What is the purpose of a runway lane?

A runway lane is specifically designed as a safety feature on grades where trucks may experience brake failure. The main purpose of a runway lane is to provide a safe area for trucks that are unable to stop due to failed brakes, allowing them to gradually slow down and come to a stop without posing a danger to themselves or others on the road. This is particularly crucial on steep hills or slopes where a truck's momentum can increase significantly, making it difficult to control its speed using brakes alone.

The other choices do not accurately express the primary function of a runway lane. Providing a space for vehicle parking relates more to rest areas than to safety mechanisms like runway lanes. Assisting trucks to boot up on hills is not the purpose of a runway, as they are not designed to aid in starting movements but rather in stopping. Likewise, while runway lanes might have some minor impact on guiding vehicles in adverse weather conditions due to their visibility and designated escape route, this is not their primary purpose. The focus is specifically on serving as an emergency stop for vehicles facing brake issues.