Contravention 31 says "do not enter the box unless your exit is clear or if you are turning right and need to wait because of oncoming moving traffic.

It does not say anything about turning left. One can not see a clear exit as it is around the corner, especially where there is a pedestrian traffic light that goes green immediately after the green light for the traffic turning left.

Why isn't it treated like the right turn? Or is it?

If you stopped in it, then you contravene it due to the first part. Right turn doesnt have bearing hence the word OR.

There are two general caveats to it. DOnt enter at all until exit is clear, and dont turn right if you need to wait

Thank you for your response.

As for the left turn, the point is if the exit is clear as one can see before entering the box, what happens if , as they are turning left, the pedestrian light went green and the car in front stopped? Is it enough to show the exit was clear when entering the box and the pedestrians were not crossing?

They dont just go green. The system goes through a set routine to change. You see this well in advance.

The only time you'll be forgiven for stopping on a junction box going straight or left is if you had clear exit and as you enter the box, suddenly something or someone jumps in front of your car forcing you to stop to avoid an accident.

A friend got out of a ticket because he had clear exit, proceeded to enter the box and a drunken stepped in the road and fell.

My friend was forced to stop to avoid running him over and wait until the drunk got up.

The key point is the clear exit.

The highway code mentions going straight or turning right. It does not mention turning left. Perhaps because turning left by common sense does not block any traffic. Imagine one turning left and found the traffic on his left ahead jammed. How could he see it around the corner? Imagine while this car is stopping, another car coming from the opposite side and turning right stopped by the side of the car turning left, both in the box. The car turning right is excused and the one turning left is not?

I think there's logic why the highway code did not mention the car turning left.

The highway code mentions going straight or turning right. It does not mention turning left. Perhaps because turning left by common sense does not block any traffic. Imagine one turning left and found the traffic on his left ahead jammed. How could he see it around the corner? Imagine while this car is stopping, another car coming from the opposite side and turning right stopped by the side of the car turning left, both in the box. The car turning right is excused and the one turning left is not?

I think there's logic why the highway code did not mention the car turning left.

The Highway Code says you must not enter a box Junction if your exit isn’t clear.

Rule 174 says nothing about going straight on.

https://www.gov.uk/guidance/the-highway-code/using-the-road-159-to-203

The actual contravention that gets prosecuted is stopping on a box Junction, and the statutory defence is “if you are turning right and the ONLY thing preventing that is oncoming traffic (or other vehicles turning right)”. Again, nothing about going straight on.

Anyhow, if your exit isn’t clear (or there are vehicles that might turn left and block your exit), wait ..... go once you know your exit is clear and you won’t have to stop on the junction while turning left. Simples.