From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Page discussing headlighting performance on wet roads and the development of transcontinental highways.
| Identifier | ExFiles\Box 37\1\ scan 159 | |
| Date | 1st July 1927 | |
| Vol. XXI July, 1927 No. 1 27 WET ROADS AND HEADLIGHTING curb due to the wet road as well as the increased glare. Photometric measurements on both asphalt and concrete roads, made by Mr. Porter to show the effect of a wet road on intensity of both the upper and lower beam and to compare the two types of road surface, indicate relatively the same effects noted in the laboratory work described but show little difference between the effects of a concrete and an asphalt road-surface. From this work Mr. Porter concludes that most of the reflection comes from the surface of the water which, in the case of concrete, fills up the depressions. GOOD RESULTS WITH AUXILIARY DRIVING-LIGHT In endeavoring to set up a system of light-distribution which would give satisfactory results as regards glare and visibility on wet roads, various combinations of symmetrical and non-symmetrical beam were used. When using only two 21-cp. incandescent lamps, we were impressed with the lack of light flux necessary to meet the requirements. With a limited light-output it is obvious that the light-distribution throughout the beam must be a compromise between the high-intensity driving-beam and the wide and lower-intensity portion desirable on curving roads and when turning corners. One system which proved satisfactory was obtained through the use of three head-lamps. The two outer lamps were equipped with lenses having a 40-deg. spread and gave a relatively deep beam with an intensity of approximately 5000 candles. This beam was aimed so that the top met the road 100 ft. ahead of the car. The beam from the third head-lamp had a spread of about 6 deg. and was aimed with its top horizontal and pointed straight ahead of the car to provide a good high-speed driving light. By a two-filament lamp properly adjusted this top beam could be depressed slightly and shifted to the right. This combination was less glaring and gave better lighting on the right side of the road than our standard system. A number of other combinations were tried but unfortunately weather conditions did not permit recording test data or taking photographs, hence a complete report on this phase of the work cannot be made at this time. CONCLUSIONS DEDUCED FROM THE TESTS As a result of this investigation, supplemented by a considerable amount of driving on wet and dry roads, the following observations are made: (1) Comparing wet and dry roads, the effect of the wet road-surface is to change the light-distribution materially, resulting in greater glare with its consequent interference with vision (2) Meeting a given light-distribution, higher light-intensities are required to reveal an object on a wet road than on a dry road, due to greater interference with vision and also to change in light-distribution (3) Increasing the light-intensity in a symmetrical system does not give greater revealing power (4) The use of a non-symmetrical system in which the high-intensity portion of the beam is directed to the right of the car axis reduces glare and affords better vision (5) Rigid adherence to the use of two 21-cp. lamps has resulted in insufficient light-flux being available to meet all requirements. It is believed that more light could be used to advantage in providing a distribution better suited to meet varying road and weather conditions (6) The use of a very wide-spread low-intensity beam near the car, in conjunction with a relatively narrow controllable high-intensity driving-beam, seems to possess advantages for both dry and wet roads (7) With reference to the low-intensity beam referred to in (6), which corresponds in aiming to the present depressed beam but has much lower intensity and wider spread, we know of no reason why fixed-focus design should not be used with a somewhat longer focal-length than the present standard and employing suitably designed reflectors or lenses (8) The use of auxiliary driving-lights in which the beam is directed to the right of the car axis should be encouraged. In addition to affording better view of the right side of the road, this brightly lighted area tends to keep the driver's eyes directed away from oncoming lights, which is an advantage TRANSCONTINENTAL HIGHWAYS DURING the last year, additions to the Federal-Aid system of highways totaled 9400 miles, bringing the aggregate Federal-Aid improved highways to 55,903 miles. Equally important extensions have been made to the State primary systems and, in particular, to the main East and West and North and South roads. An outstanding route, because of its significance as a mid-continental connected highway from Atlantic City, N. J.{Mr Johnson W.M.}, to San Francisco, is United States Highway No. 40. This touches such important cities as Baltimore; Wheeling, W. Va.; Columbus, Ohio; Indianapolis; St.{Capt. P. R. Strong} Louis; Kansas City, Mo.; Denver; Salt Lake City; and Reno, Nev. The entire length is 3220 miles and the route is paved throughout from Atlantic City to St.{Capt. P. R. Strong} Marys, Kan., a distance of 1302 miles. West of St.{Capt. P. R. Strong} Marys, the roadway is chiefly graded earth or gravel, except between Auburn, Cal.{Mr Calvert}, and San Francisco, where there is a continuous stretch of pavement. This route crosses the Great Salt Lake Desert over the famous Wendover cutoff. Another route of importance is No. 30, which extends from Atlantic City, N. J.{Mr Johnson W.M.}, to Portland, Ore. It coincides with the Lincoln Highway between Philadelphia and Granger, Wyo. In passing through Pennsylvania the route touches also Lancaster, Gettysburg, Chambersburg and Pittsburgh, but passes through no large city in Ohio and bypasses Chicago through Chicago Heights and Joliet to Aurora, Ill. At Granger, Wyo., Route No. 30 divides into 30 North and 30 South, the southern branch going through Evanston, Wyo., to Ogden, Utah, while the northern division continues into Idaho through Montpelier and Soda Springs, Idaho. At Pocatello the route follows the Snake River somewhat closely, and in Nebraska, Idaho and Oregon it coincides with the old Oregon Trail. This route is improved with gravel, bituminous macadam, or smooth pavement as far as Wheatland, Iowa, and from Border, Wyo., to Portland, Ore., with varying stretches of gravel or pavement. Nearly 90 per cent is surfaced. Route No. 20 will carry the motorist westward from Boston through Albany, N. Y., to Buffalo, and then over a highly improved Canadian road to Detroit. The tourist who seeks a route to follow still farther westward may take No. 10, through Saginaw to Ludington, Mich., where Lake Michigan is crossed by ferry to Manitowoc, Wis., and then touching Minneapolis; Fargo and Bismarck, N. D.{John DeLooze - Company Secretary}; and Billings and Missoula, Mont., to Seattle. About three-fourths of this route is surfaced.—American Motorist. | ||