Posted By Haroon Rasheed Tabani Dear All Recently I participated in a workshop on risk assessment. During the quantification of SEVERITY and LIKELIHOOD, there was a big discussion about their concepts. One group of participants were of the opinion that SEVERITY never changes whatever be the control measures be taken only LIKELIHOOD changes. The another group did not agree. They argued that if somebody works at height using a safety belt or harnesses, the severity of the injury will be decreased.Could any one help me to clear the concept of these two important terms. Thanks

Posted By John Webster This very much depends upon the risk you are trying to control. For example, there is much focus at the moment on railway accidents. Installing equipment to prevent drivers overrunning signals at danger (SPAD incidents) will significantly reduce the LIKELIHOOD of a collision, but should, despite the control measures, a collision occur it will do nothing to reduce its SEVERITY. However, re-designing carriages so that they better absorb impact damage, are more likely to stay upright and are less likely to catch fire etc. will not reduce the LIKELIHOOD of an accident occurring, but will reduce its SEVERITY. Naturally, a combination of control measures which tackle both likelihood and severity is what we should be aiming for. Hope this helps. John