1925-01-01

FUNDAMENTAL PRINCIPLES OF AUTOMOBILE HEADLIGHTING 250053

After referring to the recommendations made to the National Conference on Street and Highway Safety by the Committee on Motor Vehicles and the Committee's further explanation of the recommendations, the author amplifies more fully the difficulties that have arisen in the operation of the system of headlight regulations sponsored by the Illuminating Engineering Society and this Society and suggests a line of fundamental research with a view to drafting more desirable regulations. Inasmuch as road conditions have changed greatly since the regulations at present in force were first proposed, he believes that a new study of the subject might result in marked improvement.
Definite control of a concentrated headlight beam, deflected below a horizontal line, as originally proposed by the Society, failed to produce the desired result, and the next step was the formulation of the regulations listed in the S.A.E. HANDBOOK.
But these regulations are most effective on a perfectly level road surface and are upset by slight variations in road contour or of car loading; the close adjustments required can be produced only by fairly expensive equipment that is not maintained long in adjustment by the user; enforcement of the regulations is difficult because a head-lamp may get out of adjustment soon after it has been checked. Tilting, as a cure for these difficulties, results only in excessive illumination of the roadway in front of the car and renders the driver almost entirely oblivious to objects beyond.
On narrow crowned roads or on narrow roads with low shoulders, the act of turning out produces a lateral tilting of the car that is sufficient to bring some of the rays within the oncoming driver's vision at close range.
No concrete recommendations are made by the author but further research is suggested to determine the ability of the eye to see under a wide variety of light-distribution. Reference is made to the possible desirability of placing maximum values on supposedly non-glaring beams deflected below the horizontal; of using diffused lighting on vehicles of moderate speed; of mounting lamps asymmetrically; of employing only the right headlight, the left lamp being entirely extinguished and a marker-light being used in its place; of making use of only a single head-lamp mounted on the right side of each car, or a high-power lamp on the right side coupled with a lamp of moderate power throwing a diffused light on the left side, or vice-versa, the left lamp being controlled as to elevation and limited as to candlepower; and of adopting the so-called “courtesy” light.

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