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sts.components.contact.mr.placeholder Sebastian Webel
Mr. Sebastian Webel

Editor-in-Chief

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Pictures of the Future
The Magazine for Research and Innovation
 

Urban Mobility

World’s Thriftiest Traffic Light

The old-fashioned traffic light is experiencing a rebirth – and thanks to Siemens it will be extremely energy efficient.

A new LED technology from Siemens guides traffic while consuming up to 98 percent less power than traditional incandescent systems.

Siemens Engineers have managed to reduce the average power consumption of a traffic signal – red, yellow, green – to just one to two watts. For traffic lights based on incandescent bulbs, this value amounts to around 60 watt. The new traffic light, which is based on highly efficient LED and digital modules, is expected to benefit city budgets as well as the environment thanks to the enormous energy savings. To achieve such the new 1-watt-technology – branded as Sitraffic One – is already in use in pilot projects in Bozen, Italy and in Bietigheim-Bissingen, in southern Germany.

Why it’s Worth it

Conventional incandescent bulbs behind colored diffusion disks are still in operation in many traffic lights around the world. Converting these to the new 1-watt technology reduces power consumption by up to 98 percent. Cities can cash in enormously by replacing incandescent bulbs with 1watt-technology. After as little as five years, a converted intersection begins paying for itself. Even updating conventional 230-volt LED technology pays off: at an average intersection with about 55 signal lights, the new 1-watt signals can save about 1,600 kilowatt-hours per year and reduce carbon emissions by about 960 kilograms.

Multi-layered Approach to Safety

Two technological advances are at the heart of the new system. First of all, digital driver modules have replaced the electronic systems that drive the LEDs. This eliminates the need for load resistors and switching elements in the signal light units, which until now have consumed most of the energy. On top of that, the new signals employ modern, highly efficient LEDs that consume considerably less power to deliver the required brightness. Compared to conventional 230-volt LED technology, the 1-watt solution consumes up to 85 percent less power.

Monitoring of the individual signal lights has also been improved. For instance, one primary safety criterion is that traffic lights must never give green signals to crossing traffic at the same time. Today, voltage and current are monitored for each signal light. The signal is considered active if these values reach a certain level. During this period the traffic light control system prohibit switching another signal to green. In addition to this kind of indirect monitoring, the new technology monitors whether the signal lights are actually on – a first. A photo sensor in each module registers the light emitted by the LED. With this multi-layered monitoring concept, the 1-watt traffic light achieves an extremely high level of safety. According to the safety standards for electronic systems, it has been certified with level SIL 3.

Conventional incandescent bulbs behind colored diffusion disks are still in operation in many traffic lights around the world. Converting these to the new 1-watt technology reduces power consumption by up to 98 percent.

The new 1-watt traffic light has also been made more robust against voltage and frequency fluctuations in the power supply. Such fluctuations are caused by feed-in of renewable energy sources and could thus become increasingly frequent, conceivably causing traffic lights to fail in the worst case. With 1-watt technology, a special circuit in the traffic light controller decouples the power supply for signal light units from the grid, resulting in significantly higher device availability. Moreover, by minimizing heat stress on its components, Siemens has further improved the unit’s lifespan, thus considerably reducing maintenance costs.

Christine Rüth
Picture credits: from top: 1. picture imago/Peter Widmann