You can Google for more information if you’re interested but there’s plenty of good evidence that bike helmets are either ineffective or an actual liability. I was particularly struck by a comment by a bicycle helmet test engineer who said that he had *never* seen a bike helmet worn properly outside his lab. And if you’re not wearing it properly it really is just an ugly hat.
Regarding your crack, it’s difficult to judge from the photo but:
“Helmets work by absorbing impact energy through the crushing of an expanded polystyrene liner. Once compressed the liner stays compressed. It does not bounce back to its original form like reusable helmets for some other activities. If a helmet splits before the liner has partially or fully compressed – and this is often the case – then it has simply failed. It will not have provided the designed protection and may in fact have absorbed very little energy at all.”
I know how to wear a bike helmet, thank you very much.
And yes, bike helmets (at least the ones that aren’t BMX-style helmets, not sure what’s true of those) are use-once. Once it’s been hit once (even just from dropping off handlebars) its compressiveness is gone and it’s time to replace it. Sounds fine to me — it’s like insurance where you pay a one-time fee and then you’re covered until you actually need to use it.
Yeah, I did the same thing a few years ago & cracked the helmet, the on-road tram tracks here in Melbourne are perfect for the front wheel to drop into & instantly stop, allowing a short period of flying… BTW, helmets are compulsory here since the 80′s, I think it dropped the rate of cycling by about 75%, only now starting to recover.