City Manager Letter

In response to Awaiting Report Item Number 09-72, regarding a report on whether City streetlights are configured to prevent "disability glare", City Electrician George Fernandes reports the following:

Disability glare is an abundance of light greater than the eye can handle resulting in difficulty in seeing objects clearly. This can vary depending on one's eyesight some people can accept more light than others. Glare can be improved by the use of lighting fixtures that reduce or prevent glare.

Street lighting in Cambridge is comprised of a variety of luminaries or fixtures such as full cut-off, acorn, tear drop, shoe box and other pedestrian scale fixtures where most are designed to cut-off light and reduce glare. There are acorn and tear drop fixtures such as those that were installed on Cambridge Street several years ago which is cut-off,  by design of the refractors and positioning of the lamp, shoe box which is square or rectangular and has a flat lens, and other pedestrian scale fixtures which cut-off light according to design as well.

The fixtures most prevalent in Cambridge used on major roadways and residential streets are full cut-off type roadway lighting where the fixture has a flat lens and the lamp is situated in a horizontal position thus keeping lighting at or below the horizontal plane of the fixture which is best suited to eliminate or reduce glare and urban sky glow.

Where there are existing fixtures that are still fitted with non cut-off designs they are changed to a cut-off fixtures as they require replacing, there are approximately 380 non cut-off fixtures remaining out of 7594 total fixtures and are primarily in Harvard and Porter Squares and some along Mass Avenue north of Harvard Square.

Therefore the street lighting in Cambridge is 95% cut-off and designed to reduce glare and urban sky glow.