Motorists and pedestrians are the greatest threat to emergency vehicle responses. Depending on other drivers to detect and safely yield an approaching emergency vehicle is crucial to collision prevention. Their visible detection relies on a combination of the vehicle’s perceivable size, luminance and color prominence against a background.
Flashing lights are proven to garner the attention pf other motorists on the road. This is especially true when lights visible from the same side of the vehicle flash in unison, creating an outlining effect of the vehicle. This is important to demonstrating to the observer the larger size of the vehicle.
Achieving this essential presence- studies show- requires more than red flashing lights. Lights of this color alone do not offer optimal visual cues. This is mainly because red is not only weakly visible, its perception is also easily lost in other tail lamps on vehicles and psychologically identified with rage and passion.
Combinations with other, more visible colors may improve overall lighting effectiveness. Human vision sensitivity peaks in yellow-greenish light, for example, though white is the most visible and effective for gaining attention as warning lights. But white fails to identify the vehicle and subsequently rarely used alone. Green is highly visible but associated with authorization to “go” and being a “safe,” color.
Studies show a driver’s visual field is mostly peripheral so the strobe white light effect is imperative for initial attention-gaining effect. A strobe’s high output would be expected to compensate its brief flash duration. But since red, white and orange are less visible than lime-yellow, combining colors to capitalize on both visibility and identification is most often recommended.