13 – Understanding the Behaviour of the Tigra through its Interaction with Rigby – According to A. Bailey

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The anatomy of a car striking a pedestrian in basically one of two things: a throw, or a running over. [source: Break a leg: Analyzing vehicle-pedestrian collisions  by John C. Gardiner, PhD, PE et al; Advocate Journal of the Consumer Attorneys Association of Los Angeles (CAALA), November 2011 [1]]. If the centre of gravity of the object hit is higher than the point of impact, then there will be a throw; if it is lower, then the victim goes under the vehicle. By the accounts, and as we should expect given his height in comparison with the Tigra, Lee Rigby was thrown. The anatomy of the throw depends on what the vehicle does during the impact, but the initial phases are the same whatever.

Fig.  57 – the phases of a throw with braking from the car after initial impact: from Break a leg: Analyzing vehicle-pedestrian collisions.

Fig. 57 – the phases of a throw with braking from the car after initial impact: from Break a leg: Analyzing vehicle-pedestrian collisions.

When the pedestrian is hit, generally speaking, his legs bear the brunt of the impact and are flung into the air and the body cartwheels so that it tends to arrive horizontally on or over the bonnet. What happens then is dependent on the behaviour of the car, but generally, at this stage the car may sustain damage to the bonnet and to the windscreen from sudden hard contact with the upper body and/or the head. The body has a tendency to flip because of the upwards movement of the legs, but depending on the behaviour of the car, this may become checked with contact. Even though the interaction might give the impression to an observer that the body is going backwards at this point, this is not the case. Instead, having been propelled forwards by the initial impact, this is the direction in which the body continues to move. The body initially sets off at virtually the same speed as the car was travelling when impact occurred. The important thing to remember is that the body has been launched – just as if someone had thrown a ball – and if left alone will travel through its own forward trajectory. Also important to note that the pedestrian is already pretty much at the top of his trajectory instantaneously after the impact, meaning left to its own devices, the body falls towards the ground. The power of the launch, and the potential distance to be travelled, is down to the force of the first impact.

Fig.  58 – from Break a leg: Analyzing vehicle-pedestrian collisions; stages in a collision at 25mph. Notice the catastrophic battering of the legs.

Fig. 58 – from Break a leg: Analyzing vehicle-pedestrian collisions; stages in a collision at 25mph. Notice the catastrophic battering of the legs.

If the car is braking on impact, the body will move in its flight relatively stationary to the car, or quite possibly get well ahead. It very much depends on how much the car is slowing. The body is always slowing, but the car, with its mechanical assistance, can slow much more quickly.

If the car maintains its velocity, or is accelerating into the impact, then the car will not be slowing as the body is, and will catch up. The body will travel in a relatively backwards direction and will meet bonnet and windscreen.  Being an obstruction to the parts of the car that are above the bonnet, the body will get struck again, and will get sent upwards for the car to pass underneath; the body is flipped over the car. The body, in this case, is still moving forward, but will land at the rear of the vehicle.

After the body hits the ground from a forward throw, it will bounce and then slide for a further small distance – if the area allows for it – until it comes to an eventual halt. In a typical event, the car driver is usually applying the brakes before, or slightly after the hit, so in most accidents we would expect to see the pedestrian being thrown forward clear ahead of the vehicle.

Lee Rigby, of course, was described as being carried on the bonnet by Amanda Bailey – and of course being flung a short distance. This would suggest to us that all the energy had gone from his flight during the course of the Tigra’s remaining travel and he had effectively landed on the bonnet. In other words, the car was travelling at the same rate of deceleration as Rigby, and he basically did his landing, bouncing and sliding on the bonnet of the car. His forward motion was dampened by contact with the bonnet, and the speed of the Tigra was such that he was able to rest on it thereafter. That the Tigra wasn’t travelling very fast is also evidenced by Rigby’s dismount. If you are being carried then when the object that is carrying you comes to a sudden halt and you are not strapped on, then you will continue at the same speed. Indeed, we are faced with the possibility that Rigby might have travelled further but was stopped in his progress by the wall. In Chapter Ten it was decided that Rigby landed with his feet up the road – this would fit with the scenario posited here.

Fig. 59 – the relative paths of Rigby and the Tigra.

Fig. 59 – the relative paths of Rigby and the Tigra.

To refine this further, maybe it was the case that the trajectory of Lee Rigby as he was flying through the air was such that it roughly coincided with the pathway of the Tigra. Perhaps he never became planted on the bonnet of the car so that he would dismount in front in the same direction as the car’s last vector path, but only appeared to be; in other words, Lee Rigby was hit hard enough to launch him into the air as expected, and as he descended through the air, his body slid on the bonnet in such a way that he kept his original trajectory. At the same time, the momentum was inevitably also taken out of his flight, but not enough to turn his effective flight into a carry. The scenario only created an impression of him being carried in a given direction, when in fact he was being assisted on the path of an original trajectory. In other words, when there was contact with the bonnet, there was not enough friction to stop Rigby following his initial direction. This meant that even though the Tigra turned out from beneath him, Rigby still flew in his original direction of travel which would take him to the right of the Tigra in its final position. The diagram in Fig. 59 explains in graphical terms, which might be a bit more helpful than this long-winded paragraph.

In the end, regarding this matter, there are just issues here that cannot yet be resolved. What we can safely say is that the Tigra was decelerating as it hit Rigby, or instantaneously afterwards, and was most probably decelerating all the way to the road sign stanchion.

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[1] http://www.meaforensic.com/vehicle-pedestrian-collisions-accident-reconstruction-expert-witness-