Canadian and UN documents listed. Entire document copyedited for grammar, clarity, and up-to-date language. Added Figure 3 for white photometric requirements. Title adjusted.§ 2.2: Added SAE J2040 & J2261. Added UN publications. Updated title and their respective availability of FMCSA publication. Added Canadian publications. Added TTMA publication.§ 3: Separated light function definitions from lamp/device definitions in accordance with recent practice in other SAE Standards. Added "end-outline marker lamp" designation as an alternative term for clearance lamp. Copyedited for clarity.§ 3.6: Stipulated that identification lamps are to appear substantially identical to one another in their group of three: to formalize a longstanding industry practice, in recognition of the ID lamps' unique required aspect of being a group of three devices, and to weigh against temptation to misuse identification lamps as style/fashion toys.§ 5.1 and 6.1: Copyedited for clarity.§ 6.2: White added as an optional color for front clearance and front identification lamps, for alignment with international practice and for consistency in North American practice (with note that as of this document's publication date, F/CMVSS № 108 require yellow for these functions).§ 6.4: Copyedited for clarity. Added 6.4.1 and 6.4.3.1 stipulating operational modes for multifunction lamps.6.4.3.1: Added term "optically".§ 6.4.8: Updated with language that applies to all light sources, rather than just to filament bulbs with indexed bases.§ 6.5: Copyedited for clarity.§ 6.5.2: Correction made for metric conversion error; The corrected value of 38.1 cm is equivalent to the former 15 inch (English unit) requirement.§ 7.1: Copyedited for clarity and to remove ambiguity. Added 7.1.2, noting special installation guidelines for emergency and special-service vehicles.