Summary Offences Act 1981, ss 4(1)(a), 22

You can march on the road if your protest is large enough – sometimes police will even provide an escort to stop the traffic and make your march safer.

Stopping and sitting to prevent traffic can interfere with the general public’s right to use the road and could amount to the offence of obstructing a public way (a road or footpath) or of disorderly behaviour.