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The photographs in figures 7 and 8 offer dramatic evidence of the windshield reflectances shown in Table III in the columns labeled dash reflection. Figure 7 shows a man standing on a tree-covered street. The photograph was taken with black velveteen lying on the dash top. Figure .8 shows the same scene without the velveteen light absorber. As a pedestrian in broad daylight, he wouldn't suspect that he was invisible to the driver.
To achieve optimum visual performance at distance the automobile driver must be provided a daytime highway scene with the controllable items in the field of view adjusted to hold brightness levels equal to or lower than the average scene brightness but not lower than 1/10. Since the average scene was measured in this study to be 11.7% of the outside natural illumination, all objects receiving direct sunlight, e.g., the hood, the steering wheel, wiper blades, etc., should reflect not more than 10%. Comer posts and automotive interiors not receiving direct illumination should be of high reflectance values to keep away from excessively dark objects anywhere in the field of view. The surfaces reflecting in the windshield, however, must be as black and dull as possible to control veiling glare.
So that the driver may achieve optimum visual performance in reading the instruments of the dash panel, the instruments should be equal to or brighter than the immediate surrounding panel by an amount of up to 3 to 1 but not brighter than 10 to 1. Furthermore, to make it possible to adapt quickly from far seeing to dash panel seeing, illumination on the dash panel must be improved. A value to strive for is not less than 1/3 of the average outdoor scene brightness. Summary and Conclusions: A. This study on windshield and instrument panel characteristics has shown:
1. All of the fifty-six 1959-62 automobiles tested had serious faults so far as the visibility of the highway and the instrument panel in the daytime is concemed.
2. The amount of light reflected from the top of the dash onto the windshield and into the eyes of the driver averages over 15% of the average scene luminance.
3. The amount of light scattering dirt on automobile windshields is small, and variable as one would expect, averaging only 4.8%.
4. Glare sources of exceedingly high intensities were noted and all cars tested had chromium trim of various types in the field of the view of the driver.
5. Dash panel instrument illumination was generally much too low in the daytime to permit the meters to be seen at a glance. This is in addition to the problem in 4 above which further interferes with quick seeing B. Every vision engineering defect noted in this study can be remedied by the automobile manufacturers by practical and economical changes. Specific recommendations are made in the text.
1) Allen, Merrill J., Certain Visual Aspects of the Modem Automobile, Joumal of the American Optometric Association, December 1962.
2) Allen, Merrill J., A Study of Visual Performance Using Opthalmic Filters. ASD Technical Report 61.576, pp. 21-26, October 1961, United States Air Force, Wright-Patterson Air Force Base, Ohio.
3) Borish, Irvin M., Clinical Refraction, Chicago, The Professional Press, 1949, Pg. 110.
4) Duke Elder, Sir W. Stewart, Textbook of Ophthalmology, Mosby Co., Vol. IV, 1950, Pg. 4492
5) I.E.S. Handbook, 3rd Edition, Illuminating Engineering Society, 1860 Broadway, New York, New York, 1959. Sect. 12, Pg. 6; also see Sect. 2, Sect. 14, Pg. 3, Sect. 15, Pg. 3.
sunt sky illuminance)
FIGURE | SOURCES OF WEILING GLARE IN AN AUTOMOBILE WINDSHIELD
TABLE I. Specific Automobiles Studied.
