Another NIP - A depressing experience
Discussion
If I am interject as politely as possible, may I with humility and with deep regret, utter with a humble and sincere voice that:
It is a little more complicated .
Technically kinetic energy is a factor, it depends on the weight of the object being hit and its resistance to movement/ability to absorb the energy of the impacting object and if it has the mass to deflect the impacting object.
A 21st person will absorb more than a small child as tissue types are both deformidable in differing ways and jointed sections carry differing weights.
A 21st person will have a higher ability to deflect the impacting object when their mass is closer, eg a M'Bike or cycle.
So, being hit by a truck (which greatly exceeds the 21st body's ability to deflect its path has differing damage to one being hit by a Bike. The 21st body is not a fixed object either and has a mass that can deflect the M'Bike's kinetic energy deflecting its path of travel and thus the transfer of its kenetic energy to deeper tissues.
A 4st body's ability is less able to do this.
Is it significant ?
Yes it is, the energy is absorbed by the object being hit, be that bone, soft tissue etc to a critical point before damage or change of direction is what primarily dictates the type of injury revived.
Big guy dead tackles another big guy, their mass cancels it self out and the stop on the point of impact with a crutch !
or
Big guy tackles a small guy, drive thru him (partly by the kinetic energy) and buries him 5 yards back.
Other factors such as angle of attack, resilience of the material/possible deflection angles balh blah.....after that factors such as tissue strength and elasticity blah blah. start to make larger variations.
There is a point when the flesh will liquidate/fracture as the pressure builds up and will explode/fracture the cells in the area of maximum transfer or compression to the point of accelerating it along the same path of travel of the impacting object. (head bounces on a bonnet in a low speed impact)
The effect would be similar with any penetrating object and be less dependent of bus/car/bike type as all exceed that maximum point by large margin if the shape of the object concentrates in that area. (naturally there are large variations here that would take pages to discuss.
Edited by Stickyfinger on Saturday 29th August 15:00
Edited by Stickyfinger on Saturday 29th August 15:00
Pete317 said:
Agree it's more complicated.
However, a collision with even a 21st person is not going to deflect a 1-ton car much more than it would a 10-ton bus.
It will however deflect the crash padding/Flex zones more on the bonnets etc of modern cars, a similar result of slowing the speed decrease reducing the "hard stop", still endless variables all of which can make a difference to the end result....but not always I agree.However, a collision with even a 21st person is not going to deflect a 1-ton car much more than it would a 10-ton bus.
To add balance, i got caught doing 37 in a 30 (or was it 38, i can't remember) and attended a speed awareness course in west sussex. There attitude was pretty much "We speed, you speed, everyone speeds, you got caught... here are some reasons why it might be a good idea to be more aware of your speed"
I will agree with you though that noone seems to know what a dual carriageway is.
I will agree with you though that noone seems to know what a dual carriageway is.
anonymous said:
[redacted]
In brief: safety totalitarians like to mention KE but it isn't conserved in a collision between a deformable vehicle and a squidgy human so it's the wrong thing to be looking at, and it's not directly proportional to v it's proportional to v^2 which is precisely the attraction of making that mistake.Stickyfinger said:
Pete317 said:
Agree it's more complicated.
However, a collision with even a 21st person is not going to deflect a 1-ton car much more than it would a 10-ton bus.
It will however deflect the crash padding/Flex zones more on the bonnets etc of modern cars, a similar result of slowing the speed decrease reducing the "hard stop", still endless variables all of which can make a difference to the end result....but not always I agree.However, a collision with even a 21st person is not going to deflect a 1-ton car much more than it would a 10-ton bus.
A car travelling at 30mph will have a seemingly impressive KE value but that KE won't get transferred to a pedestrian in a collision or they would behave very differently to what actually happens. Given other PHers may or may not have had the misfortune to witness a collision, this will soon become obvious, if it wasn't already obvious.
To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
turbobloke said:
A car travelling at 30mph will have a seemingly impressive KE value but that KE won't get transferred to a pedestrian in a collision or they would behave very differently to what actually happens. Given other PHers may or may not have had the misfortune to witness a collision, this will soon become obvious, if it wasn't already obvious.
To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
If not the kinetic energy dissipating thru tissue surface areas (and continuing to the more dense structures if large enough), what causes the extensive compression/rupture injury's often seen in a Vech/Ped RTA then ?To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
Stickyfinger said:
turbobloke said:
A car travelling at 30mph will have a seemingly impressive KE value but that KE won't get transferred to a pedestrian in a collision or they would behave very differently to what actually happens. Given other PHers may or may not have had the misfortune to witness a collision, this will soon become obvious, if it wasn't already obvious.
