How had someone not thought of this before? Bike rental company Bike and Roll NYC today began renting sanitized helmets to Citi Bike users and clumsy pedestrians for $3 per day and $15 per week.

Bike and Roll NYC President Chris Wogas said helmets have always been included with the company's cycle rentals, but today marks the first time they'll be available a la carte. While the launch of Citi Bike was certainly a contributing factor in the decision to make helmets available, Wogas said anyone can rent them for whatever purpose, as long as customers are down to sign a waiver that lets the company track the helmets' whereabouts.

"We just saw a need in the marketplace," he said.

The helmets are sporty-looking Trek Bontragers, and will be thoroughly sanitized with Lysol and all-purpose cleaner after each use. They'll also be inspected for cracks by Bike and Roll staff, since Wogas said helmets don't last forever—like skulls, they weaken with impact, meaning even dropping them on the concrete can diminish their protective powers.

"We probably replace 80 percent of our helmets over a 12 month period," he said.

Some helmets will undoubtedly require more than a good scrub down before they're ready to return to the road. Wogas has plenty of bizarre tales of helmets being returned with mysterious foodstuffs—we hope—adhered to the inside.

"Somebody could have been eating an ice cream cone, if someone is drinking a soda, it can get spilled in the helmet," he said. "Some helmets have come back with such bad ice cream spills in the foam that we've had to throw them out," he said. [Editor's note: That probably wasn't ice cream.] "We're on the side of 'would we wear it?'"

Helmets will be available at ten locations around the city, including near Brooklyn Bridge Park, Central Park, Riverside Park, East River Park, Battery Park and Pier 84.