Car Make Year
Model Windshield Color of Dash Dr.-Car Time Sky 1 Chevy | 1962 II-400 Nova Clear
Royal Blue W 12:35 Mear 2_Cher 1960 Biscane Sedan Clear
Royal Blue SW 11:12 Clear 3_Chevy 1961
Royal Blue SW 12:15 Clear 4 Chevy 1962 4-Door Sedan Clear Mod.-Drk.Grey SE 2:15 Clear 5 Chevy 1962 Impala Hardtop Gradient Maroon
SW 3:25 Clear 6_Chevy 1962 Impala Hardtop Clear Med, Drk. 0. Crn N 5:00 Lt. Haze 7 Chevy I 1961 hoDoor Sedan Cloar Forest Green N
4:15 Clear 8 Cher 1962 Ipala Hardtop Gradient Med.-Lt, Bronze N
1:30 Clear 9 Chevy 1 1962 Corvair 700 Clear Drk.Beige N-NW 4:05Mear 10 Chevy 1962 Corvair 700 Mear Drk.Beige W
4:35 Cloudy 1 Chevy 1 1960 Corvair Clear
SW 10:40 Clear 112_Chew 1961 Corvair Monza 900 Clear Beige
E 4:25 Clear 13 Ford 1962 Sports Coupe Clear Are Eng. Rod S
9:20 Clear Ford 1962 Galaxie Sedan Clear Blue-Green E 2:10 Clear 15 Ford 1961 Galaxie Hardtop Clear
Black SW 12:50 Clear 16 Ford 1961 Falcon 2-Door
2:15 clear 17 Ford 1962 Falcon 2-Door Clear Black 1 3:20 Clear 118 Ford 1961 Falcon Sta. Wagon Clear Med. Blue N
9:50 Clear 19 Ford 1960 Sunliner Convert. Clear
S 11:30 Clear 20 Ford 1960 Convert. Too Town Clear Fire Eng. Red N
1:35 Clear 21 Ford 1960 Fairlane 500 Clear Forest Green N
5:15 Cloudy 22 Pont. 1962 Star Chief Sedan Gradient :-Brun; ?-Tan E
2:25 Clear 23 Pont. 1962 Grand Prix Hdto. Gradient T-Maroon;B-Red E 12:20 Lt. Haze 244 Pont, 1960 Star Chief Sedan Gradient Pea Green
2:55 Play 125 Pont. 1961 Bonneville Convert Gradient T-Ry].Bl;A-Bl. SW 10:00 Clear 126 Pont. 1961 Tempest Sedan Gradient Drk. Royal Bl S
Clear 27 Pont. 1961 Temoest Sedan Gradient T-Wine; B-Red E 5:00 Clear 28 Clds. 1961 2-Door Hardtop Gradient T-Brwn; Tan P. N 10:45 Mear 29 clds. 1961 88 2-Door Hardtop Gradient T-Brwn; Brz.P. SW 1:35 Clear 30 olds. 1962 Super 88 Sedan Gradient T-RYL. BI, Bl. P. N
9:00 Clear 31 Olds. 1962 88 4-Door Sedan Gradient T-Maroon; Red P. W
3:30 It. Haso 32 olds. 1962 Starfire Hardtop Gradient Tkaroon; Red P. N 10:45 Clear 33 Buick 1962 4-Door Sta. Wagon Gradient T-Ryi. Bl; B2. P.
11:55 Clear 34 Buick 1961 Invicta Hardtop Gradient T-Brwn: B:. P. E
2:00 Lt. Hazel 35 Cad. 1962 4-Door Hardtop Gradient Black
44:20 Clear 36 Dodge 1962 Lancer Hardtop
Clear Forest Green E 12:32 Clear 37 Dodge 1962 Lancer Sedan
Medium Blue W-SW 2:10 Clear 38 Dodge 1962 Dart 440 Sta. Wagon Clear Rose Beige
3:00 Clear 39 Dodge 1962 Dart 440 Sta. Wagon Clear Rose Beige S 12:15 Cloudy 40 Plmth. 1961 Valiant Sedan Clear Medium Blue S
4:00 Clear 41 Amblr. 1962 American Sedan Clear Medium Green W-SW 3:10 Clear 442 pumblr. 1962 American
S 11:50 Clear 43 Rmblr. 1962 Classic Sta. Wagon Clear Medium Bluo S
1:35 Mear 404 Rmblr. 1962 Classic Sedan Solex Medium Blue E
11:30 Mear 415 Amblr. 1962 Classic Sta. Wagon Clear
E 10:50 Cloer 146 Stökr. 1962 Lark Sedan Clear I-Drk.BG;BG. P. E 11:25 Cloudy 47 Stbkr. 1962 Lark Sedan Clear
Royal Blue E 12:20 Clear 48 Stbkr. 1962 Lark raytona Hdtp. Clear T-Red; Brwn. P. S
3:15 Clear 119 Chrys. 1962 Newport Hardtop Gradient Charcoal
S 4:25 Cloudy 50 Chrys. 1960 Newport Hardtop Gradient Charcoal
4:00 Clear 52 Chrys. 1960 Imperial Hardtop Gradient Dark Brown N-NE 2:50 Clear 52 Rnlt. 1961 Dauphine Sedan
NE 1:30 Clear 53 ww 1962 2-Door Sedan Clear
N 11:50 Clear 54 Merc. 1962 Comet Sedan Clear Fire Eng. Red W-NW 1:30 Cloudy 55 Merc. 1961
Monterey Sedan Gradient Med.-Nrk. Beige NE 12:00 Cloudy 56 Merc. (1962 4-Door Sta. Wagon (Gradient Med.-Nrk. Brow N W 4:10 Lt. Han Abbreviations: Dir.. Direction; T.- Top; B.- Bottom; P.- Panol.
TABLE II. Average Scene % Reflectance
Earth Surface Concrete Road
Dirt Green Field
Blacktop Gravel Parking Concrete
Dirt Green Field Gravel Road
Blacktop City Street City Street Av. Scene