Last Updated: August 8, 2020
Residents and business persons often advocate for and are involved in the selection of street lighting. This page provides enough background information and explanation of the jargon to help you make good decisions.
The root purpose of street lighting is to assist drivers, pedestrians, and cyclists in finding their way in the dark. Many neighborhood groups believe that extra illumination helps prevent crime, and business district lighting also may help create a mood or a pleasant environment.
One of the first questions to clarify is whether your goal is to light the street or pedestrian ways. This will determine the height at which the lights will be mounted and also may influence your choice of lights.
Street lighting is not actually aimed at showing the way directly ahead of the automobile; the car lights do that. But it does illuminate adjoining areas to alert drivers to the emergence of possible hazards from the side.
Pole height is extremely important in the way that light is distributed, so transportation engineers typically want to mount the lights higher on higher-speed roads.
To be safe for drivers, light needs to be relatively constant. We know our eyes adjust faster to going out into the sun than to walking into darkness. For awhile when we enter a dark room, our vision is impaired. Therefore, driving from a well-lit area to a dark one produces a similar effect. So ideally if an area must be illuminated, the globes are mounted on high poles fairly close together so that the light stays constant, and the eyes are not continuously readjusting for different levels of brightness.
For pedestrians, the goal usually is illuminating the walkway itself. Extra dark spots along sidewalks can be created by a variety of conditions, including trees, rows of large shrubbery, odd angles of the streets, parking patterns, a tall building or church steeple, or a host of other potential influences. Pedestrian-oriented lighting should be installed on a lower pole than automobile-oriented lights, although pole sharing is common too.
Keep in mind too that as the popularity of bicycling swings upward, you'll need to monitor the impact of the presence or absence of lighting on those new bike lanes and trails.
Just as you now face an array of choices for your household light bulb, so too there are several choices for street lighting. LED lighting is becoming the obvious choice as cities replace or add lighting, due to their superior energy efficiency and also the bright light that often pleases residents. This way of thinking will predominate among cost-conscious engineers and city officials.
However, you will still find many other types of fixtures in use now, including the older mercury vapor, sodium vapor or high pressure sodium, and metal halide lamps. Some historic districts and areas of nice older homes simply find the daytime appearance of the LED lamps too boxy and high tech, and may also prefer a softer but less bright light at night.
LED lights are so-called white lights, causing their bright appearance that is familiar to you because of vehicle headlights. LED lights also emit a smaller quantity of so-called blue light, causing them to be somewhat controversial with folks who worry about sleep disruptions for humans and animals due to blue light. Metal halide lamps make colors look more natural, and thus are often particularly preferred in business districts. High pressure sodium casts the eerie yellowish glow that some historic business districts have come to love. Some designers prefer one color effect over another, just as at home you choose between bright white and soft white depending on the mood of the room.
In addition to the color quality and quantity of light produced, the initial cost of the unit, energy cost of operation, and maintenance requirements also will factor into the decision that your subdivision, city, or other local government ultimately makes.
We have purposely omitted any discussion of solar lighting up until this point. Solar street lights can range from the traditional tall "cobra head" lights you see on highway exits to shorter, decorative pole lighting more typical of business districts. Often a solar installation uses an LED bulb, following through with the theme of energy efficiency. No doubt you have seen a street lamp with a small solar panel attached. Obviously it would be great not to have an electricity bill, but you have to weigh this against questions about the likely life of the batteries and solar photovoltaic panels, and the amount of energy that the battery can store. Especially in situations where new wiring would be required, solar applications have much to offer.
Often in areas that seem more crime-prone, people will demand more and more lighting. In fact, uniformity is much more important than brightness for crime prevention. A high light level can cause glare, whereas a consistent but lesser amount of light increases perception of safety.
The distribution of light on the surface of buildings can increase perception of safety in business districts. Research isn't definitive on whether very high levels of street lighting actually deter crime; one can find results to support either argument. One school of thought, CPTED (Crime Prevention Through Environmental Design), does emphasize good lighting that does not create shadows as one of several central tenets. Nevertheless, many community groups are convinced that lighting is part of their crime-fighting arsenal, and if that sentiment is strong enough, often utilities and local governments give in.
Street lighting is often chosen for aesthetic reasons in a business district, and sometimes in residential areas as well. To complement the appearance of an historic district, for example, period fixtures may be selected. New lamps often are an important feature in a commercial district revitalization project.
We typically caution business districts to think twice before deciding to return to a history they never had. Certainly modern extensions of an existing historic district would want the same lighting as the adjacent genuinely historical area, but brand new faux colonial buildings may not need brand new faux colonial lighting, especially if the cost exceeds an otherwise effective choice.
Projects may remove all existing lighting and start over, or piecemeal improvements may be proposed and debated, often with the goal of saving money. In business districts, your town might decide to add new period lights for the pedestrian and maintain the older and higher lights for the driver. The period lights may even serve more as a daytime decoration than as a serious source of light for nighttime. Sometimes this is a compromise reached between engineers and appearance-oriented business improvement districts.
The typical older fixture, which you might hear called the "cobra head," is 30 or 35 feet high. and designed for drivers rather than pedestrians. I think retaining these old cobra heads detracts somewhat from the appearance of a new streetscape, but you may have to satisfy the traffic engineers with this compromise.
