Remember kids... always wear a helmet. (The almighty bikeradar helmet thread)

In this case it appears under 14s will be covering up or getting a fine.

There's a press release from the other helmet charity Headway, which mentions the evidence used in the decision and adds

a compulsory helmet law in Jersey is unlikely to have a major impact on cycling activity in Jersey.

I suppose an already small number being reduced is still a small number, so no change there.