A light unto my interstate


Much talk this week about the decision by the City of Tulsa to save money by turning off lights along the expressways. The Whirled expressed its embarassment on the editorial page. Charles Hardt, director of the City's Public Works department was on KFAQ explaining that lights aren't critical to safety on limited access highways where there there are no pedestrians and few interchanges. Michael DelGiorno held a two-day "radiothon" to raise the $12,500 needed to turn the lights back on for one month.

I drove a bit of unlit I-244 last night and it wasn't bad, but it helped that there were other cars to follow, and the lines on the road and embedded reflectors were easily visible. I-44 east of the 244 junction is still lit from above, but I notice that the lane lines are dim and the reflectors are barely peeking above the asphalt. Such a road would be dangerous without overhead lighting, especially in foul weather. In my travels, I've noticed that Texas is far more diligent than Oklahoma about maintaining the reflectivity of their road markings.

I also noticed that turning off the lights along 244 meant that the lights were out on the Yale Avenue overpass, where you have sidewalks, the occasional pedestrian, and traffic intersections. That didn't make much sense.

I agree that it's pathetic that we can't find the money to keep the lights on. It looks bad for our city. It reinforces the need to investigate how we're spending tax dollars so we can spend money on what really matters. But I also believe that most of the lights along the expressways can be safely switched off, improving visibility in the process.

A few years ago I first met Patric Johnstone, a Tulsan who has been researching this issue for several years. The heart of his message: Everything you think you know about outdoor lighting is wrong. More is not necessarily better. Far from promoting safety and security, badly designed lighting can actually make matters worse, sending glare into the eyes of drivers (one reason why many older folks hate driving at night), creating deep shadows, and encouraging neighbors to keep blinds and shutters closed (making life safer for those up to no good).

Patric submitted a proposal to the Mayor's Competition for Better Government and was one of the finalists. Johnstone points out that the city's outdoor lighting is wasteful -- sending more light up into the clouds or into the eyes of drivers rather than directing it all toward the ground where it does some good. Increasingly, cities and businesses are going to full-cutoff lighting -- the light source is recessed inside a reflective fixture, providing better lighting on the ground for lower cost, because all the light goes where it's supposed to go. I notice that new businesses are installing full-cutoff lighting, not because they're required to, but because it reduces their cost. (See the Lowe's at 15th & Yale as an example. An apartment building at 13th & Elgin uses wall-mounted full-cutoff lights to provide good lighting at ground level without blinding the residents indoors or the neighbors.)

Patric has endorsed switching off most of the lights along the expressways, while leaving ramps, overpasses, and intersections lit. This is the standard practice outside metropolitan areas. From a letter he's submitted to the Tulsa Whirled:

When the Texas Department of Transportation began replacing lights on highways and signs with highly reflective microprismatic markings ("passive" illumination), their utility bills began to plunge. The doom-and-gloom predictions of decreased safety never materialized, as fewer drivers were tempted to speed beyond their headlights (as they often do with continuously-lighted highways.) Texas was also the first state in the region to require new streetlighting only be used when the task couldn’t be accomplished by more economical means.

National highway safety studies have found no real benefits to motorists
with continuous streetlighting, so this is one false sense of security
we can safely discard now that we can no longer afford it.

Here's a link to some examples of good and bad lighting. And here's a link to more.

Patric is also concerned about the fad of using "acorn" lights to lend authenticity to historic areas. Acorn lights are designed to look like gas streetlights of long ago, but the lamp is a modern sodium light with a bright pink glare. I was once driving through a small town in southwestern Oklahoma (Fletcher, I think it was), and there were acorn lamps at 20 foot intervals all along the main street, making it impossible to get a good look at the historic buildings allegedly enhanced by the lighting. There are full-cutoff lights designed with a historic appearance, and they don't cost any more than the bad lights.

Now that budgets are tight, it's a good time to realize that well-designed lighting costs no more than bad lighting to install, and is far cheaper to operate and maintain as it does a better job of providing for safety, security, and comfort.

UPDATE: Here are some more photos illustrating good and bad outdoor lighting practices. Here are some examples from New York state. And here are some more, with an explanation of how glare impedes visibility:

Since the eye has an effective ability to discern details in a scene if the range in brightness (the contrast) is about 10 to 1 or less, it is important that when driving, important details such as the roadway or parked cars not be masked by bright, glary light bulbs. If unshielded or poorly-aimed lights are in view of drivers, then the lights set the upper brightness range - things 10 times less bright like potholes, trees or pedestrians become featureless. The following are examples where such situations occur. ...

Efficient light fixture design puts all of the light where it is needed: on the road, vehicles, and pedestrians. Shielded, full cutoff and properly aimed lights are generally not part of the driver's view, so the 10:1 brightness range occurs entirely on the ground between cars, trees, pedestrians, etc.

The Illumination Engineering Society of North America (IESNA) is the principal technical body that establishes indoor and outdoor illumination requirements. The IESNA recently revised its current recommended practices for roadway lighting. Its guide ANSI/IESNA RP-8-00 now includes strong recommendations that all streetlights be fully shielded. These modern standards seek to reduce glare for drivers and pedestrians, which improves visibility and, hence, safety. The reduction of glare is far more important to visibility than the absolute illumination level. Glare reduction is especially important for older drivers.

And here's an article about one town in Idaho which is improving public and private outdoor lighting.

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This page contains a single entry by Michael Bates published on September 28, 2003 12:41 AM.

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