Vehicle warning lights
Arizona DOT Equipment Services tries to adjust flash patterns on vehicle lighting systems to avoid critical flash frequency ranges that may be associated with ‘hypnotic’ or seizure effects.
Arizona Revised Statutes 28-947 defines legal restrictions on lighting on vehicles in Arizona. On non-emergency vehicles, amber lighting is used to front, rear, and sides, with partial red lighting to the rear used on some vehicles in accordance with ARS 28-947D and ADOT SUP-6.10 (see below). Emergency (enforcement) vehicles use red and blue to front, rear, and sides. The entire ADOT vehicle fleet uses a variety of lighting technologies, with much of the fleet currently using 2-unit beacons with halogen rotators (Federal HighLighter or Code 3 LP6105). Traffic Group vehicles use a combination of stationary, rotating, and oscillating halogen lights on most trucks and sedans in order to provide appropriate lighting for varying situations. This provides excellent results in terms of day/night visibility and durability. ADOT is now using more and more LED-based lighting equipment, but still uses halogen lights for rotating beacons.
In ADOT’s experience, focused halogen reflector lamps (rotating, stationary, or oscillating) provide superior visibility/conspicuity compared to any other existing lighting technology under difficult or challenging ambient light conditions such as dawn/dusk backlighting, extremely bright sunlight, etc.
ADOT Policy SUP-6.10 defines supplemental and warning lighting policy for ADOT vehicles. See the web site below.
Traffic Group has nearly phased out the use of strobe lighting due to reliability/durability problems and a less-visible perceived flash in very bright ambient conditions (such as Arizona summer sunshine). Remaining strobe lighting is removed and replaced with halogen or LED lighting at vehicle turn-in / reissue. The remaining ADOT fleet is also phasing out strobe lighting in a similar manner.
ADOT Equipment Services specifies a bright and durable lighting package at initial vehicle issuance, using lights that have been shown to provide adequate performance for the entire service life of the vehicle. Empirical observations have indicated no follow-up studies have been needed.
It is uncertain if lighting is required for contractor vehicles. That being said, most contractor vehicles do display warning lights.
Specification language can be obtained from ADOT Equipment Services.
Although halogens still make up the ‘backbone’ of ADOT’s lighting equipment, LEDs are being used more and more often where appropriate, such as for stationary lamp arrays or high-vibration environments. Although LEDs do not yet equal the combination of intensity and flash duration that halogen lamps provide, LEDs do offer far lower amp draw for comparable brightness and greatly improved vibration resistance.
Approval criteria for vehicle lighting are established in SUP-6.10.
ADOT plow trucks are currently issued with the following lighting package: – Elevated white halogen plow lamps in front – Two 2-unit amber halogen rotator beacons on cab (Federal Highlighter or Code 3 6105) – Four rearward facing PAR46 LED stationary lamp units mounted near the top of the spreader hopper – two on each side, one amber / one red per side, alternately flashing – One 2-unit amber halogen rotator beacon on top of spreader box (Federal Highlighter or Code 3 6105) – All other standard FMCSA truck lighting as appropriate
Dennis Halachoff, ADOT Equipment Services Fleet Manager, will be the ADOT contact for follow-up information. See http://www.azdot.gov/Inside_ADOT/Equipment_Services/fleet.asp for contact information.