Dear Mr. Tangherlini:
Prior to their meeting of 18 November, the Commission inspected the proposed new prismatic globes on the Washington street lights lining the three blocks of 9th Street north of Pennsylvania Avenue. All the globes and lamp fixtures in this demonstration installation were thought to be less than ideal, especially the ones north and south of E Street. These globes and internal fixtures produced an effect in which the tops and bottoms of the globes were not illuminated and the light emanating from the fixtures was harsh to the eye with the pattern of the prismatic plastic being a distracting feature. The globes on the lights just north of Pennsylvania Avenue were only marginally better in that the tops and bottoms of the globes were illuminated. Overall the members felt that all of the globes in the demonstration were unacceptable.
Perhaps another strategy should be investigated where the light controlling lens is not part of the outer globe, but an inner layer between the globe and bulb. This configuration is similar to that of a traditional lighthouse in which the central light source is surrounded by a light-controlling Fresnel lens, which in turn is enclosed and protected from the elements by the windows of the lighthouse lantern. This model could be, at a much smaller scale, adapted to the streetlights to produce a fixture that is efficient and visually pleasing.
The Commission looks forward to further review of the District Department of Transportation’s efforts to improve street lighting and of new prototypes for the city’s streetlights and fixtures. As always, the staff is available should you require assistance.
/s/Frederick J. Lindstrom
Mr. Dan Tangherlini
District Department of Transportation
2000 14th Street, NW, 7th Floor
Washington, DC 20009
cc: John Dietrick, DDoT
Colleen Hawkinson, DDoT