A rule in the Highway Code rule means all drivers in the UK can be fined £100 while driving on the motorway.
Many motorists can feel frustrated when the fast lane is being hogged by a slower driver.
As a result, people consider undertaking the other motorist - but few realise you can be given a hefty fine for doing so.
READ MORE: Christine McGuinness flooded with praise for not touching her kids' toys
The Highway Code states people shouldn't undertake other motorists for being slow on the motorway.
Even though there is no law about it, undertaking recklessly could mean that you receive a fine for careless driving or driving without due care and attention. This usually means three points on your driving licence and a £100 fine, although some police forces may offer a driver education course as an alternative.
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."
While there is no specific law prohibiting undertaking, it could easily be a dangerous manoeuvre - which would be illegal. If the vehicle is travelling in the middle lane when the lane to its left is clear, the driver could be given a fixed penalty by police and depending on the circumstances, any driver undertaking that vehicle on the left could also face a penalty.
What is undertaking and why is is frowned upon?
Undertaking is when you overtake on the inside lane. When you overtake a slower vehicle on the road using a lane that is kerb side to the vehicle you are passing. In the UK this would be a lane to the right of the vehicle being passed, says Birmingham Live.
This happens usually on roads where there is more than one lane in the same direction, such as motorways. Where traffic is congested and everyone is moving at similar speeds you may be able to undertake to keep up with traffic in your lane even though it means you pass vehicles in the lane to your right.
However, you shouldn't weave in and out of the lanes to get ahead. The Code strongly advises that you avoid overtaking generally and you can get into trouble if you decide to move across three lanes.
