the nodding donkey:
From the facts presented, I deduct that lorry B was driven by a foreign driver, watching a movie on his laptop or using his phone, and lorry C was a box jockey driving three feet behind lorry B, on the limiter and cruise control.
Excellent work Holmes. Now stop dicking about on a forum and get back to foiling Moriarty.
Carryfast:
cav551:
You can forget what it says in the Highway code about stopping distances. Just how far a car or light truck will travel before it can stop. These have brakes capable of achieving near to 1G rate of deceleration. The pass figure for HGV brakes is 1/2G to begin with. Sobering thought about 56 mph converted into artic lengths.Realistically vehicle stopping distances are irrelevant in the case of anyone being presented with a vehicle/s ahead at or coming to a more or less dead stop which they hadn’t anticipated.Such as in the case of the video I posted previously.
The camera car in that video is following at a distance of about 30 metres. That is way too close for 70mph.
Roymondo:
The camera car in that video is following at a distance of about 30 metres. That is way too close for 70mph.
The point was that he also wasn’t reading the road ‘ahead’ of the vehicle in front. 
It’s doubtful that even the ‘recommended’ seperation distances will be guaranteed to provide sufficient vision to allow that.
Carryfast:
Roymondo:
The camera car in that video is following at a distance of about 30 metres. That is way too close for 70mph.The point was that he also wasn’t reading the road ‘ahead’ of the vehicle in front.
70 mph is 31 metres per second. Even following the “two second rule” he should have left double the distance he did as a minimum.
Roymondo:
70 mph is 31 metres per second. Even following the “two second rule” he should have left double the distance he did as a minimum.
Absolutely.
But as I said it’s also doubtful that even the two second rule would have provided the required vision and braking distance to stop in time for the parked traffic ahead of the car in front.Which was the key point in that case.Just as in the case of a truck ahead running into a parked vehicle and thereby coming to a dead stop.
Roymondo:
Carryfast:
cav551:
You can forget what it says in the Highway code about stopping distances. Just how far a car or light truck will travel before it can stop. These have brakes capable of achieving near to 1G rate of deceleration. The pass figure for HGV brakes is 1/2G to begin with. Sobering thought about 56 mph converted into artic lengths.Realistically vehicle stopping distances are irrelevant in the case of anyone being presented with a vehicle/s ahead at or coming to a more or less dead stop which they hadn’t anticipated.Such as in the case of the video I posted previously.
The camera car in that video is following at a distance of about 30 metres. That is way too close for 70mph.
I slowed the vid down to a frame by frame and have put some figures on, Camera car was doing 68mph and I make him 27metres behind giving a gap of 0.9 seconds, i think he was doing between 45 & 55 when he passed the stationary car. S he must have just got to his brakes
May be some credit to the bloke in the big van, from the moment the car began to swerve and the vans brake lights coming on was 0.4 seconds, (fastest reaction times are something like 0.75sec) so he did sort of predict what was about to happen.
Most vehicles only leave about a 1 second gap, leave more than that and someone else will soon fill the space. The 4 second gap often mentioned for HGVs is huge! at 56mph that would be 100m or 11 white lines!
A 4 second gap is not that huge! Drivers seem to be obsessed with preserving their position in the Motorway GP to the extent that easing off for a minute or two will somehow cause their ■■■■■ to shrink (or something equally serious).
If the vehicle in front was to crash into something and stop dead (OK It would probably would shunt it half an artic length) how far behind that vehicle would you need to be to come to a halt without touching it if going at 56 mph?
cav551:
If the vehicle in front was to crash into something and stop dead (OK It would probably would shunt it half an artic length) how far behind that vehicle would you need to be to come to a halt without touching it if going at 56 mph?
Going off the figures in your previous post regarding “G” if we assume that the truck can brake at 0.75g and give the driver a thinking time of 1 second then that would work out at 67.5metres, which would be a 2.7second gap at 56mph.
cav551:
If the vehicle in front was to crash into something and stop dead (OK It would probably would shunt it half an artic length) how far behind that vehicle would you need to be to come to a halt without touching it if going at 56 mph?
In a fully loaded 44T truck? Somewhere around 450ft - or over 5 seconds…
Roymondo:
A 4 second gap is not that huge! Drivers seem to be obsessed with preserving their position in the Motorway GP to the extent that easing off for a minute or two will somehow cause their ■■■■■ to shrink (or something equally serious).
As mentioned, on a busy motorway, or dual carriageway, I really don’t think you’d preserve a 4 second gap for that long without other drivers constantly pulling into it.
