"Our findings indicate that the 1994 Rule was followed
by a reduction of almost half in the crash rate. On the other hand,
crashes that occurred as a result of low visibility-often because
of rain, fog, or clouds-increased from 5 percent to 32 percent of
all air tour helicopter crashes in the 14 years after the new
regulation."
Source: Senior Author Wren L. Haaland, a
2009 graduate of Johns Hopkins University who conducted a study as
an undergraduate research assistant with the Bloomberg School's
Center for Injury Research and Policy on the effect of FAA's SFAR
71.