To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
If not the kinetic energy dissipating thru tissue surface areas (and continuing to the more dense structures if large enough), what causes the extensive compression/rupture injury's often seen in a Vech/Ped RTA then ?To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
Only a small fraction of the kinetic energy is actually dissipated by the collision - the car, unless braked, continues to move at almost the same speed after the collision, meaning that it still possesses nearly all of its pre-collision KE.
The amount of KE transferred to the pedestrian is determined by the delta velocity and mass of the pedestrian.
Edited by Pete317 on Saturday 29th August 20:56
Stickyfinger said:
turbobloke said:
A car travelling at 30mph will have a seemingly impressive KE value but that KE won't get transferred to a pedestrian in a collision or they would behave very differently to what actually happens. Given other PHers may or may not have had the misfortune to witness a collision, this will soon become obvious, if it wasn't already obvious.
To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
If not the kinetic energy dissipating thru tissue surface areas (and continuing to the more dense structures if large enough), what causes the extensive compression/rupture injury's often seen in a Vech/Ped RTA then ?To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
Try Ft = mv - mu (impulse equal to change in momentum).
It's got much more to offer.
Looking at a fall onto partly yielding ground from about 9 metres, impact speed approx 30 mph, the nature of partial restraint on internal organs means they'll carry on moving for a short time at close to the impact speed and stop abruptly when they hit something e.g. the rib cage. The rapid stop from a decent speed in a small time corresponds to a large force (F is proportional to the lost momentum, and to 1/t) and a large force will tear tissue. If in a bodily collision with a car the pedestrian's head then impacts with the kerb afterwards, a similar event albeit at lower speeed will happen to the brain moving against the skull. Clearly neither of these events does anyone any good.
I've been using my trusty fag packet for calculations, anyone is free to check them, please let me know if it needs a service.
Pete317 said:
It is kinetic energy, but that's beside the point.
Only a small fraction of the kinetic energy is actually dissipated by the collision - the car continues to move at much the same speed after the collision, meaning that it still possesses nearly all of its pre-collision KE.
The amount of KE transferred to the pedestrian is determined by the delta speed of the pedestrian and the mass of the pedestrian.
Yes I know that. Less is transferred by a truck and more from a M'Bike then cycle, which is my point.Only a small fraction of the kinetic energy is actually dissipated by the collision - the car continues to move at much the same speed after the collision, meaning that it still possesses nearly all of its pre-collision KE.
The amount of KE transferred to the pedestrian is determined by the delta speed of the pedestrian and the mass of the pedestrian.
turbobloke said:
Stickyfinger said:
turbobloke said:
A car travelling at 30mph will have a seemingly impressive KE value but that KE won't get transferred to a pedestrian in a collision or they would behave very differently to what actually happens. Given other PHers may or may not have had the misfortune to witness a collision, this will soon become obvious, if it wasn't already obvious.
To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
If not the kinetic energy dissipating thru tissue surface areas (and continuing to the more dense structures if large enough), what causes the extensive compression/rupture injury's often seen in a Vech/Ped RTA then ?To take an example, a 2 tonne BMW (2000 kg) travelling at 30mph (13.4 m/s) represents 180 kilojoules of KE as near as dammit and if that 180 kJ of KE was transferred to a 50 kg pedestrian in a collision then in the instant immediately afterwards the car would be stationary and the pedestrian would be travelling at just under 85 m/s which is 190 mph.
That's clearly not what happens in a 30 mph collision between a hefty BMW and a pedestrian, nowhere near it. The calculated KE is not transferred, so why bother calculating it...considering the KE of the car makes the speed aspect look scarier because KE varies as v^2 but it's not a useful approach.
It may not be wise to point this out on one of those courses, and definitely not in a text message.
Try Ft = mv - mu (impulse equal to change in momentum).
It's got much more to offer.
Looking at a fall onto partly yielding ground from about 9 metres, impact speed approx 30 mph, the nature of partial restraint on internal organs means they'll carry on moving for a short time at close to the impact speed and stop abruptly when they hit something e.g. the rib cage. The rapid stop from a decent speed in a small time corresponds to a large force (F is proportional to the lost momentum, and to 1/t) and a large force will tear tissue. If in a bodily collision with a car the pedestrian's head then impacts with the kerb afterwards, a similar event albeit at lower speeed will happen to the brain moving against the skull. Clearly neither of these events does anyone any good.
