"It is estimated (e.g. by the NTSB) that fatigue contributes to 20-30% of transport accidents (i.e. air, sea, road, rail). Since, in commercial aviation operations, about 70% of fatal accidents are related to human error, it can be assumed that the risk of the fatigue of the operating crew contributes about 15-20% to the overall accident rate. The same view of fatigue as a major risk factor is shared by leading scientists in the area, as documented in several consensus statements."[20]