[11] These assumptions and variables include whether the rear or front brake was applied first, how far the motorcycle travelled once it started sliding, whether a mark on the roadway was consistent with the motorcycle in question braking and whether it was upright at the time, the braking time before a mark was made, variations to data caused by the size and configuration of the motorcycle and the sliding surface, the range of possible decelerations, the slope of the surface covered, the condition of the rear brakes, how effective the rear brakes were at the time, whether the brake fluid was dirty and if so, how dirty and whether the hydraulic lines contained any air, the level of road/tyre grip available, the rate of deceleration, the comparative effectiveness of the front and rear brakes, the weight of the rider and passenger, the balance of that weight between the front and the rear tyre of the motorcycle, whether and when wheel lock occurred, where the pillion passenger was after he was thrown from the motorcycle, whether the pillion passenger hit any obstacles which affected the distance travelled after being thrown from the motor cycle, and the length of time between when the rear brake was applied and the front brake was applied, as well as errors introduced by scanning a Council plan of the intersection and scaling this from measurements taken from the site and by superimposing police photographs. Mr King did not examine the tyres of the motorcycle nor the road surface at a time proximate to the accident. It is not possible in these circumstances to give a reliable estimate, through reconstruction, of the speed of the motorcycle before it started sliding on its side.