This is an example of a collision between a motor cycle and a motor car – vehicles of widely differing mass.
A 999cc motorcycle collided with the rear of a stationary motorcar. The rider of the motorcycle, who was not injured, admitted that he collided with the rear of the car but stated that it was at a low speed. The motorcycle fell on its side after the collision. Two occupants in the car claimed injury as a result of the collision.
A thorough inspection of the car failed to discover any damage or marks that could be attributed to the collision although it was accepted that the rear bumper could have been replaced prior to the examination. A thorough inspection of the motorcycle revealed scratching to various parts consistent with the motorcycle falling over. Also, there was a flat-spot on the front tyre that was consistent with skidding under heavy braking described by the rider just before the impact.
The mass of the motorcycle and its rider was approximately 274 kg. The kerbside mass of the car was approximately 1580 kg. The car has nearly six times the mass of the motorcycle.
The collision force experienced by the car would have been equal in magnitude but opposite in direction to the collision force experienced by the motorcycle. This is in agreement with Newton’s Third Law.
However, the effect of the collision forces in terms of the acceleration/deceleration and change in speed of each vehicle would have been inversely proportional to the mass of each vehicle. This means that the change in speed of the motorcycle as a result of the collision would have been about six times the change in speed of the car. This is in agreement with Newton’s Second Law.
The widely argued threshold for whiplash injury is a change in speed of 5 mph to the struck vehicle. To cause such a change in speed, the motorcycle would have to strike the rear of the car at about 30 mph. At this impact speed there would have been significant damage to the rear of the car and to the motorcycle. Also, it is highly likely that the rider of the motor cycle would have been injured at this impact speed.
The conclusions of this investigation were that the collision probably took place at no more than 5 mph and that it was highly unlikely that occupants in the car would have been injured as a result of the collision.
• The claims for personal injury were dismissed.
• The Claimants were ordered to pay 90% of the Defendant’s costs.
• The Defendant was ordered to pay for the cost of a new rear bumper for the Claimant’s vehicle.
In his summing up the Judge stated:
“The expert from GBB and his report impressed me. The report was thoughtful, carefully researched and the findings were based on careful investigation and clear photographs are evidence of that. All in all I find that his evidence is credible, believable, well thought out, well presented and acceptable to me.”
This is an example of a high-value claim involving a collision between a Leyland Tiger coach and a Toyota Celica. It shows how research and analysis can be instrumental in establishing the truth.
The Toyota was travelling in front of the coach when it braked suddenly as a pedestrian stepped out onto a
crossing. The coach was unable to stop and it struck the rear of the Toyota.
The coach was carrying passengers travelling to a wedding. A majority of the passengers claimed personal injury.
GBB was asked to comment upon the likely speed of impact and the effect of the collision upon the occupants of the coach
An examination of the tachograph chart showed that the coach was travelling at 18.6 mph (8.31 m/s) at
the moment of impact. A momentum calculation was then carried out to determine the final speed, the acceleration and the average collision force experienced by each vehicle.
The final speed of each vehicle was calculated as follows:
Mass ratio of the vehicles: Coefficient of restitution: r = 0.2
(This takes into account the balance between elastic and inelastic
Initial velocity of the coach: U1 = 18.6 mph (8.31m/s)
Final velocity of the coach: 16.8 mph or 7.51 m/s
Final velocity of the car: mph or 9.18 m/s
Change in speed of the coach: Δv = 8.31 – 7.51 = 0.8 m/s (Deceleration)
Change in speed of the car: Δv = 9.81 – 0 = 9.81 m/s
The average acceleration of each vehicle as a result of the
collision can be calculated from: a= where Δt is the collision time of around 0.2 sec.
Average acceleration of the coach = -0.8/0.2 = -4.0 m/s2 or 0.41g.
Average acceleration of the car = 9.18/0.2 = 45.9 m/s2 or 4.68g.
From this it can be seen that the magnitude of acceleration experienced by the car was much larger than that of the coach. This is due to the large difference in mass between the vehicles.
The average collision force can now be calculated from the equation resulting from Newton’s second law: F = ma
Average collision force acting on the coach = 14620 x -4.0 = -58,500 N
Average collision force acting on the car = 1275 x 45.9 = 58,500 N
This shows that the average force experienced by the car is equal in magnitude but opposite in direction to that experienced by the bus despite the large difference in the mass of each vehicle. This is in complete agreement with Newton’s 3rd Law.
Bus testing research carried out by GBB shows that the value of deceleration experienced by the coach is similar to that which would occur under emergency braking.
The graph below shows the deceleration of a bus under emergency braking along with the deceleration of a striking vehicle from one of the full-size crash carried out by GBB.
coach graph image
It can be seen that the deceleration experienced by the striking vehicle in Crash Test 2 (blue line) is much greater than that experienced by the bus (black line) during emergency braking.
From this it was inferred that since the occupant of the striking vehicle in Crash Test 2 was not injured, then it was considered to be highly unlikely that occupants in the coach involved in this collision would have been injured. Other evidence was also considered by the court which resulted in the following judgement.
