Who done it?
It may not be politically correct to suggest that motorcyclists often are responsible for their own injuries, at least not here (we shall see), but I thought as an introduction to my way of thinking I would post a bit of a who done it and see if you agree or not with my findings.
A motorcyclist is riding on a one-way street in the middle of town near
where she lives. She has ridden her bike along this street hundreds of
times in the past. It is well familiar to her.
As she approaches an intersection, another one-way street, where there are stop signs
preventing traffic from entering from her right - she has the right of
way - and she knows from experience that it is not a busy intersection.
She finally notices a car easing its way into the intersection.
Shortly thereafter she died - after she collided with that car.
Speed limit on the street she was riding on was 30 mph. The crush damage to
the vehicle and motorcycle suggest an impact speed of about 40 mph. She
left a 40 foot skid mark before the collision.
Oh, did I happen to mention that there was a double-parked delivery truck near the
intersection on her right side? Witnesses, including the driver of the
car, claimed that the truck obscured sight lines.
The driver of the car was uninsured.
The estate of the deceased hired an attorney seeking monetary relief. After
all, the lady died and "it wasn't her fault". So what if the driver of
the car she struck was uninsured?
You guessed it - they sued the trucking company claiming that their double-parked truck caused this
accident. The trucking company, after all, had 'deep pockets' and
nobody else did.
Do you agree?
Witnesses agreed that the car properly stopped at the stop sign then inched forward until it was
almost all the way across the intersection.
Other witnesses disagreed about the presence of the double-parked truck. Some placed it
five miles away from that intersection at the time of the accident,
based on GPS data recorded by the company. Others said the truck had
been there earlier than the accident. Still others said that the truck
was definitely there at the time of the accident.
Most states have laws which allow for contributory negligence to be determined and
affect monetary compensation. If, for example, the trucking company can
show that its negligence in the matter, if any, was less than 50%, it
is possible that it would not be liable for any financial costs.
What did the police who investigated this accident have to say? Well, they
wrote a ticket to the driver of the car for failing to yield the right
of way. They did not see a double parked truck at the scene but they
documented that witnesses claimed such a truck had been there at the
time of the accident.
Should the trucking company be held liable for this ladies death?
Let's first talk about the driver of the car she ran into. Its driver could
not see traffic at all from his position at the stop line near the stop
sign. He stopped. Then he moved very cautiously into the intersection.
What else could he do? Should he have remained stopped until the
double-parked truck, if it was actually there, moved out of the way? If
his wait had lasted an hour, should he have been required to remain in
place still longer?
He certainly DID fail to yield the right of way. His ticket was 'righteous'. But it was unintentional and there
were extenuating circumstances that any jury would understand. When he
finally did see the motorcycle it was too late for him to do anything
to avoid the collision. Even if he did have insurance, was it likely
that it would pay handsomely because of the death of the rider? Well,
that goes back to the issue of contributory negligence, doesn't it?
So now it's time to look at the motorcyclist's responsibility in this
matter. We learn that she was properly licensed (had a motorcycle
endorsement on her license) and that she had taken and passed an MSF
class. We begin being critical by acknowledging that she was driving
too fast. She was traveling at least 40 mph when she crashed and it was
a 30 mph zone. But just how important was that in the bigger scheme of
things? I mean, had that double-parked truck not been there, then the
accident probably would not have happened at all, right? So what if she
was speeding a little bit, just like you and I do every time we drive
or ride?
Time, I guess, to look at some details. Let's start with that skid mark.
It was 40 foot long. Obviously that means that the rider noticed the car
when she was traveling faster than the speed of impact because she
scrubbed some speed during that skid. But how much faster?
The police determined that the Dynamic Coefficient of Friction between the
bike's tires and the roadway was 0.79. No grade, no rain or ice on the
ground, middle of the afternoon with good lighting and no weather
issues.
How much speed is scrubbed during a 40 foot skid under those conditions?
Pay attention here, please. A skid mark does not tell you how fast a person
was traveling during that skid. The skid mark ONLY tells you that a
certain amount of energy was transformed during the skid. That is, a
certain amount of kinetic (moving) energy was converted into heat
during the skid. It doesn't matter how fast the person was going during
the skid - essentially the same amount of energy is converted
regardless of speed. The faster you go, the less time it takes to scrub
that energy, but the amount of energy converted is essentially the same.
