What does a marking indicating 'except when forced to do so by stationary traffic' imply?

A marking indicating 'except when forced to do so by stationary traffic' suggests that under specific circumstances, such as heavy traffic conditions where vehicles are at a standstill, certain stopping regulations can be disregarded. This means that if a driver finds themselves in a situation where they cannot move due to the lack of movement by other vehicles, they are permitted to stop even if the road markings would typically suggest otherwise. This rule recognizes that road conditions can change dynamically and allows drivers to act in accordance with safe driving practices in congested situations.

The framing of the other options does not accurately capture the intent of the marking. Some might imply that drivers can disregard road markings at all times or only stop when traffic is not moving, which misinterprets the conditional nature of the marking. It is specifically about accommodating the realities of traffic conditions, rather than allowing complete disregard for road safety regulations.