Requiring the use of gritted paint for road markings could help ensure the rider doesn't slide on them. Applying grit to all manhole covers could help make them safe for motorbikes to ride over without the chance of slipping
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I have recently started riding a motorbike, and trying to navigate around road markings, manhole covers as well as potholes makes riding more dangerous than it needs to be.
We are already at more risk from harm, we do not need the risks made higher by something that can be avoided.