This paper analyses the UK in-depth crash data collected under the Co-operative Crash Injury Study to identify the optimum crash conditions for an advanced frontal crash test procedure. The paper recommends that a revised frontal crash test should employ a crash test of at least 60 kph into a deformable block with at most a 40% overlap. This condition represents that of greatest risk of AIS 3+ injury. Fatalities are found to be rare at impact severities below 50 kph. Improving frontal protection by using a 50 kph crash test will only marginally decrease fatality numbers. Intrusion is found to be an important causal factor for injuries - in general the condition of high speed crashes with low intrusion results in fewer severe injuries than the condition of a low speed crash with high intrusion. Injuries are also more often severe when the frontal overlap is low. A crash with overlaps below 40% results in more AIS 3+ injuries than crashes with overlaps below 60% but with the same impact severities. The highest proportions of occupants with AIS 3+ injury is seen when the delta-V is above 60 kph and the overlap is below 40%. The highest median values of intrusion are also found when the impact severity is above 60 kph and the overlap is below 40%. There is however only a weak relationship between intrusion and delta-V.