Bus and cycle signs
Route for use by pedal cycles only
What it means
A blue circle, so it's an instruction: this route is for pedal cycles. It marks cycle tracks running alongside the road or away from it altogether. You MUST NOT drive or park on it. Where it runs beside the road, expect cyclists moving at speed on your left and check for them before turning across.
Highway Code Rule 240 — read it on GOV.UK
Test yourself on signs like this one
Free with an account. Each answer tells you what the sign means, not just whether you were right.