The SAE Lighting Systems Group have been working to adjust the latest version of J2087, which contains specifications for daytime running lights. Language has been clarified, photometric tables have been simplified, and—significantly—the allowance for producing the daytime running light function with reduced-intensity high beam headlamps has been removed. It will take another affirmation ballot before a new version of J2087 is cleared for publication.
The high-beam DRL was an early placement in the SAE standard, primarily to facilitate easy and inexpensive addition of a DRL function to vehicles without adding a new lighting device. The troubles with obtaining a DRL function by reduced feed to a halogen bulb are bulb blackening due to sub-rated voltage not permitting the halogen cycle to operate, and the cone of illumination narrows as voltage is decreased. So if the voltage is decreased enough to reduce the central intensity below the maximum-permissible 7,000 candela, the DRL is useless at wide view angles. But if there’s enough intensity at wide view angles, the DRL is too glaring straight-ahead. And with LEDs, chopping the feed with PWM can induce distracting flicker visible to other drivers. Now it’s been judged time to withdraw the high beam DRL option.
Of course, SAE standards themselves do not carry legal weight; they’re not regulations, but consensus-devised descriptions of best practice. U.S. and Canadian regulations still permit high-beam DRLs, and there’s no change on that in the foreseeable future. A note at the top of the standard will probably explain that the regulations permit high-beam DRLs, but it is no longer considered as a best practice for use on newly-designed vehicles.