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Old 24th Apr 2017, 21:29   #1 (permalink)
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speed limits in practice

In order to avoid hijacking the other thread about speeding offences I started here.

Here's one for you: Last time I went up the M42 dual carriageway secton between the M6 and Castle Donnington it was nose to tail in both lanes with the right hand just creaping past the left hand lane. It was like this almost up to the M1 junction but we did find out what was going on.

Anyone like to have a guess?

no?

keep scrolling down.

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It was all caused by the Army running a sensibly spaced convoy of about 25 trucks and Landrovers all driving at 55mph and the HGVs all overtaking at 56mph. Due to the spacing of the Army vehicles the HGVs were not using the left hand lane at all and thus preventing any cars from getting by them.

Of course, if the Army had been going at 57mph the situation would have been the same but 2mph faster!
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Old 24th Apr 2017, 21:46   #2 (permalink)
 
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Since it is an offence to break into an Army or any other official convoy, once committed to overtaking, the trucks have to continue to pass the entire convoy in the right hand lane.

The trucks obviously have 5mph leeway to overtake the convoy before hitting the 60mph limiter, so not unreasonable for them to want to pass given the time constraints the drivers are under to make their deliveries.

Probably worth considering that the speed limits are maximum speeds and not targets to be attained at all times. Inconvenient when you are used to barrelling down the offside lane at a steady 85mph, nose to tail with other executive motors.
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Old 24th Apr 2017, 21:58   #3 (permalink)
 
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Originally Posted by G0ULI View Post
The trucks obviously have 5mph leeway to overtake the convoy before hitting the 60mph limiter, so not unreasonable for them to want to pass given the time constraints the drivers are under to make their deliveries.
Not so obviously. HGVs are limited to 56mph (90kph)
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Old 24th Apr 2017, 23:03   #4 (permalink)
 
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Not so obviously. HGVs are limited to 56mph (90kph)
Coaches will hit 60mph.
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Old 25th Apr 2017, 00:53   #5 (permalink)
 
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The speed limit for lorries is 60mph on dual carriageways in the UK, but you are correct in pointing out that European speed limiter settings stipulate they must be set at 56mph. So anything that travels abroad could well be creeping past at 1mph faster than the convoy. Picky, picky, picky!
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Old 25th Apr 2017, 01:16   #6 (permalink)
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Wonder why the police didn't ask the Army convoy to increase speed to 60mph for a while, until congestion cleared? Can't believe the Army have any road vehicles these days that can't comfortably do 60mph?
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Old 25th Apr 2017, 01:23   #7 (permalink)
 
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This will be a problem with self-driving cars which it is rumoured will be travelling in convoys during early experiments on the roads. Can you overtake a convoy, and then if necessary cut back in/through in order to exit a motorway/expressway/dual carriagway, for example?
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Old 25th Apr 2017, 02:18   #8 (permalink)
 
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Speed limiters, that's crazy talk! I was passed by a Peterbilt, here in the US, I was doing 70 when he knew by me. Posted limit was 65.

GF
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Old 25th Apr 2017, 06:20   #9 (permalink)
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So anything that travels abroad could well be creeping past at 1mph faster than the convoy. Picky, picky, picky!
It only takes one.
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Old 25th Apr 2017, 08:23   #10 (permalink)
 
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Originally Posted by jolihokistix View Post
This will be a problem with self-driving cars which it is rumoured will be travelling in convoys during early experiments on the roads. Can you overtake a convoy, and then if necessary cut back in/through in order to exit a motorway/expressway/dual carriagway, for example?
I would say that cutting through a convoy to get to an exit is borderline dangerous driving. There are already enough idiots who try to leave the motorway at the last possible minute because they have no patience and don't think ahead.
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Old 25th Apr 2017, 08:36   #11 (permalink)
 
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The reason I ask is that the fatal Florida Tesla crash where the driver was rumoured to be watching a DVD, was caused by a long wheelbase truck trying to exit from the middle lane. He pulled into the gap in front of the Tesla, probably finding the largest gap available, but the Tesla did not 'see' the flatbed moving into its lane, and did not fall back a little as a natural human driver would have.
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Old 25th Apr 2017, 08:39   #12 (permalink)
 
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Originally Posted by andytug View Post
I would say that cutting through a convoy to get to an exit is borderline dangerous driving. There are already enough idiots who try to leave the motorway at the last possible minute because they have no patience and don't think ahead.
Depends on the length of the convoy. In the case quoted by the OP here if it is 25 vehicles long, especially if the road isn't straight, you might have gone past the tail of the convoy well before it became apparent that you wouldn't get past the front vehicle in time to make your junction.

