Congestion Lock

In any practical sense it is impossible for motorways (or most roads) to become gridlocked as is so often described in news reports. What they mean is 'congested'.

Gridlock is a feature of roads laid out in grids (the clue is in the word) and is made more likely by roads having alternate one-way systems - as in Manhattan. Cars line up around the block and cannot move forward or turn due to the car(s) in front - as illustrated below courtesy of Wikipedia.

In the right circumstances gridlock can be achieved with only four cars in a square (or grid). Generally speaking gridlock would be of minimal interest in news terms.

News is interested in the frustration and anger (etc) generated by people not getting where they want or need to be, as more people are involved and the pictures are better, and this is usually due to the amount of traffic not it's delicate configuration on a grid of streets. This is congestion but news prefers the word gridlock.

FFS!