I noticed the red light on Bay and Jones is out. The reason why is it’s one of the only incandescent traffic lights left in the city. I like to call it my reference light because it reminds me of what traffic lights used to look like: dim and a slightly different shade of green and amber. We’ll not see them anymore.

I remember the excitement when the first LED traffic lights came up. Back then they only replaced the red bulbs because nobody had perfected the p-n junction blue LED. But soon, those were mass produced and soon all lights in the the traffic lights were LEDs. You recognized them because LEDs were so small that the lights were composed of an array of them with little lenses in front of them. Imagine what a change we’ve wrought!

A typical incandescent light lasts just under a year—8000 hours. This means that for every 110 traffic lights in the city, one is in need of replacement every day. Maybe your entire job is to replace street lights alone. An LED run correctly will last between 50,000 and 100,000 hours—almost 10x longer. Imagine that. Add to that the LED light uses between 6-20x less power depending on which generation and that’s probably a huge power savings for the city to boot.

Maybe about a half million dollars a year in labor and power for a medium sized city!

Another thing I miss is the heating time. LEDs turn on instantly, incandescents take a fraction of a second for the filament to heat on and start emitting light. In the early days that was how they tried to convince car companies to replace your red tail light with LEDs because that fraction of a second would make the car safer for rear end collisions. It didn’t work.

Finally they just pointed out that with LEDs you could make taillights in almost any shape and they started to sell like hot cakes.

I’ll miss the old traffic light. But it won’t stop me from e-mailing the city

Time marches forward.