Control Circuits

There are several methods used to control the operation of area lighting systems. For recreational lighting, only a manual switch is required. On the other hand, streetlights and security lights have more sophisticated controls.

Lights normally are on during the hours of darkness or when unusual weather conditions indicate the need for artificial light. Although lights could be activated by assigning an individual to manually operate the controls, they are usually turned on and off by a combination of controls.

Most control circuits that you will encounter in the field use one of the following devices to control the lighting system: photoelectric cell, cadmium sulphide cell, time clock, pilot wire relay, or cascading relays. A detailed description

Table 1-1.\Approximate Lamp Capacity for Streetlighting Regulators

_{of each of these devices is contained in previous} training manuals.

Table 1-2.\Roadway Illumination and Lamp Selection Guide

STREETLIGHTING

Streetlighting at naval facilities usually need not produce as high a level of illumination as that required in many municipal areas. Because night activity by vehicles and pedestrians is low, only enough light is supplied to permit personnel to identify streets and buildings and to furnish sufficient visibility for local security requirements. The streetlighting equipment used need not be as attractive as that frequently installed in municipal systems. It should be functional and of good quality. These factors permit economical streetlighting installations.

STREET AND AREA CLASSIFICATION

Streetlighting requirements generally consist of a minimum average maintained footcandle level and a maximum allowable uniformity ratio for the installation. The authority for these requirements is the American National Standards Institute (ANSI)/Illumination Engineering Society (IES) publication, Standard Practice for Roadway Lighting. Another publication which may prove helpful is Informational Guide for Roadway Lighting, published by the American Association of State Highway and Transportation Officials. The only significant difference between the two publications is that the latter allows a 4 to 1 uniformity ratio instead of the 3 to 1 uniformity ratio specified by IES. These uniformity ratios are defined as the ratio of the average footcandle value divided by the minimum footcandle value.

LIGHTING INTENSITY

The illumination and uniformity requirements are given in table 1-2. Note that the illumination level is dependent upon the roadway classification and the area classification, which are defined in the following material.

Streets are classified into three major categories: major, collector, and local.

Major: The part of the roadway system that serves as the principal network for through traffic flow. The routes connect areas of principal traffic generation and important rural highways entering the city.

Collector: The distributor and collector roadwag traffic between major and local roadways. These are roadways used mainly for traffic movements within residential, commercial, and industrial areas.

Local: Roadways used primarily for direct access to residential, commercial, industrial, or other abutting property. They do not include roadways carrying through traffic.

The locality or area is also defined by three major categories: commercial, intermediate, and residential.

Commercial: That portion of a municipality in a business development where ordinarily there are large numbers of pedestrians and a heavy demand for parking space during periods of peak traffic or a sustained high pedestrian volume and a continuously heavy demand for off-street parking during business hours.

Intermediate: That portion of a municipality ide of a downtown area but which is outs

generally within the zone of influence of a business or industrial development, characterized often by a moderately heavy nighttime pedestrian traffic and a somewhat lower parking turnover than is found in a commercial area. This definition includes military installations, hospitals, and neighborhood recreational centers.

Residential: A residential development, or a mixture of residential and commercial establishments,- characterized by few pedestrians and a lower parking demand or turnover at night. This definition includes areas with single family homes and apartments.