Yellow box junctions are designed to keep traffic moving, but drivers who stop inside one unlawfully can face a fine of up to £130. Barrister Daniel ShenSmith, a barrister of England and Wales and the creator of BlackBeltBarrister, has outlined circumstances in which motorists may have grounds to challenge a penalty.

The rules governing yellow box junctions are set out in Rule 174 of the Highway Code, which states that drivers must not enter a box junction until their exit road or lane is clear. There is, however, an important exception for motorists waiting to turn right.

Speaking on his BlackBeltBarrister YouTube channel, ShenSmith said: "174 of the Highway Code provides that you may enter the box junction and wait to turn right if you're stopped from doing so by oncoming traffic or by other vehicles that are also waiting to turn right."

At signalled roundabouts, motorists must not enter the box unless they can cross it completely without stopping. Rule 174 is backed by law under the Traffic Signs Regulations and General Directions. "And when there's law that underpins it, there's usually a fine that comes along with it," he said.

The amount of the penalty depends on where the offence occurs and the enforcement regime in place. Drivers who enter a box when their exit is not clear and then stop could face a £70 penalty in most parts of the country, while the charge can rise to £130 in London.

The rules are intended to prevent gridlock. If a driver stops inside a junction because traffic ahead is stationary, they can block vehicles travelling in another direction when the lights change.

ShenSmith said there are three circumstances in which motorists may have grounds to appeal a penalty. One example could be where temporary roadworks make it genuinely difficult for a driver to see whether the exit lane is clear.

He suggested that motorists could check whether temporary road restrictions were properly authorised by submitting a Freedom of Information request to the local authority. There could also be "narrower circumstances" where it is unreasonable to expect a driver to see the exit, such as a particularly large distance across the junction or where the road curves over a hill.

"If you've got a situation where you can't really see the other side and you can't reasonably see whether the exit lane is clear," he said, the driver may have grounds for a challenge.

Evidence, ShenSmith stressed, is crucial. "As with all of these things, evidence is the key," he said. He recommended taking photographs showing the junction from the position the vehicle was in before entering, and advised that dashcam footage could be particularly useful. "If you have, download it, save it," he said.

"Ultimately, if you want to challenge these things, there are lots of successful challenges by way of appeal," he added.