I must admit that I didn't know cutting through an army convoy was illegal, although obviously carving through too small a gap between 2 vehicles in any circumstance would constitute dangerous driving.
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Old 25th Apr 2017, 08:41   #13 (permalink)
 
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Since it is an offence to break into an Army or any other official convoy,
Please quote the legislation regarding this comment.
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Old 25th Apr 2017, 08:43   #14 (permalink)
 
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Quote:
Originally Posted by jolihokistix View Post
This will be a problem with self-driving cars which it is rumoured will be travelling in convoys during early experiments on the roads. Can you overtake a convoy, and then if necessary cut back in/through in order to exit a motorway/expressway/dual carriagway, for example?
Oh dear! If these SDC's are prone to road rage then we can look out!
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Old 25th Apr 2017, 08:50   #15 (permalink)
 
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Originally Posted by jolihokistix View Post
The reason I ask is that the fatal Florida Tesla crash where the driver was rumoured to be watching a DVD, was caused by a long wheelbase truck trying to exit from the middle lane. He pulled into the gap in front of the Tesla, probably finding the largest gap available, but the Tesla did not 'see' the flatbed moving into its lane, and did not fall back a little as a natural human driver would have.
Not true - the truck was turning across the Tesla's path from the opposite carriageway and direction.
http://www.theverge.com/2017/2/1/144...-patrol-report
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Old 25th Apr 2017, 09:05   #16 (permalink)
 
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andytug, thank you for this article. It's the best one I have read and explains it quite clearly. Now I wonder how reports at the time managed to get it so wrong.
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Old 25th Apr 2017, 09:09   #17 (permalink)
 
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andytug, thank you for this article. It's the best one I have read and explains it quite clearly. Now I wonder how reports at the time managed to get it so wrong.
Possibly some in the media with vested interests in Tesla's tech failing? Who knows.
Think the biggest fail was probably calling the cruise control "Autopilot" when it's nothing like one.
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Old 25th Apr 2017, 10:55   #18 (permalink)
 
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Originally Posted by bingofuel View Post
Please quote the legislation regarding this comment.
Depends where you are, but many countries have either Special Convoy Rights, or a general etiquette with regard to overtaking.

In the UK, the etiquette is to treat a military convoy as a single vehicle, but the convoy is required to drive with sufficient space between vehicles to allow an overtaking vehicle an emergency space to pull in to if required, for example to avoid oncoming traffic or to turn off at a left turn.

Such leniency is not the case in some other countries in Europe, where it is an offence to pull into the gaps between vehicles in a military convoy.

Here in the UK the military will normally set a convoy speed based on the slowest speed of the vehicle in the convoy; 55 mph is typical. Bear in mind that many military trucks are not designed for high speed on-road use, they are geared and equipped with tyres and suspension that is optimised for operation on rough tracks of off road.

One practical limit on convoy spacing can be the location of the rear convoy marker plates/white painted diff. If tucked well under the vehicle (as they often are) then that may mean the following driver has to stay well back, as he/she is normally required to keep the marker plate in view.
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Old 25th Apr 2017, 15:02   #19 (permalink)
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In the 80's I happened to be passing a very long and drawn-out British army convoy on the A12. The road was quiet and despite no joining traffic, every vehicle signalled and then moved from the inner to middle lane while passing joining points.

I imagine a lot of the procedure is based on them potentially carrying things that explode. Like Sergeants.
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Old 25th Apr 2017, 15:38   #20 (permalink)
 
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Why in this day and age do they need to be in convoy anyway? I could understand in a hostile environment such as Afghanistan or Iraq, but UK? Surely they can drive from A to B without someone leading them. Having regularly seen military vehicle broken down beside the road i suppose it is to rescue the laggards.
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