Large intersections are marked with a large yellow box with diagonal squares. This is known as a box junction. This is to indicate

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The Role of Diagonal Yellow Lines in Major Junctions

In busy traffic environments, understanding the function and rules associated with a box junction is crucial. Let’s learn why major junctions have diagonal yellow lines and the significance they hold in traffic management.

Defining a Box Junction

A box junction is a feature designed to control road traffic and avoid gridlock at bustling junctions. It is characterized by a large yellow box marked with diagonal yellow lines, a common sight at large intersections and places witnessing heavy traffic flow.

The Purpose Behind Diagonal Yellow Lines

The principal reason major junctions have diagonal yellow lines is to keep the intersection clear, facilitating the swift passage of emergency vehicles and ensuring a smooth traffic flow. The rule is simple: drivers should enter the box junction only if they have a clear exit, a practice to adhere to even when the signal is green.

The Consequences of Not Following the Rule

Ignoring this rule can have serious repercussions. If a driver enters when the exit is not clear, it leads to congestion and blocked intersections, posing dangers to other drivers, pedestrians, and emergency vehicles.


To sum up, it is essential to abide by the rules governing box junctions to prevent chaos at intersections where major junctions have diagonal yellow lines. It promotes safety and order, encouraging drivers to only proceed when their exit is clear, even if it entails waiting for a short period at the entrance.