PARK LIGHTING 813 



line of the roadway at points opposite lamps and at quarter points between 

 lamps. Horizontal illumination and a test plate on the surface of the road- 

 way was the basis of all readings. 



Conclusions from demonstrations. A study of the records and summary 

 of the readings made will show that having certain fixed and unchangeable 

 factors relating to mounting heights, spacing, reflecting powers of pave- 

 ment and lack of reflection from adjacent buildings, we selected for demon- 

 stration those luminaires which would give a fair average of intensity con- 

 sistent with our requirements, but which at the same time presented a 

 considerable range in uniformity. Varying in uniformity from 4.3 to I to 

 32 to I, the lighting fixtures demonstrated were selected from commercial 

 products of reasonable cost, any of which are and will be available for use. 



As previously stated, intensity and uniformity can be and were meas- 

 ured, but "effective illumination" is a matter of human reaction deter- 

 minable by observation not of one, but of many. 



We appreciated that the illuminant to be chosen for boulevard light- 

 ing must give a satisfactory distribution of light on the road, an acceptable 

 uniformity or ration of maximum to minimum foot candles on the road 

 surface so as to eliminate eyestrain, and a high minimum between stand- 

 ards so as to provide adequate illumination at this point. What is effective 

 illumination, however, must be decided by observation and the demonstra- 

 tion permitted us to receive from those concerned definite opinions as to: 



1. Lack of glare, or interference of source of light with illumination 

 on roadway. 



2. Visibility of curb lines. 



3. The visibility of objects on the sidewalks. 



4. The visibility of objects on the road. 



5. The ease of discrimination by direct illumination. 



6. The ease of discrimination by silhouette. 



7. The general appeal of the various units and the illumination pro- 

 duced on a part of the boulevard where all of the fixed factors prevailed. 



The general consensus of opinion, after repeated viewing under differ- 

 ent conditions of weather, and both with and without traffic on the thor- 

 oughfare, was: 



That the mounting height of 21 feet was the most acceptable, because 

 of freedom from glare and ease of discrimination on sidewalks and roadways. 



That because of ease of discrimination both by direct illumination and 

 by silhouette and because of general appearance and pleasing reaction, the 

 General Electric Company No. 25A with asymmetric refractors and the 

 Westinghouse Company Multilux with Holophane Superlux refractors were 

 the most satisfactory. 