But we do know some other things about a skid mark other than its length.
We know that it results from a locked brake and a skidding tire, and
that a brake does not lock by itself, normally. That is, it took an
effort on the part of the biker to lock her brake. By the way, we also
know that it is almost always true that a skid mark is from the rear
tire of a motorcycle because if it is from the front tire, the bike
loses all control and quickly ends up on its side.
Ever heard of PDR? That stands for Perception, Decision, Reaction time. Before you
can lock your brake(s) you must first perceive a need to do so, decide
to do so, then move your hands and feet to the levers as a reaction to
a threat. The amount of time it takes to do that is called PDR time
(or, in some places, simply PR time).
Tests have been conducted that document that professional riders who KNOW that a threat is about
to present itself (a signal light is about to change colors, for
example) CAN have a PDR as low as 0.2 to 0.3 seconds!!! However, those
same riders take on average about 1.5 seconds of PDR when a threat is
not anticipated (a car ahead suddenly begins skidding its tires).
Indeed, about 70% of all motorists take about 1.5 seconds to begin
applying their brakes when a threat is NOT anticipated.
We can assume, therefore, that the lady riding her bike that day took about 1.5 seconds to begin applying her brakes.
Well, there is a little more reason to support that assumption. You see,
witnesses claimed that she had been stunting her bike prior to the
accident. That is, she had just done a wheelie, and when she came off
that wheelie she began accelerating. You MUST conclude that she did NOT anticipate the presence of a threat at the time.
So, now what do we know about how fast she was going before she began her
skid? We actually have enough information to make that call, but we
want something else to increase our confidence in it. Fortunately, we
recall that witnesses claimed to have seen her going between 30 mph and
50 mph just before she crashed. Since we have very good reason to
believe that she was going at least 40 mph when she did crash, we know
that the low end of those witness estimates was too low. She had to
have been traveling in excess of 40 mph before she started skidding,
but if the witness estimate was believable, she could not have been
traveling more than 50 mph. In other words we have excellent reason to
believe that she was traveling at about 45 mph before she began her
skid.
Can we confirm that with the skid length evidence? You bet.
A skid would be 40 feet long if the rider used 100% braking efficiency
(i.e., both brakes maximally applied) and came to a dead stop (without
a collision), if she started skidding at just under 31 mph.
Where:
'v' = velocity at start of skid
'f' = drag factor
'd' = Skid mark distance
The drag factor (f) is
Where:
'u' = Coefficient of Friction
'n' = braking efficiency
Since grade = 0 ...
v = 30 * 0.79 * 1.00 * 40
v = 30.79 mph
Had the braking efficiency been 60%, v would equal 23.85 mph.
(This value (v) shall henceforth be called the 'energy equivalent speed'. It
is the Kinetic energy converted to heat during a 40 foot skid, no
matter how fast we are moving when we start the skid, assuming a given
drag factor.)
Since there was only one skid mark it is not possible that she used 100% braking efficiency. Had she used only her
rear brake she would have been able to attain no more than 40% braking
efficiency as at that point she would have transferred virtually all
the weight off her rear tire and no more braking was possible. Because
she was faced with an imminent collision we can assume that she used at
least SOME front brake along with her rear brake. Since the MSF tests
braking skills to determine if even a rank amateur (newbie) can achieve
a 60% braking efficiency, we can be confident that she used at least
60% and less than 100% braking efficiency during her skid. To be
conservative, we will estimate that she used 60%.
It is easy to calculate that if she used 60% braking efficiency, she had to have been
traveling at just under 47 mph at the start of her skid. Obviously, the
greater her braking skills, the faster she was traveling when she began
skidding, but we took a conservative approach to this analysis.
Vstart = Velocity at the start of the skid
Vscrubbed = Energy equivalent speed
Vcollision = Velocity at end of skid
Vstart = 46.6 mph
It is entirely proper and defensible, assuming rounding of numbers, to
conclude that she was traveling at no less than 47 mph before she began
her skid.
In other words, her 40 foot skid scrubbed approximately 7 mph off her speed.
