Johnson vs. Derby Cycle Co.
In the Johnson case, I assisted the attorney for the plaintiff, Green assisted the attorney for the defendant. Johnson, a high-school student working until midnight at a fast-food restaurant, decided to buy a bicycle for transporting himself to and from work. He did so, purchasing a product of Derby Cycle Co., and on the third night of cycling he had an accident. He was descending a hill of a four-lane arterial, on a bicycle equipped with the all-reflector system of nighttime protection that is required by federal regulation, but not using a headlamp. He passed through the green of a signalized intersection, which changed just about as he went through it. The driver of a jeep, ascending the hill and intending to turn left at the signal, saw the signal change and decided to turn at the preceding intersection. He turned left directly in front of Johnson. The jeep was fitted with a fiberglass superstructure. Johnson hit the right rear corner of this structure, tore out the corner post and the two adjacent windows, and continued through to fall onto the road surface, incurring severe physical and neurological injuries.
The plaintiff's case followed my suggestions. We did not dispute that Johnson, by not using a headlamp, was riding dangerously. In fact we insisted on that theory. We argued, however, that Johnson had been misled about the efficacy of the all-reflector system into believing that such equipment made it safe to ride at night. My testimony concerned four subjects, two scientific, the third historical, the fourth documentary. First, the danger of riding at night without a headlamp. Second, the inability of the all-reflector system to disclose a cyclist approaching several different potential collision situations, including the one in this accident. Third, the history of the all-reflector system, telling that it had been invented by the bicycle manufacturers, then, in 1972, adopted by the federal government for its bicycle regulation, then supported by the manufacturers at every opportunity, including the controversy about that regulation (I had sued the CPSC over the initial regulation, pointing out the undoubted fact that the all-reflector system could not perform the functions assigned to it), and the presentation by the manufacturers to the traffic-law experts (National Committee for Uniform Traffic Laws and Ordinances), saying that the nighttime headlamp requirement in traffic law was void because the federal requirement for the all-reflector system had pre-empted the field. Fourthly, that the legally-required safety manual that Derby was required (as are all manufacturers) to supply with its bicycle said that a headlamp should be used when cycling on trails, but ignoring roads, and that the officers of Derby had stated, under oath in answers to interrogatories, that they relied on the federal requirements as defining a safe bicycle and had no knowledge of any state laws that required cyclists to use headlamps when cycling at night (which all states have done for many decades). My testimony was supported by Johnson's testimony, and by that of the chairman of the psychology department at Rutgers University, who testified that 80% of the high-school students in that area believed that the all-reflector system made a bicycle safe to ride at night.
My testimony on these subjects was preceded by what was, in effect, a lecture to the jury on the proper methods for analyzing and reconstructing collisions, particularly those involving bicycles, so that the jury would be able to understand where Green's presentation was defective.
The defense chose to argue that Johnson was riding even more dangerously than plaintiff had argued (thus putting more blame on Johnson than merely failing to use a headlamp), that Johnson's front reflector had been plainly visible for the last 600 feet of his approach (that put the blame on the jeep's driver), and that some second, unknown motor vehicle had also hit Johnson. Green testified to all of these points, or tried to. Most of my time expended in this case went to analyzing these claims, as made in initial reports and deposition, trying to figure out Green's errors so that I could make some kind of sense about the claims. That is why I later testified to the proper methods of collision analysis and reconstruction, so the jury could understand his errors before he presented them. That is also why I initially testified to rebut the claims that were made in Green's report and deposition, by showing the proper results.
Defense claimed that Johnson was traveling at 41 mph at the point of impact. Green presented two kinds of evidence: the deformation of Johnson's front forks, the speed naturally developed on the descent. My analysis and evaluation of the evidence from fork deformation is contained in my review of the relevant chapter of Green's book. Evidence from Fork Deformation. As part of his analysis of this collision, Green based some calculations on what he said was the maximum possible speed of the jeep in making a left turn, 8 mph, based on some kind of vehicle analysis that I did not track down. I found a jeep of the same model in a used-car lot, and persuaded the salesman to drive it around right-hand turns (less traffic interference, probably shorter radius turn), and he comfortably made right-hand turns at 18 mph.
Green's second method used the standard formula for determining the energy available from a loss of altitude, E = MgH, where M = mass, g = acceleration of gravity, H = height lost. Green then assumed that the speed of the bicycle was developed by all of this energy, ignoring that which was lost in the various frictions: tires, bearings, air. He therefore overstated the speed achieved on any specified slope, as if the cyclist were falling in a vacuum. Since at 25 mph on the level, about 75% of the energy being used is consumed by air resistance, Green has made a very serious overestimate of speed achieved on any significant slope.
