Powered by a couple of CR2032 watch batteries, the Vision Switch's three LEDs don’t light the road that much, but it's as a head-mounted backup light that it comes into its own.
At junctions, if the light’s mounted on your head, it provides a welcome illuminated nod to car drivers and the side windows provide some peripheral lighting.
Its other great use is for when things go wrong. In the event of your main light packing up – or if you have a puncture or mechanical problem – having a light on your head is a real boon. It’s great value too.