A street light, is a lighting source on the edge of a roadway, walkway, street and other public area, which will be turned on during night and off at dawn. Some modern street lights also have light-sensitive photocells to turn the lights on at dusk, off at dawn. Street light usually have high pole to distribute lighting to large area.
A street light consists of 5 parts: lighting fixture, pole, arm, flange, embedded parts, power supply.
History[edit | edit source]
The earliest street lights were used by Greek and Roman civilizations, where light primarily served the purpose of security, both to protect the wanderer from tripping over something on the path as well as keeping the potential robbers at bay. At that time, all street lamps use oil to provide lights which is inconvenient and expensive, people need to light it at night and extinguish in the morning. So only noble and slaveholders can use it.
In 1807, A German businessman Frederick Albert Winsor installed the first gas street lights in London to light up garden wall fro the King of England's Birthday. Gas production and gas street lighting spreads rapidly across the industrialised world.
The first electric street lighting employed arc lamps, initially the 'Electric candle', 'Jablotchkoff candle' or 'Yablochkov candle' developed by the Russian Pavel Yablochkov in 1875. This was a carbon arc lamp employing alternating current, which ensured that both electrodes were consumed at equal rates. Yablochkov candles were first used to light the Grands Magasins du Louvre, Paris where 80 were deployed—improvement which was one of the reasons why Paris earned its "City of Lights" nickname. Another resource saying that the first electric street lights was installed on La Rue Impériale in Lyons, France.
New technologies make street lighting more safe and cost effective. LED provides high levels of scotopic lumens allowing street lights with lower energy consumption. Aluminum poles have good corrosion resistance and easier to install.
Type[edit | edit source]
By Pole Height[edit | edit source]
- High Pole Street Lights (higher than 15 meters)
- Medium Height Street Lights (12-15 meters)
- Roadway Lights (6-12 meters)
- Garden Lights (2.5-5 meters)
- Lawn Lights (Less that 2 meters)
By Lighting Source[edit | edit source]
- HPS(High Pressure Sodium) Street Lights
- LED Street Lights
- Energy-saving Street Lights
- Xenon Street Lights
By Power Supply[edit | edit source]
- Centrally Operated On-Grid Street Lights
- Solar Street Lights
- Wind Solar hybrid Street Lights
Advantages[edit | edit source]
Major advantages of street lighting includes: prevention of accidents and increase in safety. Studies have shown that darkness results in a large number of crashes and fatalities, especially those involving pedestrians; pedestrian fatalities are 3 to 6.75 times more likely in the dark than in daylight. Street lighting has been found to reduce pedestrian crashes by approximately 50%. Furthermore, lighted intersections and highway interchanges tend to have fewer crashes than unlighted intersections and interchanges. Towns, cities, and villages use the unique locations provided by lampposts to hang decorative or commemorative banners. Many communities in the U.S. use lampposts as a tool for fund raising via lamppost banner sponsorship programs first designed by a U.S. based lamppost banner manufacturer.
Disadvantages[edit | edit source]
Dangers[edit | edit source]
There are two optical phenomena that need to be recognized in street light installations. The loss of night vision because of the accommodation reflex of drivers' eyes is the greatest danger. As drivers emerge from an unlighted area into a pool of light from a street light their pupils quickly constrict to adjust to the brighter light, but as they leave the pool of light the dilation of their pupils to adjust to the dimmer light is much slower, so they are driving with impaired vision. As a person gets older the eye's recovery speed gets slower, so driving time and distance under impaired vision increases. Oncoming headlights are more visible against a black background than a grey one. The contrast creates greater awareness of the oncoming vehicle. Stray voltage is also a concern in many cities. Stray voltage can accidentally electrify lampposts and has the potential to injure or kill anyone who comes into contact with the post. Some cities have employed the Electrified Cover Safeguard(TM) technology which sounds an alarm and flashes a light, to warn the public, when a lampost becomes dangerously electrified. There are also physical dangers. Street light stanchions (lampposts) pose a collision risk to motorists and pedestrians, particularly those affected by poor eyesight or under the influence of alcohol. This can be reduced by designing them to break away when hit (frangible or collapsible supports), protecting them by guardrails, or marking the lower portions to increase their visibility. High winds or accumulated metal fatigue also occasionally topple street lights.