I've been using my trusty fag packet for calculations, anyone is free to check them, please let me know if it needs a service.
jimmy156 said:
To add balance, i got caught doing 37 in a 30 (or was it 38, i can't remember) and attended a speed awareness course in west sussex. There attitude was pretty much "We speed, you speed, everyone speeds, you got caught... here are some reasons why it might be a good idea to be more aware of your speed"
I will agree with you though that noone seems to know what a dual carriageway is.
I've been on two SACs. The first one was great, the bloke was an ex-copper who seemed fair and understood that some people might learn something and that we were all normal people taking a day off work to save ourselves from 3 points for silly mistakes (not checking for a camera van where there sometimes is one).I will agree with you though that noone seems to know what a dual carriageway is.
The second one seemed like a right wotsit. He had such an attitude that, yes fair enough we were "criminals", but that driving at 36 in a 30 is akin to going on a rape spree at a Catholic girls school.
I feel that it was totally safe to do 40mph on a dual carriageway with a big divider in the middle with two sets of armco barriers but it's a 30 because there's a ped crossing at one point (incredible visibility so impossible to miss at 40, 50 or even 60!). Them's the rules tho so I don't mind paying £100 for not paying enough attention in spotting camera vans.
OP, just drop the sense of superiority when you go to a SAC. Driving and cars are one of your hobbies if you're on PH. I'm sure if you went to a gardening awareness course you would be the one mocked as a pleb for not being able to tell a fern from an alfalfa etc.
charltjr said:
So to boil your post right down, you broke the law and got caught, but it's not fair because you don't agree with the law, and other drivers who also broke the law and got caught aren't as aware of the rules of the road as you are and were in dire need of some education?
Which is, just maybe, why the SACs exist?
I know, it's a radical thought.
[sarcastic mode]Which is, just maybe, why the SACs exist?
I know, it's a radical thought.
SACS exist(IMHO) in all simplicity to keep the good ship SCP financially afloat.( A lot of the following is speculation, but looking at the history, JUST how close to the truth is it ?)
In the beginning , SCP got funded by expenses from the Fixed Penalties they brought in. But then , the bean counters at SCP HQ got busy and found various ways to "milk " the expenses ( sounds familiar ?). All was well till the treasury found out and the great god of the financial and government world Gordo decided that in future this would cease and LA would be given a road safety allowance,and SCP would be funded out of this. With the empire crumbling (and a lot of long term/high ranking traffic etc officers being made redundant) an idea formed in ACPO HQ- lets get in on the "road safety act"- we need to have education -let's use the skills of the blokes on pension to help them mete out their more than generous redundancy and pension settlements and keep them off the unemployment register. Then the SCP can run these courses and cream off the profits rather than HMG getting the fines.
Now, if we could just have PAC/CAC(pedestrian/cycling awareness courses), just think how safe our roads could become. After all ,what is missing on our safest roads aka motorways- coconut to the right answer, which is NO PEDS or cyclists.
[/sarcastic mode]
The daft thing with SAC's is it's the wrong sort of people who get sent on them. It's generally older people who are driving to the conditions rather than the limit - young drivers are (usually) smart enough not to get caught in such a way.
It's the people in the fixed penalty bracket who would probably mostly benefit.
Sometimes it's nothing to do with safety at all - colleague did an SAC after being caught at 46 when the M42 variable was set to 40 early one morning. Half the people on the course had been caught the same way. That's traffic management, not safety.
It's the people in the fixed penalty bracket who would probably mostly benefit.
Sometimes it's nothing to do with safety at all - colleague did an SAC after being caught at 46 when the M42 variable was set to 40 early one morning. Half the people on the course had been caught the same way. That's traffic management, not safety.
Sheepshanks said:
Sometimes it's nothing to do with safety at all - colleague did an SAC after being caught at 46 when the M42 variable was set to 40 early one morning. Half the people on the course had been caught the same way. That's traffic management, not safety.
I would get the thoughts of the guys who work on those roadworks before you dismiss it as "road management"We forget, speed limits are NOT to control OUR speed, they are to ensure that when we fall off the road for whatever reason, we are doing so at speeds that go a long way to protects any workers present, or we go thru missing barriers into three lanes of oncoming traffic.....so not about controlling us more protecting them from our metal object when it goes wrong.
Variable speed limits within a section of works is a recipe for disaster unless it is to increase it towards an open works free road..........you could say .... Hi-Lo-Hi-Lo is a No No.
