March 10


48 Volt DC Traffic Signal?

By Mike Spack

March 10, 2016

48 Volt DC, COUNTcam, LED lights, solar panel, traffic signal

Traffic Light 2 - NACThere was a post a while ago on the ITE bulletin board wondering if anyone knows of a working 48 volt DC traffic signal system.  None were identified, but Pete Yauch (I believe to be one of the nation’s leading signal engineer who works at Albeck Gerken) likes the idea and pointed out these advantages:

  • Much simpler LED modules in the signal heads
  • Smaller load switch size allows a much smaller cabinet – great for restricted rights of way
  • Reduced load which opens up the opportunity for solar powered signalized intersections at remote locations
  • Reduced load also allows longer battery backup
  • Less of an electrical hazard in a knockdown
  • Exempt some of the installations from NESC requirements, with the possibility of running signal and detection circuits in the same conduit.

Pete also pointed out railroad crossing signals have been battery powered using low voltage circuits for years.

The wires we use in signals are orders of magnitude thicker than they need to be since we’ve switched to LED signal heads.  And now our industry is switching to LED street lights.

The whole signal system, including the controller computer, is long overdue for a complete redesign.  A year and a half ago we redesigned our COUNTcams around 7.4 volt DC lithium ion batteries.  I know LED lights, cameras, and electronic circuit boards can be designed to work with 12 volts.

I would go so far as to propose a battery in each signal pole base with a solar panel on top of each mast arm.  It’s possible the signal heads and detection could all be wireless.

The engineering to design a completely new, low power traffic signal is straightforward and very achievable.  The issue is I’m not sure who would need to get motivated to make this happen?  Maybe this is a function of the Institute of Transportation Engineers.  I don’t think a private company could successfully push against the current government standards.

  • I agree, it make sense to go to the low voltage signal. However, the distances that we are running the signal wire is prohibitive with the small wire we are using. I have looked into this recently, 14AWG and DC does not go very far without significant voltage loss. That is not insurmountable though. Just need someone in the Electrical Engineering field to work on this.

  • I have no doubt this will happen. The first step would to install a AWF with out wires. A simple solar panel and radio activation is all it would take. Once this is installed the rest will happen pretty quickly.

  • One thing to keep in mind when trying to solve the voltage drop problem is that whenever a signal is repeated, unless simple transformers are used, we run the risk of requiring additional MMU/CMUs for monitoring the final display. Not insurmountable, but it could drive up costs to make the process unusable.

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    Mike Spack

    My mission is to help traffic engineers, transportation planners, and other transportation professionals improve our world.

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