Now we have enough data. Using a 1.5 second PDR and a speed of 47 mph, we
know that the lady traveled 103 feet before her skid started. That
means that the lady FIRST NOTICED the car in the intersection when she
was 143 feet away from it (40 + 103).
We just learned an interesting fact: Had the car driver simply crossed the
intersection at normal speed instead of creeping along, since she
crashed into his car near its rear, the accident would not have
happened. That is, had the car driver acted irrationally, there would
not have been an accident. Yeah, but so what? He did act rationally and
the accident did happen.
Well, doing a 'what if' makes a lot of sense when trying to determine proportionate negligence, as I'll now show you.
What if the motorcyclist had been traveling at or below the speed limit?
We know that no matter what her speed was before she locked her brake, she
could and did see the car when she was 143 feet away from it.
If she had been traveling at 30 mph, then she would have traveled 66 feet
before her skid began. That means that she would begin skidding 77 feet
from the car. And that means that she would NOT HAVE COLLIDED as she
would have come to a dead stop within 63 feet, or 14 feet shy of
hitting the car.
A motorcyclist is riding on a one-way street in the middle of town near
where she lives. She has ridden her bike along this street hundreds of
times in the past. It is well familiar to her.
As she approaches an intersection, another one-way street, where there are stop signs
preventing traffic from entering from her right - she has the right of
way - and she knows from experience that it is not a busy intersection.
She finally notices a car easing its way into the intersection.
Shortly thereafter she died - after she collided with that car.
Speed limit on the street she was riding on was 30 mph. The crush damage to
the vehicle and motorcycle suggest an impact speed of about 40 mph. She
left a 40 foot skid mark before the collision.
Oh, did I happen to mention that there was a double-parked delivery truck near the
intersection on her right side? Witnesses, including the driver of the
car, claimed that the truck obscured sight lines.
The driver of the car was uninsured.
The estate of the deceased hired an attorney seeking monetary relief. After
all, the lady died and "it wasn't her fault". So what if the driver of
the car she struck was uninsured?
You guessed it - they sued the trucking company claiming that their double-parked truck caused this
accident. The trucking company, after all, had 'deep pockets' and
nobody else did.
Do you agree?
Witnesses agreed that the car properly stopped at the stop sign then inched forward until it was
almost all the way across the intersection.
Other witnesses disagreed about the presence of the double-parked truck. Some placed it
five miles away from that intersection at the time of the accident,
based on GPS data recorded by the company. Others said the truck had
been there earlier than the accident. Still others said that the truck
was definitely there at the time of the accident.
Most states have laws which allow for contributory negligence to be determined and
affect monetary compensation. If, for example, the trucking company can
show that its negligence in the matter, if any, was less than 50%, it
is possible that it would not be liable for any financial costs.
What did the police who investigated this accident have to say? Well, they
wrote a ticket to the driver of the car for failing to yield the right
of way. They did not see a double parked truck at the scene but they
documented that witnesses claimed such a truck had been there at the
time of the accident.
Should the trucking company be held liable for this ladies death?
Let's first talk about the driver of the car she ran into. Its driver could
not see traffic at all from his position at the stop line near the stop
sign. He stopped. Then he moved very cautiously into the intersection.
What else could he do? Should he have remained stopped until the
double-parked truck, if it was actually there, moved out of the way? If
his wait had lasted an hour, should he have been required to remain in
place still longer?
He certainly DID fail to yield the right of way. His ticket was 'righteous'. But it was unintentional and there
were extenuating circumstances that any jury would understand. When he
finally did see the motorcycle it was too late for him to do anything
to avoid the collision. Even if he did have insurance, was it likely
that it would pay handsomely because of the death of the rider? Well,
that goes back to the issue of contributory negligence, doesn't it?
So now it's time to look at the motorcyclist's responsibility in this
matter. We learn that she was properly licensed (had a motorcycle
endorsement on her license) and that she had taken and passed an MSF
class. We begin being critical by acknowledging that she was driving
too fast. She was traveling at least 40 mph when she crashed and it was
a 30 mph zone. But just how important was that in the bigger scheme of
things? I mean, had that double-parked truck not been there, then the
accident probably would not have happened at all, right? So what if she
was speeding a little bit, just like you and I do every time we drive
or ride?
