What marks the portion of the runway identified by large chevrons pointing in the direction of the threshold bar?

The portion of the runway identified by large chevrons pointing in the direction of the threshold bar is indeed related to blast pads, stop ways, and EMAS systems. These large chevrons serve as visual indicators for pilots, helping them recognize the area where aircraft should not land or where there is additional safety protection provided.

Blast pads are segments at the beginning of the runway that can help with the safe deceleration of an aircraft in the event of an overrun. Stop ways are also designated areas at the end of the runway meant to provide additional space for an aircraft to safely stop if it cannot halt on the runway itself. The EMAS (Engineered Materials Arresting System) is designed to slow down and stop an aircraft that overruns the runway.

Together, these elements play a crucial role in runway design and safety, clearly defining access and operational limits for pilots. This is reflective of the regulatory standards set for airport operations, which prioritize safety by ensuring that critical areas are easily identifiable and properly trained on by pilots and crew members.