The New Yorker on city lights

[patric]

The article is mostly about ecotourism, yet an interesting read that might illuminate some thinking on how we light our city at night.

The New Yorker magazine
Much so-called security lighting is
designed with little thought for how
eyes—or criminals—operate. Marcus
Felson, a professor at the School of
Criminal Justice at Rutgers University,
has concluded that lighting is effective
in preventing crime mainly if it enables
people to notice criminal activity as it's
taking place, and if it doesn't help criminals
to see what they're doing. Bright,
unshielded floodlights — one of the
most common types of outdoor security
lighting in the country — often fail on
both counts, as do all-night lights installed
on isolated structures or on parts
of buildings that can't be observed by
passersby (such as back doors). A burglar
who is forced to use a flashlight, or
whose movement triggers a security
light controlled by an infrared motion
sensor, is much more likely to be spotted
than one whose presence is masked
by the blinding glare of a poorly placed
metal halide "wall pack." In the early
seventies, the public-school system in
San Antonio, Texas, began leaving
many of its school buildings, parking
lots, and other property dark at night
and found that the no-lights policy not
only reduced energy costs but also dramatically
cut vandalism.

The mall's large parking lot was fully
illuminated—as we walked from the car
to the restaurant, I had no trouble reading
notes that I had scribbled in my
notebook—but it was free of what dark-
sky advocates call "glare bombs": fixtures
that cast much of their light sideways,
into the eyes of passersby, or upward,
into the sky. Tucson's code limits the
brightness of exterior fixtures and requires
most of them to be of a type usually
known as "full cutoff" or "fully
shielded," meaning that they cast no
light above the horizontal plane and
employ a light source that cannot be
seen by someone standing to the side.
These are not necessarily more difficult
or expensive to manufacture than traditional
lights, and they typically cost less
to operate. Calgary, Alberta, recently
cut its electricity expenditures by more
than two million dollars a year, by
switching to full-cutoff, reduced-wattage
street lights.
Diminishing the level of nighttime
lighting can actually increase visibility. In
recent years, the California Department
of Transportation has greatly reduced its
use of continuous lighting on its highways,
and has increased its use of
reflectors and other passive guides, which
concentrate luminance where drivers
need it rather than dispersing it over
broad areas. (Passive guides also save
money, since they don't require electricity.)
F.A.A.-regulated airport runways,
though they don't use reflectors, are lit in
a somewhat similar fashion, with rows of
guidance lights rather than with high-powered
floodlights covering broad expanses
of macadam. This actually makes
the runways easier for pilots to pick out
at night, because the key to visibility, on
runways as well as on roads, is contrast.

After dinner, Crawford showed me
his home, in a subdivision of small,
closely spaced, desert-colored stucco
town houses. Tucson gives individual
neighborhoods the right to choose
whether they want street lights (and to
pay for them if they do). Most of the
newer, more afluent residential areas,
and a number of commercial blocks,
have elected to do without. Crawford's
subdivision, to his annoyance, does have
street lights, and the fixtures, though
technically shielded, have frosted-glass
side panels, which diffuse the light in a
way that turns them into glare bombs.
Crawford pointed out a cluster of mailboxes
across the street from his garage.
The lighting near the mailboxes was of
a type that Crawford calls "criminal friendly":
it was almost painful to look
at, and it turned the walkway behind the
boxes into an impenetrable void. "The
eye adapts to the brightest thing in
sight," he said. "When you have glare,
the eye adapts to the glare, but then you
can't see anything darker."