Time, I guess, to look at some details. Let's start with that skid mark.
It was 40 foot long. Obviously that means that the rider noticed the car
when she was traveling faster than the speed of impact because she
scrubbed some speed during that skid. But how much faster?
The police determined that the Dynamic Coefficient of Friction between the
bike's tires and the roadway was 0.79. No grade, no rain or ice on the
ground, middle of the afternoon with good lighting and no weather
issues.
How much speed is scrubbed during a 40 foot skid under those conditions?
Pay attention here, please. A skid mark does not tell you how fast a person
was traveling during that skid. The skid mark ONLY tells you that a
certain amount of energy was transformed during the skid. That is, a
certain amount of kinetic (moving) energy was converted into heat
during the skid. It doesn't matter how fast the person was going during
the skid - essentially the same amount of energy is converted
regardless of speed. The faster you go, the less time it takes to scrub
that energy, but the amount of energy converted is essentially the same.
But we do know some other things about a skid mark other than its length.
We know that it results from a locked brake and a skidding tire, and
that a brake does not lock by itself, normally. That is, it took an
effort on the part of the biker to lock her brake. By the way, we also
know that it is almost always true that a skid mark is from the rear
tire of a motorcycle because if it is from the front tire, the bike
loses all control and quickly ends up on its side.
Ever heard of PDR? That stands for Perception, Decision, Reaction time. Before you
can lock your brake(s) you must first perceive a need to do so, decide
to do so, then move your hands and feet to the levers as a reaction to
a threat. The amount of time it takes to do that is called PDR time
(or, in some places, simply PR time).
Tests have been conducted that document that professional riders who KNOW that a threat is about
to present itself (a signal light is about to change colors, for
example) CAN have a PDR as low as 0.2 to 0.3 seconds!!! However, those
same riders take on average about 1.5 seconds of PDR when a threat is
not anticipated (a car ahead suddenly begins skidding its tires).
Indeed, about 70% of all motorists take about 1.5 seconds to begin
applying their brakes when a threat is NOT anticipated.
We can assume, therefore, that the lady riding her bike that day took about 1.5 seconds to begin applying her brakes.
Well, there is a little more reason to support that assumption. You see,
witnesses claimed that she had been stunting her bike prior to the
accident. That is, she had just done a wheelie, and when she came off
that wheelie she began accelerating. You MUST conclude that she did NOT anticipate the presence of a threat at the time.
So, now what do we know about how fast she was going before she began her
skid? We actually have enough information to make that call, but we
want something else to increase our confidence in it. Fortunately, we
recall that witnesses claimed to have seen her going between 30 mph and
50 mph just before she crashed. Since we have very good reason to
believe that she was going at least 40 mph when she did crash, we know
that the low end of those witness estimates was too low. She had to
have been traveling in excess of 40 mph before she started skidding,
but if the witness estimate was believable, she could not have been
traveling more than 50 mph. In other words we have excellent reason to
believe that she was traveling at about 45 mph before she began her
skid.
Can we confirm that with the skid length evidence? You bet.
A skid would be 40 feet long if the rider used 100% braking efficiency
(i.e., both brakes maximally applied) and came to a dead stop (without
a collision), if she started skidding at just under 31 mph.
Where:
'v' = velocity at start of skid
'f' = drag factor
'd' = Skid mark distance
The drag factor (f) is
Where:
'u' = Coefficient of Friction
'n' = braking efficiency
Since grade = 0 ...
v = 30 * 0.79 * 1.00 * 40
v = 30.79 mph
Had the braking efficiency been 60%, v would equal 23.85 mph.
(This value (v) shall henceforth be called the 'energy equivalent speed'. It
is the Kinetic energy converted to heat during a 40 foot skid, no
matter how fast we are moving when we start the skid, assuming a given
drag factor.)
