Under the Highway Code it is acceptable to undertake on a motorbike
Passing a vehicle on the left (usually referred to as undertaking) is acceptable if the vehicle is signalling to turn right and there is enough room to do so or where you are in a separate lane and the other vehicle is being held up by traffic ahead.
Any manoeuvre should be done with care. Where you were undertaking you may find you are being prosecuted on a charge of Driving Without Due Care and Attention (Careless Driving) or, if you were also weaving in and out of traffic or traveling at excessive speed, Dangerous Driving. If you were involved in an accident at the time there is no requirement for a Notice of Intended Prosecution to be served on you.
We often come across arguments that no compensation should be payable in undertaking situations. The reality is that any case will turn on its specific facts and the liability issues may well be the same as for filtering. However, the existence of any conviction for either careless or dangerous driving on your part, will go a long way to reducing any responsbility the other side may have to take, so it is always worthwhile obtaining legal advice.
Highway Code Undertaking & Filtering
Rule 162
Before overtaking you should make sure
- the road is sufficiently clear ahead
- road users are not beginning to overtake you
- there is a suitable gap in front of the road user you plan to overtake.
Rule 163
Overtake only when it is safe and legal to do so. You should
- not get too close to the vehicle you intend to overtake
- use your mirrors, signal when it is safe to do so, take a quick sideways glance if necessary into the blind spot area and then start to move out
- not assume that you can simply follow a vehicle ahead which is overtaking; there may only be enough room for one vehicle
- move quickly past the vehicle you are overtaking, once you have started to overtake. Allow plenty of room. Move back to the left as soon as you can but do not cut in
- take extra care at night and in poor visibility when it is harder to judge speed and distance
- give way to oncoming vehicles before passing parked vehicles or other obstructions on your side of the road
- only overtake on the left if the vehicle in front is signalling to turn right, and there is room to do so
- stay in your lane if traffic is moving slowly in queues. If the queue on your right is moving more slowly than you are, you may pass on the left
- give motorcyclists, cyclists and horse riders at least as much room as you would when overtaking a car.
More Information
https://www.gov.uk/guidance/the-highway-code/using-the-road-159-to-203
