One lane crossover at contraflow road works

This sign means: One lane crossover at contraflow road works. It is a road works sign: slow down, follow the signs and keep to any temporary speed limit (Highway Code rule 288).

Official Highway Code caption: “One lane crossover at contraflow road works.”

Listed under “Road works signs” in The Highway Code: traffic signs (GOV.UK). For every sign in more detail, see the Department for Transport’s Know your traffic signs.