All helmets sold in the U.S. have to meet a CPSC (or is that CSPC) standard. It is the most stringent in the world, and there is little upside to trying to exceed it, so afaik no manufacturers do so. So "safest helmet" is a non sequitor. All helmets available for sale in the US are equally safe. The only helmet I've ever owned is now just over 10 years old. It was $35. An overstock Giro from a year or two before. I have a 61cm circumference head and XL Giro's fit that, many don't. That's what shopping around gets you. Details of fit, liner comfort, visor/no visor, colors ... Helmet design falls in two main camps: hockey or skate style with a more or less solid shell and several round vent holes and what I call 'hairnet style' with lots of angular venting. The skate styles seem to be popular with commuters and recreational cyclists and the hairnet style with road racer types. Helmet adoption in the US is pretty good. Despite that serious injury and death incidents are increasing year over year. In the 10 years I have owned my helmet, and more importantly, in the 35 years that preceded them, I never have experienced an accident where a helmet was consequential to the outcome. Chances are GOOD that if you get into real trouble out there that no helmet made will save you. Recently my wife left her 10 year old helmet in the locker at her gym which discarded it. She bought a Giro Register on Amazon in Neon Green/Yellow. I absolutely recommend anyone serious about helmet safety buy this helmet, in this color, and then do everything in their power (and they have a lot) NOT to ever need it.
What are you waiting for?