Undertaking ought to be banned, with the undertaker being automatically at fault - just like anyone rear-ending vehicles in front
AIUI▸ where there are two lanes of traffic moving at different speeds this is not undertaking.
Correct, but be sure of the definition of 'lane' in this context. A marked, proper cycle lane, yes - a cycle or cycles in the same lane as vehicles doth not create a second lane.
The difficulty then is that where there is a cycle lane (I know there wasn't a cycle at the point in question) the cyclist is perfectly entitled to move faster than the standing traffic in the next lane.
Assuming you meant *cycle lane* there, I agree with you - but there wasn't.
From the
highway code Overtaking on the nearside (left) is legally acceptable if you are driving on a multi-lane carriageway in congested conditions, and the lane to the left is moving at a faster speed than lanes to the right. In these circumstances overtaking on the left is permissible although extra caution is needed for an awareness of other vehicles moving to the faster lane on the left.
This clearly refers to vehicle driving, not cycle riding.
So was this undertaking or traffic moving at different speeds in two lanes of traffic?
The street in question was no dual carriageway or even two lanes....you can check the road in question on google streetmaps. This was an extremely good example of why cyclists should *never* cycle on the kerbside of the road, unless going at or under the speed of the accompanying vehicles. Hold your place by cycling behind the vehicle in front, and overtake if necessary in the recognised manner, taking care that no vehicle is slowing to turn right. This is the rule for all traffic on our roads.
How much care is possible to avoid someone suddenly opening a door in front of you?
Like all traffic, only travel at a speed that you feel able to stop at if you need to. Example: if in a vehicle, and you rear-end the one in front, it can only be your fault. If on a cycle & you rear-end someone, same result.
The highway code is clear. Don't undertake on single carriageways. They may turn left, they may stop (or be stopped already - which I suspect in this case, and the cyclist wasn't being observant of the traffic around him), and if stopped, a door may open.