.....sorry
Edited by Stickyfinger on Sunday 30th August 15:28
Stickyfinger said:
Sheepshanks said:
Sometimes it's nothing to do with safety at all - colleague did an SAC after being caught at 46 when the M42 variable was set to 40 early one morning. Half the people on the course had been caught the same way. That's traffic management, not safety.
I would get the thoughts of the guys who work on those roadworks before you dismiss it as "road management"We forget, speed limits are NOT to control OUR speed, they are to ensure that when we fall off the road for whatever reason, we are doing so at speeds that go a long way to protects any workers present, or we go thru missing barriers into three lanes of oncoming traffic.....so not about controlling us more protecting them from our metal object when it goes wrong.
Variable speed limits within a section of works is a recipe for disaster unless it is to increase it towards an open works free road..........you could say .... Hi-Lo-Hi-Lo is a No No.
.....sorry
Edited by Stickyfinger on Sunday 30th August 15:28
The variable limits on the M42 are for traffic management.
I'll no doubt get criticised for this point of view but I can see where the OP is coming from.
Nearly 3 years ago I picked up 3 points in Wales. The wife and I were having a long weekend driving and walking in Wales as a sort of last hurrah before she became too pregnant for that sort of thing. We spent 4 days going from the Severn crossing to Great Orme, taking mainly back routes so we could stop and walk and generally enjoy it, and also enjoy some fairly demanding driving without exceeding speed limits. Over the 4 days we didn't break a limit by more than a couple of mph, and had a really nice time. On the sunday we drove back taking the A5, and I got pinged by a mobile van on the 3-lane Dinmael stretch at 80 mph (recorded speed), mid-overtake (having followed the gent for 10-15 miles and 20 mins or so, doing the 35-40 mph plod that we hear about very often).
So I was bang to rights and took the £60 penalty and 3 points, and it didn't actually affect my insurance at all. No increase in premium, anyway. I was reminded to move even further offside and take a good look for vans, especially at prime overtaking locations. What annoyed me was this:
During the overtake, I was followed closely by another gent. There were two oncomers, one was past by the time I moved out to the launch position, the other was distant and not involved. Of the three cars involved, there was me exceeding the limit temporarily while completing the pass; the overtakee who had accelerated during the pass, either out of ignorance or a deliberate attempt to block; and the guy tailgating me during an overtake while speeding.
If we are to believe that the cameras are for safety, how is it justifiable that the person temporarily speeding during an overtake, on a stretch of road designed to facilitate overtaking, gets penalised - rightly, I can accept - but the other two don't? One who is either not cooperating with an overtake or not paying attention, and one who is both speeding and tailgating?
I've not done a course so can't comment on that, but do have some empathy with the guy for getting nabbed for a temporary transgression, especially when others around at the same time were doing the same or worse.
As Mr Dennis may put it, where's the consistency?
Nearly 3 years ago I picked up 3 points in Wales. The wife and I were having a long weekend driving and walking in Wales as a sort of last hurrah before she became too pregnant for that sort of thing. We spent 4 days going from the Severn crossing to Great Orme, taking mainly back routes so we could stop and walk and generally enjoy it, and also enjoy some fairly demanding driving without exceeding speed limits. Over the 4 days we didn't break a limit by more than a couple of mph, and had a really nice time. On the sunday we drove back taking the A5, and I got pinged by a mobile van on the 3-lane Dinmael stretch at 80 mph (recorded speed), mid-overtake (having followed the gent for 10-15 miles and 20 mins or so, doing the 35-40 mph plod that we hear about very often).
So I was bang to rights and took the £60 penalty and 3 points, and it didn't actually affect my insurance at all. No increase in premium, anyway. I was reminded to move even further offside and take a good look for vans, especially at prime overtaking locations. What annoyed me was this:
During the overtake, I was followed closely by another gent. There were two oncomers, one was past by the time I moved out to the launch position, the other was distant and not involved. Of the three cars involved, there was me exceeding the limit temporarily while completing the pass; the overtakee who had accelerated during the pass, either out of ignorance or a deliberate attempt to block; and the guy tailgating me during an overtake while speeding.
If we are to believe that the cameras are for safety, how is it justifiable that the person temporarily speeding during an overtake, on a stretch of road designed to facilitate overtaking, gets penalised - rightly, I can accept - but the other two don't? One who is either not cooperating with an overtake or not paying attention, and one who is both speeding and tailgating?
I've not done a course so can't comment on that, but do have some empathy with the guy for getting nabbed for a temporary transgression, especially when others around at the same time were doing the same or worse.
As Mr Dennis may put it, where's the consistency?
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