Increased awareness of road safety and a need for estimating vehicle speeds in accident reconstruction has spawned an ever increasing literature on speed estimation from vehicle damage. The theory used was quite simple and robust when first introduced in the early 1970s. The push of legislated fuel economy has produced a fleet of smaller and lighter cars which are structurally different from the vehicles of the early 1970s. The changing vehicle structure among other factors has reduced the robustness of the early analytical models introduced by Campbell (1972) and McHenry (1974). This paper goes back to a single variable, the slope of the impact speed/residual crush curve and derives a set of crush coefficients and their variance.