Swedish traffic light (left) for use by public transport vehicles only. All signals use white lighting and special symbols (S, – and an arrow) to distinguish them from regular signals. The small light at the top tells the driver when the vehicle's transponder signal is received by the traffic light.
https://en.wikipedia.org/wiki/Traffic-light_signalling_and_operation
1 Flashing yellow lights mean a bus is going to stop. A driver behind the bus must slow down, prepare to stop, and not attempt to pass the bus. Oncoming cars must drop speeds to 20 miles per hour or less.  When a stop arm is out, every driver, behind the bus or oncoming, must come to a complete stop.
http://www.thegazette.com/2012/08/09/police-remind-drivers-of-penalties-for-breaking-school-bus-laws
Cupertino, California, also used a 4-lamp signal, with a steady red arrow, a flashing red arrow, a steady yellow arrow, and a steady green arrow; during the permissive turn, the flashing red arrow is displayed.
https://en.wikipedia.org/wiki/Traffic-light_signalling_and_operation
In many parts of Western Europe transit signals (for trams, and in some cases buses as well) employ traffic signals that are phased similarly to main traffic signals but replace the green light with a vertical white bar, the red light with a horizontal white bar and the yellow with a white dot or diamond.
https://en.wikipedia.org/wiki/Traffic-light_signalling_and_operation
This, and a shorter, more optimistic time of 1.5s, will be used in the analysis. It is preferable that the motorist does not brake heavily because this may be a hazard to following traffic and it could also lead to reluctance to slow down if school buses with lights flashing are repeatedly encountered on the road.
http://users.tpg.com.au/users/mpaine/buslight.html
In New Zealand, red and yellow arrows (where fitted) always display regardless of the aspect main light. When a road is given a green light from an all-turn direction stop, a red arrow continues to display to turning traffic, holding traffic back while the pedestrian crossing on the side road is given a green signal.
https://en.wikipedia.org/wiki/Traffic-light_signalling_and_operation
The Australian Vehicle Standards Rules 1998 require bus flashing warning lights fitted. after June 1999 to have minimum intensities similar to those shown in Table 7, except that maximum intensities for locations more than 5 degrees below the horizontal are not specified.
http://users.tpg.com.au/users/mpaine/buslight.html
The double-red ball aspect is used in Saskatchewan and Alberta, Canada, to indicate a protected-prohibited left turn signal. A sign with the universal no left turn symbol and a depiction of the double red light is mounted near the signal to indicate that no left turns are permitted on a double-red light.
https://en.wikipedia.org/wiki/Traffic-light_signalling_and_operation
Here is the break down of simple rules you need to know to keep children safe this school year: Flashing yellow lights mean a bus is going to stop. A driver behind the bus must slow down, prepare to stop, and not attempt to pass the bus. Oncoming cars must drop speeds to 20 miles per hour or less.
http://www.thegazette.com/2012/08/09/police-remind-drivers-of-penalties-for-breaking-school-bus-laws
Many school buses in the USA are fitted with bright red and yellow flashing warning lamps. SAE Standard J887 School Bus Warning Lamps (SAE 1987) which sets out requirements for these signal lights, including photometric performance. The signal units are tested at operational voltage (e.g 12.8V or 25.6V).
http://users.tpg.com.au/users/mpaine/buslight.html
what do flashing yellow lights on a bus mean
Flashing yellow lights mean a bus is going to stop.