Twenty claimants had their cases dismissed. Another four claimants persisted but were forced to drop their claims on the second day of the trial at Manchester County Court. The claimants were ordered to pay £25,000 costs and their file was passed to the Director of Public Prosecutions and Greater Manchester Police with a view to possible proceedings regarding fraud. Subsequently 4 of the individuals involved have been sentenced.
This is an example of a fraud involving a Rolls Royce, a rental truck and a ficticious motorcycle.
A Rolls Royce was alleged to have been parked at the side of a country lane when it was struck by a rental truck. The driver of the rental truck (the Defendant) alleged that a motorcycle approached him too quickly and out of control whilst emerging from a left-hand bend. As a consequence, the truck driver swerved to his right and collided with the nearside of the Rolls Royce. According to an assessor, the Rolls Royce had a pre-accident value of £32,000.
GBB was instructed to examine the Rolls Royce together with photographs of the rental truck and establish:
• The pre-accident condition of the Rolls Royce.
• The likelihood of the collision occurring as alleged.
• The likelihood of the collision occurring at all.
A thorough investigation by GBB established the following facts:
1. With the use of eddy current sensors, large areas of filler were detected beneath the painted surface of the Rolls Royce. Filler was also visible on the damaged surfaces. The Rolls Royce had been ‘restored’ using copious amount of filler and its true value prior to the collision was nearer to £10,000.
2. An examination of the damage to both vehicles revealed that they had come into contact. However, the damage was not consistent with a single impact. There had been contact between the two vehicles, but the rental truck had struck the Rolls Royce twice and the two contacts could not have both been accidental.
3. The involvement of a motor cycle was fanciful. The expert in the case had been a police motorcyclist and the description given by the Defendant could not have occurred despite the owner of the Rolls Royce (the Claimant) saying they ‘had seen a motorcycle’.
On the basis of the evidence uncovered by GBB, it appeared that the Claimant had realised that she had bought a ‘pup’ and in an attempt to recover some of her money she had arranged for the Rolls Royce to be struck by the truck to damage it beyond repair. The rental truck had struck the Rolls Royce twice because the damage from the first impact was not great enough to have the vehicle written-off.
It was expected that the insurance company would pay the Claimant according to the assessor’s valuation of the Rolls Royce. An out-of-control motorcycle was simply an invention to provide a cause for the collision between the rental truck and the Rolls Royce.
The claim was brought before Liverpool County Court and finally heard in February 2007. The claim was dismissed.
The timescale of the accelerometer was adjusted so that the impact started at 0 seconds. The acceleration reached a peak of 0.3g at 0.32 seconds. The speed change displayed oscillations as the vehicle’s separated.
The wheels of the PCV were stationary and remained so throughout the collision phase.
The sprung mass was accelerated to 0.43mph.
The un-sprung mass did not move as the acceleration applied was insufficient to overcome the frictional force between the tyres and road surface.
Y Axis – Peak vertical accelerations of 0.29g and 0.47g were observed simultaneously at 0.15 second. This suggests an instantaneous compression disparity of 0.18g.
A trough of –0.28g of the head occurred at 0.36 second, where the chest acceleration is –0.09g; a disparity of 0.19g.
A trough of –0.48g of the chest occurred at 0.44 second. The head acceleration was –0.14g demonstrating a disparity of 0.34g.
The time delay of 0.08 second may suggest an elongation of the neck structure.
Z Axis – The first head acceleration peak was found at 0.62g; the chest acceleration at that point being 0.1g. This occurred at 0.1 second and demonstrates a disparity of 0.52g.
At 0.14 second the peak head acceleration was –0.5g with the chest at –0.03g. The disparity is 0.47g.
By 0.52 second, the peak chest acceleration was –0.39g with the head at –0.21g. This is a disparity in favour of the chest of 0.18g.
The timescale of the accelerometer was adjusted so that the collision started at 0 seconds. The start of the collision was defined to be when the acceleration became negative and stayed negative. Peak deceleration of 2.4g occurred at 0.19 seconds. The initial deceleration phase took 0.4 seconds, rebound then occurred.
From integration of the acceleration pulse, it was calculated that the impact speed was 8.0 ± 0.1 mph, and that the delta v (∆v) was 9.7 ± 0.1 mph.
The occupant acceleration is expressed in two components; “Y” which denotes the vertical axis, and “Z” which denotes the longitudinal.
Y Axis – Peak vertical (Y) chest and head acceleration of 3.68g and 5.91g occurred at 0.2 and 0.26 second respectively.
At 0.26 second, the chest acceleration was 1.21g allowing for a maximum disparity of 4.7g.
Z Axis – A peak g of 1.9g occurred at the chest at 0.15 second. At this point, a head acceleration of 0.7g was experienced. (Peak 0.8g occurring at 0.17 second.). This first maximum disparity of 1.2g occurred.
A peak head acceleration of –3.06g occurred at 0.24 second. At this point the chest acceleration was 0.3g. The disparity was 3.36g.
A peak forward chest acceleration of 3.2g occurred at 0.27 second. The chest acceleration was 0.6g.
At 0.41 second, the head acceleration was –1.4g the chest being 0.2g. The disparity was 1.6g.
A second forward peak acceleration of 2.9g occurred at 0.57 second. The chest acceleration was –0.4g. The disparity was 3.3g.
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