Light pollution[edit | edit source]
In urban areas light pollution can hide the stars and interfere with astronomy and the migration of many bird species. In settings near astronomical telescopes and observatories, low pressure sodium lamps may be used. These lamps are advantageous over other lamps such as mercury and metal halide lamps because low pressure sodium lamps emit lower intensity, monochromatic light. Observatories can filter the sodium wavelength out of their observations and virtually eliminate the interference from nearby urban lighting. Full cutoff streetlights also reduce light pollution by reducing the amount of light that is directed at the sky which also improves the luminous efficiency of the light.
Green Street Lighting Program[edit | edit source]
As the power consumption of street lights was really high as the street lights need to light up large area and keep lighting for all night long. Take Los Angeles for example. the City's 141,089 street lights consumed 168 gigawatt hours of electricity at an annual cost of $15 million, while emitting 110,000 metric tons of carbon dioxide. Thank to the development of LED technology, the newly designed LED lights could reduce energy consumption by 2/3 to produce the same lighting as the traditional lights. So many cities all over USA are planning for switching to LED to reduce energy consumption.
Green Street Lighting Program in LA[edit | edit source]
Los Angeles started their Green Street Lighting Program in 2008, much earlier than many other cities. And the city has finished replacing the street lights with LED in 2008, this will reduce energy use by 63.1 percent and reduce carbon emissions by 47,583 metric tons a year.
Sustainable Street Lighting for NYC[edit | edit source]
NYC began utilizing electric street lights in the early 1900s. Although many of the historical fixture designs for street and pedestrian lighting are no longer available, several designs remain in use today. The standard luminaires used by NYCDOT currently are the 100W and 150W high pressure sodium (HPS) cobra head for street lighting and 100W and 70W HPS for pedestrian lighting including park lights.
LED lighting is increasingly emerging as a way to capture energy efficiency savings around the world. LEDs provide a crisp white light that enables people to see more clearly at night under lower light intensity than that provided by HPS luminaires. Additionally, the quality of light from LED luminaires depreciates more slowly than light from HPS luminaires. LEDs have a lifespan of 50,000-70,000 hours, which is 2 to 3 times longer than HPS.
San Diego Green Street Lights[edit | edit source]
More than 35,000 low-energy light fixtures are going up across San Diego as the city seeks to cut costs and reduce energy consumption, city officials announced Monday.
San Diego is changing out streetlights with high-efficiency models such as this one to save energy and money. When the project is done in about 18 months, San Diego will have replaced about three-quarters of its street lights as part of a $16 million program. City officials figure it will take less than six years to make their money back in lower energy bills.
City of Redlands Street Light Upgrade Program[edit | edit source]
Systematic, city-wide upgrade of street lights from HPS to LED to achieve the following;
- 1. Superior lighting quality
- 2. Substantial energy reduction
- 3. Substantial reductions in replacement and maintenance costs.
- 4. Reduce the city’s carbon footprint.
Main manufacturers[edit | edit source]
Australia[edit | edit source]
GEC (General Electric)
North America[edit | edit source]
American Electric Lighting (formerly ITT, later Thomas & Betts), USA.
Cooper Lighting division of Cooper Industries, USA.
General Electric, USA.
Osram Sylvania, USA.
LED Roadway Lighting Ltd, Canada
Westinghouse Lighting Corporation (formerly Angelo Brothers) division of the new Westinghouse Electric, USA.
Europe[edit | edit source]
Philips, the Netherlands.
Svetlina AD, Bulgaria.
Thorn Lighting formerly Europhane,United Kingdom
Asia[edit | edit source]
Matsushita Electric Industrial Co., Japan