(WHTM) — School has been back in session for a few months and school buses have taken to the roads. We all know about the flashing yellow and red lights on top of school buses, but, on newer buses, there seems to be an additional light: a strobe light.

So why do buses nowadays have this light on top of them?

According to the Pennsylvania code:

(b.3)  Strobe light.–School buses may be equipped with a bright white strobe light affixed to the roof.

Title 75 Section 4552

Schoolbusfleet.com states that some buses are equipped with this light, but some are not. The light is usually placed on the longitudinal center line of the roof of the bus, and closer to the rear.

Their lens is usually clear but sometimes can have an amber tint. The main reason for the lights is to improve safety and increase the visibility of the school bus, especially in foggy conditions or inclement weather. Because of the intense flashing light, it grabs the attention of motorists.

Besides the white strobe lights, school buses have other flashing lights such as yellow or amber lights or red flashing lights. Unlike the white flashing lights on the roofs, these colored strobe lights are always on buses.

The amber flashing lights indicate that the school bus is preparing to stop to either unload or load. This is when drivers should begin to slow down, according to Pennsylvania State Police. If the red lights are flashing, you must stop, as children will be either getting on or off the bus.

Motorists must stop at least 10 feet away from school buses that have their red lights flashing and stop arm extended, according to PennDOT.

More information on bus safety can be found here.