Nissan Motor Co., General Motors Co. and other makers of electric and hybrid vehicles will be required by U.S. safety regulators to install warning systems that will automatically sound alerts to pedestrians.

The U.S. National Highway Traffic Safety Administration and advocates for the blind have raised concerns for several years about safety risks to pedestrians posed by hybrid and electric vehicles that make little engine noise.

"Even as we make giant leaps forward with hybrid and electric vehicles, we must remain laser-focused on safety," NHTSA Administrator David Strickland said in a statement Thursday announcing the start of a rule-making process. "With more and more quiet vehicles on the road, we have to consider their effect on pedestrians."