Enginerve : Bikes

10% luck, 20% skill, 15% concentrated power of will, 5% pleasure, 50% pain…a 100% reason to remember the name

How a blue light can keep cyclists from seeing red



From OregonLive

Q: At the intersection of Northeast Sandy Boulevard, 57th Avenue and Alameda Street, the eastbound traffic signal has a little bright blue light just to the right of the red light. Just what is the purpose, function of the blue light?

A: As if that six-way interchange weren’t chaotic enough, the Portland Bureau of Transportation has indeed installed a freaky, brilliant blue LED that appears to be the Eye of Sauron’s little brother.

Stay cool. It’s not watching you. It’s not the ghost of a Kmart special. It’s not revving up to hit you with a proton blast. It comes in peace with a mission to keep bicyclists from getting impatient and running red lights.

You see, when bicyclists approach a red light at a busy intersection, they often fail to position themselves where underground magnetic signal-detection loops can sense their bikes’ metal. When the signal ignores them and refuses to turn green, the bike riders understandably feel they have no choice but to blow the red.

Enter the little blue light mounted next to the red light. It’s attached to the wire coming from the induction loop. When the LED shines, bicyclists know they’re in the sweet spot for detection and a green is on the way.

In fact, over the past two years, the city has installed “detector confirmation lights” at five intersections in Northeast and Southeast Portland. A sixth is planned at Southwest Moody Avenue and Sheridan Street along the South Waterfront.

“These are experimental in nature, and we’re discussing these as a potential new device,” said Peter Koonce, PBOT’s signal, street lighting and intelligent traffic systems manager.

That discussion will happen this summer before the National Committee of the Uniform Traffic Control Devices, where Portland’s trials with intelligent transportation systems are often highlighted. The committee may eventually endorse the technology to be used around the country.

Before people start grumbling about the city spending more money on bicycles when there are potholes to be patched, I should mention that these devices are only $125 each. That’s a steal in the big-budget world of modern traffic-control devices. (It usually costs taxpayers more than $250,000 to purchase and install a new traffic signal.)

Also, if you’re going to complain about the city spending money on these gadgets, you have no right to rant about cyclists ignoring red lights. The LEDs also help motorcyclists, who also have difficulty triggering signals.

Portland is also experimenting with painting bicycle symbols over a neon green background on the pavement above signal loops.

But paint is apparently more expensive than LEDs in the long run. “Our cost estimate of striping markings for detectors is a bit higher,” Koonce said, “and the maintenance is higher because they wear out.”