Idaho Auxiliary Lights: Two Each, Mounting Heights, Four Lit in Front

The four auxiliary lamp types in § 49-918 each have their own numbers. Spot lamps are capped at two, and each lighted spot lamp must be aimed and used on approaching another vehicle so that no part of the high-intensity portion of the beam is directed left of the prolongation of the extreme left side of the vehicle, nor more than 100 feet ahead. Fog lamps are capped at two and must be mounted on the front between 12 and 30 inches above the surface the vehicle stands on, aimed so that with the vehicle unloaded none of the high-intensity portion of the light left of vehicle centre projects, at 25 feet ahead, higher than 4 inches below the centre of the lamp; § 49-918(2) then expressly allows compliant fog lamps to be used together with lower head lamp beams under § 49-922(2). Auxiliary passing lamps are capped at two and sit between 24 and 42 inches. Auxiliary driving lamps are capped at two and sit between 16 and 42 inches. Both of the last two are pulled into the multiple-beam requirements of § 49-922 for any combination with head lamps.

The hard ceiling most Idaho light bar owners run into is § 49-927(2). Where a vehicle already carries the required head lamps and is also fitted with any auxiliary lamp, spot lamp or other front lamp projecting a beam greater than 300 candlepower, no more than four lamps on the front may be lit at any one time on a highway. Two headlamps plus a pair of driving lamps therefore uses up the entire allowance.

Section 49-928 supplies the aiming and colour limits. Subsection (1) requires any lighted lamp or illuminating device other than head lamps, spot lamps, auxiliary lamps, flashing turn signals, emergency vehicle warning lamps and school bus warning lamps that projects more than 300 candlepower to be directed so that no part of the high-intensity portion strikes the roadway more than 75 feet from the vehicle. Subsection (3) then gives a practical glare test for head lamps and auxiliary driving or fog lamps: a lamp glares if any part of the main beam strikes a person, vehicle, screen or other object higher than the lamp centres at 25 feet or more ahead, and in no event may the main bright portion be higher than 42 inches at 75 feet ahead. Subsection (2) bars driving with any lamp or device showing a red light visible from directly in front unless this title expressly authorises it, and subsection (4) prohibits flashing lights except on an authorised emergency vehicle, a school bus, snow removal equipment, or as a turn indicator or a warning of a vehicular traffic hazard.

Colour is allocated by vehicle class in § 49-910A. Only police vehicles may display blue lights, lenses or globes. Red lights or lenses visible from the front are limited to fire fighting vehicles, volunteer firefighters' vehicles, certified EMS personnel vehicles, ambulances, sheriff's search and rescue vehicles under the immediate supervision of the county sheriff, wreckers as defined in § 49-124 while blocking a lane during a recovery, vehicles authorised by the Idaho transportation board for enforcement under § 40-510, and other emergency vehicles designated by the director of the Idaho State Police. That subsection was last amended by 2025 Session Laws ch. 94, sec. 31. Against those restrictions, § 49-910A(3) is unusually generous: any motor vehicle may carry a flashing amber light to warn of a vehicular traffic hazard, and approaching drivers must yield the right-of-way to a stationary vehicle displaying one.

Section 49-920 adds the small stuff, again by count: not more than two side cowl or fender lamps emitting amber or white without glare, not more than one running-board courtesy lamp per side in white or amber without glare, and not more than two back-up lamps that may not be lit while the vehicle moves forward. Section 49-921 authorises a distinctly Idaho accessory, a rear-mounted acceleration and deceleration system using one green light on the accelerator and up to two amber lights while coasting, mounted horizontally between 20 and 72 inches, one system per vehicle, visible 500 feet to the rear, and approved by the board model by model before it may be sold in the state. Underneath all of it, § 49-902(2) says nothing in chapter 9 prohibits additional parts and accessories that are not inconsistent with the chapter, which is what leaves room for accessory lighting the chapter does not name, and § 49-930(1) requires head, auxiliary, fog and rear lamps and required reflectors to be of a type submitted to and approved by the director, bearing the approval trademark legibly when installed.

Under Idaho Code § 49-236(2), violating any provision of chapters 6 through 9 of title 49 is an infraction unless otherwise specifically provided, and § 49-236(4) routes punishment to Idaho Code §§ 18-111, 18-112, 18-113 and 18-113A. 50. Section 49-902(1) is the charging provision for equipment cases: it is unlawful to drive or move, or for an owner to cause or knowingly permit to be driven or moved, any vehicle in an unsafe condition, or lacking required lamps in proper condition and adjustment, or equipped in any manner in violation of chapter 9.

Idaho conducts no periodic safety inspection, so an auxiliary lighting problem surfaces at a traffic stop rather than in a lane. Selling is separately reachable: § 49-930(1) bars having for sale, selling or offering for sale an unapproved head lamp, auxiliary or fog lamp, rear lamp or required reflector, and § 49-921(7) bars selling an unapproved acceleration and deceleration lighting system model in Idaho.