Motorists who undertake on motorways could be hit with a £100 fine and three penalty points, despite the practice being widespread across the UK.
Undertaking is not in itself illegal, but carrying it out recklessly could result in penalties for either careless driving or driving without due care and attention. Some police forces may offer a driver education course as an alternative penalty.
What the Highway Code says
Rule 268 of The Highway Code states: "In congested conditions, where adjacent lanes of traffic are moving at similar speeds, traffic in left-hand lanes may sometimes be moving faster than traffic to the right. In these conditions you may keep up with the traffic in your lane even if this means passing traffic in the lane to you right. Do not weave in and out of lanes to overtake."
Although there is no specific law banning undertaking outright, it could easily be deemed a dangerous manoeuvre, which would render it illegal. Should a vehicle be travelling in the middle lane while the left-hand lane is clear, the driver could be issued a fixed penalty notice by police, and depending on the circumstances, any driver undertaking that vehicle on the left could also face punishment.
Why undertaking is frowned upon
Undertaking is the practice of overtaking another vehicle on its inside lane. This involves passing a slower-moving vehicle using a lane positioned nearer to the kerb than the one being overtaken. In the UK, this would normally mean a lane to the right of the vehicle you're passing.
It typically happens on multi-lane roads where traffic travels in the same direction, particularly on motorways. During heavy traffic conditions where all vehicles are travelling at comparable speeds, undertaking may be permissible to keep up with the flow in your lane, even if this means passing vehicles in the lane to your right.
That said, weaving between lanes to gain ground is not recommended. The Highway Code strongly warns against overtaking in general, and you could land yourself in serious trouble if you opt to cut across three lanes.
