If our very own bike system is to succeed then we must solve the problem of headgear. The law mandates helmets for children under the age of 13 and for all working cyclists. If the most vulnerable and the most professional must ride protected, shouldn't we all?

Helmets are far too bulky to carry all the time and therefore bikes can't be spontaneously (or usefully) employed. Headed to a meeting and can't find a cab?...a bike share would be perfect, but not without a helmet. Fancy a ride after a dinner out?...again, only if we have our helmets at the ready.

A collapsible helmet is fast becoming an urban necessity, but the only existing models simply turn a large helmet into a slightly smaller one. We want a helmet no bigger than, and much, much lighter than a laptop; nearly flat, 9"x12" at most, and easy (very easy) to activate.

The traditional top hat gives the first clue, and the Reichstag dome suggests a formal solution: a pop-up spiral that locks rigid with an inflatable interior cushion. The pouch can become the cool cover and voila, safe riding!

See the 100 Ideas entry here and more on the prospect of collapsible helmets here.