The Highway Code changes that were implemented in July 2022 included changes for cyclists riding two abreast in certain circumstances. It is sadly obvious that many car drivers are not familiar with the code, but how many of us know when we should or should not ride two abreast? In case it helps, here’s a quick summary:
Rule 66 says: You should be considerate of the needs of other road users when riding in groups. You can ride two abreast and it can be safer to do so, particularly in larger groups or when accompanying children or less experienced riders. Be aware of drivers behind you and allow them to overtake (for example, by moving into single file or stopping) when you feel it is safe to let them do so.
This means that there is some judgement involved, which means being aware of other road users around you and being considerate is vital. Rule 163 specifies that overtaking vehicles should leave at least 1.5m when overtaking (more at higher speeds), so if the road is wide enough for a vehicle to pass with 1.5m space then riding two up is actually better as it means a shorter obstruction to pass.
As roads narrow it might be fine to continue to ride two abreast if there is still 1.5m plus the width of a vehicle space, so that can have a bearing on how close together you are. Once it gets narrower riders should ride in single file up to the point where there is no longer 1.5m plus the width of a vehicle left. At this point it means safe overtaking whilst riding is not possible, so riding two abreast in the centre of the road is acceptable, but in the knowledge that to allow a vehicle to pass in either direction will require pulling over.