Undertaking / filtering on left?

vehicles are allowed to undertake in lanes of slow moving traffic, i.e. at junctions and roundabouts..

what the law permits (eg undertaking, cycle lanes on the left) and what is actually advisable/safe are two very different things

filtering up to lights on the left hand side when traffic may be turning left (eg lights are red but you dont know when they are likely to turn green is inherently risky. this is much worse with trucks and long vehicles because there is actually a blindspot so they could be looking around quite diligently yet still miss you if you are approaching in their blindspot when they look at their left mirror.

generally if i know the lights and they have just turned red i will consider filtering on the left (also taking into account of the types of vehicles that I will be undertaking), but if i have not observed the sequence of lights i tend to filter on the right hand side because of the increased visibility

if you appreciate the levels of risk when entering a situation you will have better information with which to make a risk assessment