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Traffic Signal Innovations

With the increasing demands of reliability and efficiency on the SDOT Signal system, the SDOT Signal Shop has started to experiment with new construction procedures and equipment that can make our system more robust and resilient.

We’ve begun using steel mast arm signal poles which can double the life expectancy of our signal equipment as well as decrease the amount of maintenance calls for things like wind storms.  They are also much more visually appealing than a span wire system.


Have you noticed? New steel mast arm signal poles replaced the old signal poles at 2nd and University Street.

signal construction

How’d they do that? Vactor excavation.

In the downtown core, it can often be very difficult to install foundations for these new poles because there are many utilities running underneath the pavement.  One of the different construction procedures we have started using is vactor excavation which uses high pressure water to loosen the dirt and a vacuum to remove the debris instead of digging with a large auger bit.  Not only does this style of construction avoid damage to underground utilities but it is actually cheaper to perform because it only takes a few hours to dig even a 10’ deep hole.

We’ve also started updating our communication systems from copper to fiber and connecting signals that are currently not part of the system.  Fiber communication allows us to use our central systems to talk directly to devices in a redundant network rather than point to point.  This means that if one part of the system goes down it doesn’t take the whole network down.  Imagine this like going from the old incandescent Christmas lights to new LEDs.

Moving forward, we have started exploring new technologies like infrared and thermal pedestrian detection, real-time data collection, wireless communications between signals, solar power and materials with a smaller footprint to assist with more pedestrian and bike friendly urban designs.

If you have questions, you can contact Brian Forsythe at or at 206-386-1538.

For more information about SDOT’s Traffic Signal Program, please visit