PARK LIGHTING 809 



be delivered readily through its existing transmission system, as required 

 in any park area. The problem under consideration then becomes the 

 generation and source of light and its utilization so as to produce efficient 

 illumination. 



Considerations in Design of the Lighting System 



1. Intensity of Light (foot candles). 



Efficiency of lamp. 

 Efficiency of glassware. 



1. Inaccessibility of dirt and dust. 



2. Ease of cleaning and replacing. 



3. Unbreakableness. 



4. Cost of glassware and its replacement. 

 (c} Appearance by night and also by day. 



2. Standards. 



(a) Appearance. 



(b) Strength. 



(c) Freedom from dirt and rust. 



(d) Safety to public in case of collision. 



(e) Cost of standard and its replacement. 



3. Brightness of Area Illuminated. 



(a) Spacing and height of standards. 



(b) Reflection or absorption of road and other surfaces lighted. 



(c) Visual angle between lamps and surface. 



(d) Eye discomfort and glare. 



(e) Uniformity of illumination along street. 



(/") Contrasts produced on street surface and on objects on the street, 

 (g) General effect and appearance. 



4. Reliability of Manufacturer. 



5. Experiences of Other Systems. 



6. Cost of Current and Maintenance. 



Fixed installation factors. Many of these factors are fixed by the con- 

 ditions which exist in the park system and are not subject to change. 



I. Spacing of light units. In most instances on the parkways, this 

 spacing is influenced and predetermined by the street intersections. These 

 intersections occur almost without exception at distances of either 330 

 feet or 660 feet, and as it is necessary for purposes of economy to place 

 lighting units at the intersecting streets, so as to avail ourselves of the 

 opportunity to light the intersecting thoroughfare as well as the parkway, 

 the spacing of the lights becomes an economical division of these units. 

 For reasons herein explained, the average spacing adopted is 150 to 200 



