I have never thought an open face helmet as a safety item but more of a fashion statement.
But I never was into fashion anyway, so what do I know.
beeman
Definately not IMHO.
Picture the scene, Mr. "safe cos they race it" with his full spec Shoei, race leathers and and ultra loud exhaust pulls up at the side of me at a junction on the old A-64. I'm wearing an open face FM, 10 year old Gerieke jacket and jeans. I think "what a ****er, wait your turn", just as the *** pulls out on the fire engine coming from our right (The pump has had 5 miles to wind it up to about 75 and isn't going to stop this week). He see's it at the last minute, gives the 4 cylinder Yam full throttle, makes it across the road (right where turning taffic would be) just before he gets DENNIS imprinted on his head and falls off onto the verge. The Brigade don't even see him (or saw him hit the central reservation grass at 35 mph, slide to a halt and forget to put his feet down as the bike low sides).
Having stopped to pick the moron up I actually find the slot in the helmet is so narrow he struggles to look in his own mirrors, he can't hear a two-tone at a hundred yards and he's got a splitting head ache from the lid pushing on his temples. He is of course late for work and thinks riding like a *** in all his gear is the way to sort it out (so not all kits fault). This muppet of course is unlikely to be a repeat customer for the helmet manufacturer (nothing his fault of course).
He might be better off on a race track and he would have been better off if Fireman Sam had actually mashed him into the road face first, but isn't prevention better than cure?
For me, number one priority with a lid is wide vision, comfort and quietness. Open types are great at lower speeds on the first two. Flip fronts work very well (i've a Schuberth and a Roof Boxer), but that old FM is the best city helmet I've every used. It has a visor so sliding on your face isn't as black and white as people make out. The worst helmet I ever tried was also a flip front (BMW), but full face jobs seem to vary massively. I had a cheap JEBS full face that was fine, I tried an FM that was like sitting in a tank vision wise. I really don't think you can say full face good, open face bad until you try each product.
Goggles by the way are the best way to deal with fog. I wish I could have seen the faces of all the sports bikes riders I've passed in bad weather, but their untreated, badly ventilated visors prevent it ;-))
Ride safe & try before you buy.
Andy