Final answer:
The Khumbu Icefall is referred to as a "toll road" because it is a dangerous and congested section where climbers have to wait in long lines.
Step-by-step explanation:
The Khumbu Icefall is referred to as a "toll road" because it is a dangerous section of the mountain where climbers often have to wait in long lines to pass through. This term is used metaphorically to describe the challenging and congested nature of this part of Mount Everest. It is not a paid route and does not involve a fee to use the Khumbu Icefall.