Since there was only one skid mark it is not possible that she used 100% braking efficiency. Had she used only her
rear brake she would have been able to attain no more than 40% braking
efficiency as at that point she would have transferred virtually all
the weight off her rear tire and no more braking was possible. Because
she was faced with an imminent collision we can assume that she used at
least SOME front brake along with her rear brake. Since the MSF tests
braking skills to determine if even a rank amateur (newbie) can achieve
a 60% braking efficiency, we can be confident that she used at least
60% and less than 100% braking efficiency during her skid. To be
conservative, we will estimate that she used 60%.
It is easy to calculate that if she used 60% braking efficiency, she had to have been
traveling at just under 47 mph at the start of her skid. Obviously, the
greater her braking skills, the faster she was traveling when she began
skidding, but we took a conservative approach to this analysis.
Vstart = Velocity at the start of the skid
Vscrubbed = Energy equivalent speed
Vcollision = Velocity at end of skid
Vstart = 46.6 mph
It is entirely proper and defensible, assuming rounding of numbers, to
conclude that she was traveling at no less than 47 mph before she began
her skid.
In other words, her 40 foot skid scrubbed approximately 7 mph off her speed.
Now we have enough data. Using a 1.5 second PDR and a speed of 47 mph, we
know that the lady traveled 103 feet before her skid started. That
means that the lady FIRST NOTICED the car in the intersection when she
was 143 feet away from it (40 + 103).
We just learned an interesting fact: Had the car driver simply crossed the
intersection at normal speed instead of creeping along, since she
crashed into his car near its rear, the accident would not have
happened. That is, had the car driver acted irrationally, there would
not have been an accident. Yeah, but so what? He did act rationally and
the accident did happen.
Well, doing a 'what if' makes a lot of sense when trying to determine proportionate negligence, as I'll now show you.
What if the motorcyclist had been traveling at or below the speed limit?
We know that no matter what her speed was before she locked her brake, she
could and did see the car when she was 143 feet away from it.
If she had been traveling at 30 mph, then she would have traveled 66 feet
before her skid began. That means that she would begin skidding 77 feet
from the car. And that means that she would NOT HAVE COLLIDED as she
would have come to a dead stop within 63 feet, or 14 feet shy of
hitting the car.
Replies to This Discussion
-
Permalink Reply by James R. Davis on -
In the language of the law, and what any jurist would understand ... Were it not for her speeding, there would not have been an accident.
Said differently, whether there was a double parked truck or not, this accident would not have occurred if the lady had not been speeding.
Speeding killed this rider, not a car driver who crept into an intersection, and not as a result of a double-parked truck, whether it was there or not.
All that had to be done in this case was to do that 'what if' analysis and as a result the jury could well come back with an apportioned negligence something like:
Trucking company = 10%
Motorcyclist = 90%
The payment awarded to the estate of the motorcyclist would almost certainly be ZERO dollars.
Who killed her? She did.
Copyright 1992 - 2010 by The Master Strategy Group, all rights reserved.
http://www.msgroup.org
(James R. Davis is a recognized expert witness in the fields of Motorcycle Safety/Dynamics.)
-
Permalink Reply by Andrew Kass on -
A very interesting and fascinating analysis of this accident. Have you been qualified as an expert in accident reconstruction?
-
Permalink Reply by James R. Davis on
-
I am not an accident reconstructionist. I work closely with them evry time I serve as an expert witness (motorcycle safety and Dynamics) though I use the same materials, formulas, and methods they do.
-
Permalink Reply by Joel Moses on
-
Fascinating. Please post more of this type of thing. I really enjoyed it and it is a very unique prospective for the members.
James R. Davis said:In the language of the law, and what any jurist would understand ... Were it not for her speeding, there would not have been an accident.
Said differently, whether there was a double parked truck or not, this accident would not have occurred if the lady had not been speeding.
Speeding killed this rider, not a car driver who crept into an intersection, and not as a result of a double-parked truck, whether it was there or not.
All that had to be done in this case was to do that 'what if' analysis and as a result the jury could well come back with an apportioned negligence something like:
Trucking company = 10%
Motorcyclist = 90%
The payment awarded to the estate of the motorcyclist would almost certainly be ZERO dollars.
Who killed her? She did.
Copyright 1992 - 2010 by The Master Strategy Group, all rights reserved.
http://www.msgroup.org
(James R. Davis is a recognized expert witness in the fields of Motorcycle Safety/Dynamics.)
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