over-read and underread for speedos. (I can find out for you next week from our CI's if you want.)

However, all it takes is one snotty Chief Constable of a force to say "No. Zero tolerance to speeding" and the limit will be set hard and fast at, say 30 in a 30 zone.

It's not 10% +2 is what you can get away with, the 10% +2 is where the fining/points start

For example -

30mph zone.

You're doing 34. That's OK. You'll likely get away with that. That's 10% +1.

If you're doing 35, which is 10% +2, that'll land you with an NIP.

It is not, as most people think 36 (10% + 3) at which the enforcement starts.