I testified to two accurate ways to determine speed on a slope. The first is plain experimentation. Ride the slope and see what speed develops. I did so, on a bicycle somewhat better than Johnson's. The speed at the point of impact was 33 mph. The second is calculation. If one knows the values for the various sources of power (in this case, gravity operating on known slopes) and the various resistances (stated in several books on the subject) it is possible, using the known laws of physics, to calculate the speed at any point of a descent. To get a result in any reasonable time requires a computer program, which I have developed. When that program was applied to Johnson's case, its result agreed pretty closely with my measured actual speed. When the resistances were set to zero and the results recalculated, the result agreed with Green's method of calculation that ignored all resistances.
Defense claimed that Johnson was riding close to the centerline of the road. Green supported this claim by two items: analysis of the angle of the jeep to Johnson's path, claiming that the angle of impact along the side of the jeep was so shallow that the jeep could not have turned much from straight up the road, and by the position of Johnson's body after the impact. The shallow-angle argument both conflicted with his claim regarding the deformation of the front forks and with the shape of Johnson's bicycle after the collision, and the position of Johnson's body after the collision was not a reliable indicator of the position of the impact, because the impulse vector of the collision was not calculable. All in all, the evidence was very dubious, and Johnson's position was irrelevant to the question of who, or what, was the cause of the collision.
Defense claimed that computer simulation showed that had Johnson been approaching at a different speed or closer to the curb, the collision would not have occurred. Green plotted his assumed position of the point of impact and the movements of the two parties according to his assumed velocities. He then reduced Johnson's simulated speed, showing that then the jeep passed in front of him. He then moved Johnson's path to near the curb, showing that then Johnson passed in front of the jeep. We know that a collision occurred, but we don't know, for sure, either the exact point of impact or the exact velocities of the parties. If it is assumed that Johnson was traveling, say, only 25 mph, then the proper adjustment would be to simulate his movement back from the point of impact, because we know that the impact did occur, at 25 mph instead of 41 mph. Green was merely arguing, in effect, that had Johnson worked overtime that evening, he would not have met Rivera's jeep, but Green has apparently no conception of this error, or of the irrelevance of his argument.
Defense claimed that Johnson's front reflector was visible for the last 600 feet of the approach. This is the item of evidence that the defense's attorney was trying to get me to testify to, as shown in Green's Comments about my testimony. Green had no substantive testimony to give about this subject, no tests that showed this. His argument was based on the legal requirement for motor-vehicle headlamps, under some conditions and in some directions, to make people visible at 600 feet.
Defense claimed that a second motor vehicle hit Johnson and dragged his body to a point 135 feet from the point of impact. This claim was not made either in Green's report or in his deposition, but Green makes it in his Comments about my testimony. The police report places Johnson's point of rest 95 feet from the farther side of the intersection where the collision occurred. Therefore, the total movement of Johnson's body from the point of impact must have been less than 95 feet. I deduce that Green's attack on my qualification to calculate trajectories of bodies involved in collisions is related to this claim. Green must have wanted to present some kind of testimony saying that Johnson's body must have fallen short, immediately after the known collision, of his final position, and been swept along by this second mystery vehicle.
Since my testimony was part of plaintiff's case, it was presented before any testimony by Green. To save the expense and delay of a return trip to New Jersey for rebuttal testimony, the first part of my testimony concerned the accepted scientific analysis of the situations discussed in those of Green's claims with which we were familiar from his reports and his deposition. That testimony was rather in the form of a lecture about the standard physics of these situations, involving vectors, momentum, energy, etc., and my criticism that Green's methods and hypotheses were not in accordance with the standard elementary physics that I had learned at UC Berkeley and which all engineers and physicists were supposed to learn. Then I proceeded to present my testimony about the accident situation, including the danger of riding without a headlamp, Johnson's speed as revealed by test and by calculation, the operating principle of reflectors and their limitations, and about the history of the all-reflector system. Green was present during much of this time; I don't know just how much, because I paid attention to the attorneys, the jury, and the judge. Once I was released, I returned to my home in California.
Green presented his testimony as part of the defense case, but what it was I do not know. In any case, the jury found for the plaintiff, and, I understand, were of the opinion that Green had presented junk science.
Derby Case page last changed: 25-Sep-08