Vehicle warning lights

The Illinois DOT past research regarding vehicle warning lights has not been formally documented.
Since the early 1990s, I-DOT has used strobe lights. Prior to that, rotating lights were used. In 2002, the department began to use LED type strobes.

Snow plows, traffic vehicles, and many construction vehicles are required to use lights. Pool cars and administrative vehicles which are not used in work zones on a regular basis are not required to use lights.

I-DOT has experienced radio interference with strobe and LED lights. Generally the lights are quite reliable and not a source of problems. Some early light units had power supply issues as well.

The department does not track the age and effectiveness of lights on state-owned vehicles.

The department does require warning lights for private contractor vehicles in work zones.

The department is open to sharing its specification language.

Strobe-type LEDs are allowed to be the sole warning light on vehicles.

Vehicle warning lights must meet the criteria of the SAE class 1.

Plow trucks have a 96-inch light bar plus stobes mounted near the top of the corner posts of the rear dump body. I-DOT is in the possession of a mix of amber and white lights.