If you decide to add new lighting, poles and lamps each may be quite decorative, or modern and minimalist in their design. Boxy lights are common at discount store parking lots, but elaborate 19th century looks are typical of older business districts. For decorative and pedestrian-oriented installations, work with a representative affiliated with several companies for the best choice. The manufacturer will supply suggested heights and spacing, as well as other types of specifications, although your local engineer may choose to modify some suggestions.
Most districts need to consider future uses of their light poles as well. Many cities already use sensors mounted on light poles to regulate traffic signals, decrease the amount of LED lighting to be emitted at certain times of the day, turn on the lights only when a car or pedestrian appears, sense gunfire, or hold the boxes for small cell technology that enables advanced broadband. Others are preparing for the world of autonomous vehicles when quite an array of signals to and from the vehicles themselves will need to be consolidated. We mention all of this to help you realize that aesthetics and economy are not the only considerations in pole selection.
If you have the financing, or can require developers to provide the financing, for underground burial of the wiring, the aesthetics are much better than above-ground wires. In fact, whether or not new fixtures are purchased, communities sometimes choose the expensive process of burying the wiring, believing it will be a valuable turning point in improving the aesthetics of a shopping district. Reluctantly we have come to the conclusion that the benefits often do not outweigh the costs.
Lastly, after you basic look is set, you may want to choose some accent lighting for landmarks, monuments, fountains, gardens, or particularly striking buildings.
We think street lighting should be required as new subdivisions and residential districts are developed, and that the wiring should be required to be buried underground. We are being consistent with our theory that a walkable or bikeable community is highly desirable.
In existing residential areas, the preference of the residents is often the most important factor. Some neighborhoods feel safe and semi-rural, and illumination would only serve to annoy residents unless it is imperative for driver safety.
Even then, specific drop-offs or other roadside hazards might better be highlighted through use of simple reflectors rather than an elaborate street lighting program. In many locations, residential street lighting is added and bulbs are replaced only when residents complain.
Often you can pay for the installation through a special assessment, a voluntarily assumed tax on a defined group of residents and/or businesses. The special assessment would be in effect for a specified number of years, and typically paid off monthly as part of the utility bill.
Of course a special assessment that is paid monthly or annually "runs with the property," meaning that if a house is sold, the next owner is liable also. Special assessments on a one-time-only basis also are legal in some states and situations.
For residential streets, the recommended interval between fixtures is often every 400-600 feet, but it's more practical to take local climate and tree cover into account before determining this. The color and reflectivity of the street surface also matter.
Decision-making, and therefore conflict, about what to do when the distance isn't easily divisible by the recommended interval is common too. So be prepared for some lively conversations with citizens.
These discussions often become contentious in areas of the urban fringe where some people regard themselves as rural and want no part of street lights, while others want to enjoy the same safety advantages as their city cousins when it comes to lighting. Here we are afraid we cannot offer any guidance except to say that this decision should revolve around an open and thoughtful community dialogue.
Electric utilities, which sometimes are municipally owned, typically play a major role in street lighting in communities. The utility may even offer you a menu of choices and tell you these are all the lights that are available to you.
Of course, other options usually can be made acceptable, but be prepared to pay the price, both economic and in terms of time and effort required to persuade the utility to change its ways.
If you need or want replacement street lighting, it's also worth asking the utility to share in this cost. Many utilities will have a favorable policy if the older lights are more than a certain age.
Why should you ask for new street lighting? A newer street light will probably be more energy-efficient. Also dilapidated or leaning poles or fixtures detract from the appearance of a neighborhood, even during the daytime.
It's also common in some parts of the country for municipalities, homeowners associations, or other entities paying for street lighting to be able to lease rather than buy the fixtures from the utility. If you lease, you're almost certainly going to be limited to the utility's selection.
Sometimes municipalities will maintain their own street lighting, and sometimes that burden is assumed by the utility. And it's possible the utility will offer choice too. In some parts of the country private companies sell the service of maintaining the street lighting, including bulb replacement.
Light pollution (unwanted light in the sky in general) and light trespass (unwanted light that shines on adjacent properties) also are increasingly important concerns. Someone is bound to say they want a dark sky, while others will think that is ridiculous.
If light trespass bothers residents, expect complaints. In the last 25 years or so, great progress has been made in providing highly directed street lighting that does not spill over onto unwanted areas.
If you need to retrofit older street lights to solve problems of lights shining into bedroom windows, directional shields are available at a much lower cost than replacing an entire fixture or street of fixtures.
Some towns and cities have so-called dark sky ordinances,
requiring street lighting to be highly directed, not spilling over into
the sky. Manufacturers also are rising to the occasional by producing night sky fixtures.
In terms of operational cost, there are additional
considerations beyond simply the electric bill. These include how frequently bulbs have to be replaced, what
happens when a car hits a pole, whether poles or lamps will have to be painted or cleaned to maintain appearance and functioning, and the projected life of the entire
If maintenance requires special equipment that your neighborhood or town does not have access to, any costs for necessary equipment must be factored in. These may not be insignificant.
The steps in your illumination program, then, would commonly occur in this order: