Traffic Management
The Texas Transportation Institute studies congestion in 85 urban areas around the country. The Institute's studies show that congestion is increasing in large and small urban areas and, as a consequence, more fuel is being wasted. TTI estimated the total amount of fuel wasted in 2002 to be 5.7 billion gallons — about 75 gallons per traveler.
The following technologies are currently available for more efficient traffic management.
LED Traffic Lights
Light emitting diode, or LED, traffic lights are an energy-efficient alternative to commonly used halogen bulbs. But where halogen lights use one large bulb, LED traffic lights are composed of hundreds of LEDs — each about the size of a pencil eraser- placed together in a large array. From a distance, the LED arrays appear as a single, continuous light source. LEDs have three main advantages over other bulbs:
LEDs are brighter.
LEDs last longer. Replacing bulbs requires money for trucks and staff time, and ties up traffic.
LEDs are considerably more energy efficient than conventional bulbs. The energy savings of LED lights can be huge: LED bulbs consume 15 or 20 watts; many of today's bulbs use 100 watts.
Energy efficiency results in huge dollar savings. For example, if a traffic light uses 100-watt bulbs today, and the light is on 24 hours a day, it uses 2.4 kilowatt-hours per day. If power costs at $0.08 per kilowatt-hour, one traffic signal costs about $0.20 per day to operate, or about $73 per year. There are perhaps eight signals per intersection, so that's almost $600 per year in power per intersection. A big city has thousands of intersections, so it can cost millions of dollars just to power all the traffic lights. LED bulbs might consume 15 or 20 watts instead of 100, so the power consumption drops by a factor of five or six.
Consequently, a city can easily save a million dollars a year by replacing all of the bulbs with LED units. These low-energy bulbs also present the possibility of using solar panels instead of running an electrical line. This can save money in urban and remote areas.
Additionally, individual LED lamps can display multiple colors and patterns. Individual LEDs can be turned on or off, and LEDs of different colors can be mixed in the same lamp.
Synchronized Traffic Lights
Traffic lights that are not synchronized result in excessive engine idle time at red lights. This results in reduced fuel efficiency, increased automotive emissions, and reduced worker productivity because of longer commuting times. Synchronized traffic lights can help reduce driving time and vehicle emissions and increase fuel economy.
There are various control systems for traffic lights. The simplest controls use a timer where each signal last for a certain amount of time, regardless of traffic. More sophisticated controls use underground electronic sensor loops that detect waiting traffic. Sensor loops operate like small metal detectors, so they often fail to detect motorcycles, bicycles, or vehicles with low metal content. Usually timers are installed as a backup.
Traffic light synchronization technology is becoming more sophisticated. Traffic lights are sometimes centrally controlled by monitors or by computers to allow them to be coordinated to deal with changing traffic patterns. Sensors can be used to monitor traffic patterns across a city. Unsynchronized sensors occasionally impede traffic by detecting a lull and turning red just as cars arrive from the previous light. To prevent this, the most high-end systems use dozens of sensors and are costly, but can very finely control traffic levels. This relieves the need for other measures (like new roads) which are even more expensive.
In some areas, traffic lights may also be turned off when traffic is light. Under these circumstances, traffic in the main street may get a flashing amber to warn of an intersection. Traffic in the secondary streets get a flashing red, or sometimes the lights are marked as operating at set times only. In many parts of Europe, traffic light-controlled intersections also have yield and right-of way signs in case the signals fail or are turned off.