Bluey Circles:
Roymondo:
Carryfast:
cav551:
You can forget what it says in the Highway code about stopping distances. Just how far a car or light truck will travel before it can stop. These have brakes capable of achieving near to 1G rate of deceleration. The pass figure for HGV brakes is 1/2G to begin with. Sobering thought about 56 mph converted into artic lengths.Realistically vehicle stopping distances are irrelevant in the case of anyone being presented with a vehicle/s ahead at or coming to a more or less dead stop which they hadn’t anticipated.Such as in the case of the video I posted previously.
The camera car in that video is following at a distance of about 30 metres. That is way too close for 70mph.
I slowed the vid down to a frame by frame and have put some figures on, Camera car was doing 68mph and I make him 27metres behind giving a gap of 0.9 seconds, i think he was doing between 45 & 55 when he passed the stationary car. S he must have just got to his brakes
May be some credit to the bloke in the big van, from the moment the car began to swerve and the vans brake lights coming on was 0.4 seconds, (fastest reaction times are something like 0.75sec) so he did sort of predict what was about to happen.
Most vehicles only leave about a 1 second gap, leave more than that and someone else will soon fill the space. The 4 second gap often mentioned for HGVs is huge! at 56mph that would be 100m or 11 white lines!
Yes, less so with the 18t box van and the wagon with the static caravan on behind they should have had a fairly good view but if the original swerving car hadn’t got on to the hard shoulder they would have ploughed into the aftermath.
Roymondo:
cav551:
If the vehicle in front was to crash into something and stop dead (OK It would probably would shunt it half an artic length) how far behind that vehicle would you need to be to come to a halt without touching it if going at 56 mph?In a fully loaded 44T truck? Somewhere around 450ft - or over 5 seconds…
from 56mph (82 ft per sec) to stopping is an average speed of 41 ft/sec, so 5 seconds to stop would be 205 foot. (62.5m) which is pretty close to my guestimate of 67.5m.
I don’t see an HGV achieving .75G. More likely .5 G or just over.
cav551:
I don’t see an HGV achieving .75G. More likely .5 G or just over.
56mph, 0.5 G and 1 sec thinking time = 89 metres (288’)
Bluey Circles:
cav551:
I don’t see an HGV achieving .75G. More likely .5 G or just over.56mph, 0.5 G and 1 sec thinking time = 89 metres (288’)
This would be about as good as it gets and that’s astonishing for a five axle 40 tonner. 
In which case it’s then mostly about adding the reaction time that gets taken out by a sudden dead stop type situation ahead.Or how close the vehicle is to hidden stopped traffic ahead of the vehicle in front when braking begins.
Here is a video that I have found of which I presume is a real life situation. It is a good quaulity video and as it is at a junction with good road markings I have been able to put some meaningful numbers onto it. If road markings are accurately painted onto the road and digital cameras precisely take 30 pictures a second then my figures could have some rough accuracies, It is a great pity I don’t know how heavy the camera lorry was or how many axles, it could be two axles at 18 ton or an empty artic with 6 axles running at 17 ton. disc or drum ?
The figures I have come up with are not as good as I had expected. From 50 mph, 27 metres thinking time then possibly another 63 metres stopping time (I know it didnt stop but that would have been hos stopping distance had he continued braking at the same rate see dotted projection line) And that rate of deceleration would only represent 0.4 g a good bit lower than suggested earlier in the thread and nearly half of my guess of 0.75g.
FFS - I used to go out on a friday night, drink pints and chase women …
Bluey Circles:
https://www.youtube.com/watch?v=V_McnjNGq-A
The real question is the thought process going on the heads of these ‘drivers’ which just seems alien to me. 
At that point I’m thinking the seperation distance has eroded to suicidal levels and as part of that what might be hidden ahead of the truck in front having taken out any visibility available ahead of it at 0.02.That then all so predictably had to anchor up because of a developing situation ahead of it from the slip road etc which itself probably could have been anticipated before it happened.IE all the technology and foolproof braking ability in the world won’t compensate for non existent levels of anticipation and equally non existent seperation distances removing visibility and reaction time.
the maoster:
the nodding donkey:
From the facts presented, I deduct that lorry B was driven by a foreign driver, watching a movie on his laptop or using his phone, and lorry C was a box jockey driving three feet behind lorry B, on the limiter and cruise control.Excellent work Holmes. Now stop dicking about on a forum and get back to foiling Moriarty.
Shouldn’t Robroy have posted by now about some people coming back in too early without a flash?
Even though I do agree, and if truck B had deprived truck C of forward viability, is truck C still to blame?
I’d say " f"@& glad I weren’t involved in that" and crack on lol
