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Thread: DOT requirements for reversing or backup lighting

  1. #1
    Flashaholic*
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    Default DOT requirements for reversing or backup lighting

    What are the DOT requirements for reversing or backup lighting for a passenger vehicle?

    Other than being white, having at least 1, and only working while in reverse, I can't find any DOT beam or other requirements. Is there a SAE spec that DOT leans on?

  2. #2
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    Default Re: DOT requirements for reversing or backup lighting

    +1 on that; I'd like to know, too. I've seen lots of pickups with a pair of PAR36 tractor floods (very common on a hunter's 4x4), even set up some trucks of my own with anywhere from two tractor floods to four high wattage floods. These are great up in the woods, when you have to turn around in the dark or work behind the truck.

    I want to add some really bright backup lights to our everyday cars. I'm wondering if there are restrictions that will limit me to "offroad only" with these.

    My preference when setting up my old backwoods trucks, is separate manual switching of both bumper level and high level rear lighting. I'm thinking that on an everyday car I'd want a double throw center off switch set up so I have "Manual-Off-Auto," letting me turn them on for work lights, let them work automatically with the stock backup lights, or leave them off.

    I wonder if separate switching changes the legal status of rear floods, making them "work lights" instead of reverse lights.

    Naturally, manual switching would get you into trouble with the law if you turned them on while moving forward on a public road, but it sure is handy when loading firewood at night in the woods.

    BTW, I once specified (and picked up in Alabama, drove home and used for some years) a medium truck based EHD Aid Vehicle that had three dual halogen bulb Whelen Scenelights on each side, four of same on the rear, and even two of them on the front corners of the box. Borrowing an idea from Bellevue, WA Fire Dept, I had it set up so ALL of them come on when the vehicle goes into reverse. Trust me, even at a hectic scene, you can't miss that rig going into reverse.

    FWIW, my 1978 Saab 99 Turbo had backup lights on all four corners. The lights on the front corners shone back and to the sides, very nice for parallel parking.
    Last edited by Hamilton Felix; 12-28-2011 at 11:07 PM.
    There are two kinds of light - the glow that illumines, and the glare that obscures. ~James Thurber

  3. #3

    Default Re: DOT requirements for reversing or backup lighting

    "Backup lamps", as Federal Motor Vehicle Safety Standard 108 calls them, must conform to SAE J593c (February 1968) and the following provisions, which I have copied directly from FMVSS 108:

    <begin cite from FMVSS 108>

    Test points (45L,5U); (45L,H); (45L,5D): Min 45cd total for group

    Test points (45R,5U); (45R,H); (45R,5D): Min 45 cd total for group

    Test points (30L,H); (30L,5D): Min 50cd total for group

    Test points (30R,H); (30R,5D): Min 50cd total for group

    Test points (10L,10U); (10L,5U); (V,10U); (V,5U); (10R,10U); (10R,5U): Min 100cd total for group

    Test points (10L,H); (10L,5D); (V,H); (V,5D); (10R,H); (10R,5D): Min 360cd total for group

    When 2 lamps of the same or symmetrically opposite design are used, the reading along the vertical axis and the averages of the readings for the same angles left and right of vertical for 1 lamp shall be used to determine compliance with the requirements. If 2 lamps of differing designs are used, they shall be tested individually and the values added to determine that the combined units meet twice the candela requirements. When only 1 backup lamp is used on the vehicle, it shall be tested to twice the candela requirements.
    <end cite from FMVSS 108>

    I don't have a copy of J593c/February 1968, but I do have the September 2005 version which has the same zone groups and zone minimum requirements, and also specifies minimum candela values at each test point as follows:

    (45L & 45R, 5U & H & 5D): 15 cd at each point
    (30L & 30R, H & 5D): 25 cd at each point
    (10L & 10R, 10U): 10 cd at each point
    (10L & 10R, 5U): 20 cd at each point
    (H & 5D, 10L & 10R): 50 cd at each point
    (10U, V): 15 cd
    (5U, V): 25 cd
    (H, V): 80 cd
    (5D, V): 80 cd

    It also specifies that when using the zone group requirements, no single test point shall be less than 60% of the individual test point minimum.

    It also specifies maximum anywhere at H and above:
    300cd for a lamp used as part of a 2-lamp system
    500cd for a lamp used singly

    I don't know that these provisions are present in the earlier version of J593, but I think they probably are. That maximum above horizontal is a glare-prevention measure, and it's a sensible one. You're going to turn on white lights at night; you don't want them shining uncontrolled amounts of light in other drivers' eyes. I can think of a lot of fog lamps that would comply with the spirit and often with the specs of the J593/FMVSS108 requirements for backup lamps, and would give you a lot more light than a vehicle's ordinary factory-equipment backup lamps.
    Last edited by -Virgil-; 12-28-2011 at 11:58 PM.

  4. #4
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    Default Re: DOT requirements for reversing or backup lighting

    Hmm... more minimums than maximums. That sounds good. I agree, the max for upward glare makes sense. And I have to agree about fog lights. I've used fogs as rear lights. The spread from a fog pattern gives you pretty much what you want in a backup light. I recall using some old Per-lux "Fogcutter" lights inside the bumper of my International, which is used mostly offroad. They came with, if I remember correctly, a 75 watt PAR36 #4675 bulb in a fog pattern. I even ran across the same pattern in a 100 watt PAR36 bulb, though I doubt it had the same filament shielding. We used them in the "docking light" location of the small boats we drove to and from work at Ross, though we used them more like headlights. The old sealed beam "fog" pattern was more like 50 degrees wide, as opposed to the remarkable 120 degree width of the Cibie 175 fog pattern.

    Such lights make great offroad backup lights.

    High level floods were more useful for actually working behind the truck. And they helped when hitching up a trailer.

    I've often said that the only uses I could think of for cheap fog lights would be backup lights if they're clear and emergency flashers if they're yellow. (Generally, I despise cheap fog lights, but I hate to throw anything away.)

    My concern with backup lights took a surge last February, when a lady in a dark PT Cruiser succeeded in pulling behind me without being seen, by virtue of driving without headlights in a dark parking lot while I was slowly backing out of my space with the Crown Victoria. I was actually looking over my right shoulder, and thought I should have seen her through the right rear window or the corner of the rear window, as she came from my right. But the windows have a bit of tinting, it was pretty dark, she was moving significantly faster than I was (we're still taking 2 mph vs 5-6 mph, I think), and was too busy lighting a cigarette to bother with turning on her headlights.

    I've been wanting to hang 2 or even four very small bright lights on the trailer hitch receiver of the Corolla, and do the same on the Vic as soon as I install its Class III receiver. The WJ Grand Cherokee has a more hidden receiver, but I have something similar in mind there, too. I'd run a separate circuit and use a relay, so current draw isn't critical. But being seen and seeing what's behind me is.

    You know, my old Saab had the right idea. I appreciated the backup lights on the front corners. Apparently there's no law saying backup lights can only be on the back end of the car.

    Trying to interpret the above, it would appear that so long as one doesn't produce a lot of upward glare, one could still put a lot of light below horizontal and on the ground and be within the rules.
    Last edited by Hamilton Felix; 12-29-2011 at 11:40 AM.
    There are two kinds of light - the glow that illumines, and the glare that obscures. ~James Thurber

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