Final answer:
A runway VASI system provides visual guidance to pilots during approach and landing on a runway.
Step-by-step explanation:
A runway VASI system provides visual guidance to pilots during approach and landing on a runway. VASI stands for Visual Approach Slope Indicator and it consists of a series of lights installed on both sides of the runway.
These lights provide a visual indication to the pilot on whether their aircraft is above, below, or on the correct glide slope for a safe landing. The VASI system helps pilots maintain the proper vertical descent path and aids in preventing runway overruns or undershoots.