Question:

You are following a school bus. Its yellow lights start flashing. What does this mean?

A The bus is preparing to stop for passengers; you must slow down and prepare to stop.

Explaination

Just before a school bus stops for passengers, the bus driver will switch on flashing yellow lights. Slow down and prepare to stop. When the school bus's red lights start flashing, you must stop at least 20 feet from the bus. [School Buses, Chapter 6 Passing, Part 2 - Rules of the Road, New York State Driver's Manual]