May 2011 - Illuminating Engineering Society

NEWSMAKER
First Choice in
the Second City
Three letters—CMH, not LED—define
Chicago’s new street lighting strategy.
Spearheading the transition is the city
DOT’s chief engineer, Mohammed Rashed
The conversion to ceramic metal halide
includes residential and arterial streets,
along with alleys.
A
while back, the Chicago Department of Transportation received a heartfelt letter
from a concerned citizen who expressed dismay with the city’s street lighting: “You
know what, I want less streetlights. I know you guys are nice and all, but seriously
do not use so much energy. . . .In conclusion, let’s have a less polluted earth.”
The author of the letter was a child, and today that youngster is getting his wish. The city
of Chicago has committed to reducing its energy usage and carbon dioxide emissions by revamping
its street lighting—specifically by swapping yellow for white. On the way out are
high-pressure sodium streetlights with their yellow light. Taking their place is the white light of
ceramic metal halide, which has become Chicago’s official streetlight source of choice.
That’s right: When it seems every municipality is gravitating to solid-state lighting, the
three letters that spell white light in the Windy City are CMH, not LED. “All new installations
moving forward will have CMH,” says Mohammed Rashed, chief engineer of electrical
operations for the Chicago DOT and a member of the Mayor’s Streetscape Task Force,
who is leading the streetlight conversion effort.
Chicago’s road to CMH began with a “White Light Study,” during which induction, LED
and CMH luminaires were installed on three residential streets and adjacent alleys. A survey
was distributed to area residents for feedback. “Once the survey was completed, it was
evident that the local residents opted for the white light instead of the traditional yellow light
or high-pressure sodium,” says Rashed. “It was also evident that the white light provided
better visibility and color rendering, along with an overall higher quality lighting system. This
was all accomplished despite the lower wattage of the tested luminaires.”
At the same time as the White Light Study, Chicago DOT was conducting research on induction,
LEDs and CMH. Rashed explains the findings: “While induction lighting is not new, it
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