An FBI analysis of police officer deaths is revealing a troubling and persistent pattern in which substantial numbers of officers were not wearing body armor or seat belts when they were fatally shot or involved in deadly vehicle accidents.

Of the 46 officers killed by firearms in 2014, 11 were not wearing bullet-resistant vests. During the same period, 10 of 28 officers killed in vehicle accidents were not wearing seat belts. Six of the 10 auto accident victims, according to the FBI report, were ejected from their vehicles during the crashes.

Although traffic-related incidents have consistently been among the leading causes of officer deaths, law enforcement seat-belt compliance has hovered around 50%. The compliance rate among the general public has been estimated at 86%, according to the National Highway Traffic Safety Administration.

In fatal shootings, meanwhile, 36% of officers killed from 2003 to 2012 were not wearing body armor, according to FBI statistics.

A rising number of agencies have adopted mandatory-wear requirements in recent years. Those rules have been met with resistance from some officers who say that the armor is often too uncomfortable, especially in warm climates, and that seat belts slow their movement in and out of patrol cars, USA Today reports.