Unlike red and blue emergency lights installed on emergency and police vehicles, amber lighting on service vehicles serve to advertise your vehicles presence. This is unlike emergency vehicles because without having to legally yield the right of way, other drivers are still made aware of the presence of the service vehicles.
Crucial for working plows, tow trucks, high maintenance and pilot vehicles, amber light displays let other drivers know you are there. This helps avoid serious and even fatal accidents, making your presence known and the need for cautious procedure or vehicle operation.
A private snowplow, for example, is backing in and out of driveways clearing customers’ driveways regularly to clear snow. On a snowy February evening, it can be very difficult for passing motorists to see a snowplow about to pull out in front of them, causing a serious accident. Amber emergency lighting literally signals to other drivers to heed caution and process slowly around this kind of indicator.
Then there are municipal snowplows, typically much more immense than the typical passenger vehicle. With amber caution lighting, other drivers know a huge working vehicle is in the area. This lets them know to either get out of the way, pass with caution and to mind potentially visibility-compromising side-splash and/or spreading rock-salt.
Why other drivers on the road are made aware to the caution needed to vehicle near amber emergency lighting has everything to do with psychology. Whereas red and blue lights, combined with strobe and flashing, installed on emergency vehicles alert others on the road to urgently make way, while single beacon amber lighting subconsciously alerts the driver. This is because amber lighting has lower detection than red or blue, but is still bright enough to trigger the need for caution in the perceiver.