In many states of the USA, school buses are fitted with a "roof-mounted strobe".
In some states, they are required by law:
Mike Simmons, state director in Arkansas, says that the state's School Bus Safety Act of 1995 mandated that all school buses be equipped with a strobe as well as a crossing arm beginning July 1, 1997.
In some states they are not required, but often found:
Some states that don't require the strobes still see widespread use of them. For instance, Indiana doesn't have a strobe mandate, but state director Pete Baxter says that a survey in 2000 found that about 78 percent of the state's school buses were equipped with them.
The local states also vary about the conditions under which they may be used.
In California, school bus drivers may only use the strobes when visibility is reduced to 500 feet or less due to such atmospheric conditions as fog, rain, snow, smoke or dust. The conditions do not include the darkness between a half-hour after sunset and a half-hour before sunrise.
In Michigan, school bus drivers may only use the strobes during inclement weather, loading or unloading of passengers, hindrance in visibility of the bus or, unlike California, a half-hour after sunset until a half-hour before sunrise.
There are claims that these devices improve safety:
Kent Chapman, who handles fleet maintenance and dispatching at the district, says the strobes' benefit is clear. "It's an attention-getter — it makes [motorists] aware that there's a vehicle ahead that is probably traveling slowly," he says.
Is there good evidence to support the claim that roof-mounted strobes on school buses improve safety?