Road Worrier: How bikes share the roads and make the lights turn green

bsiceloff@newsobserver.comSeptember 18, 2012 

Two kinds of bicycle symbols have popped up as pavement markings on more and more miles of Triangle streets over the past couple of years. If you don’t have the Road Worrier’s secret decoder ring, you may find their meanings to be mysterious.

These white-paint stencil markings will become increasingly familiar in the future, as transportation engineers step up their efforts to accommodate two-wheel traffic on our streets.

So let’s decipher them now.

There’s an inscrutable symbol designed to help a bicyclist turn red lights into green. It’s so small that an automobilist may never notice it. More about this one later.

First, though, let’s take care of the shared-lane arrow, better known as the sharrow. It’s a bike topped with twin chevrons. Sharrows send out separate messages for cyclists and for motorists.

“They’re a marketing tool to remind drivers that these are places where they should expect to see cyclists in mixed traffic,” said Eric Lamb, transportation planning manager for Raleigh, where sharrows were applied this summer to six miles of bike-busy streets.

And for bike riders, the sharrows offer a suggestion about where to ride on that stretch of the street. Should a cyclist stay in the center of the lane, or move to the right? It depends.

On Clark Avenue in West Raleigh, the new sharrows are painted in the center of the lane along several blocks, where parked cars make the travel space narrow. This section of the street isn’t wide enough for cars and bikes to ride easily side by side.

Then when you hit the no-parking zone on Clark and there’s more room for traffic, the sharrows move closer to the right-hand curb. The city recommends – but does not require, Lamb points out – that slower bikers keep to the right here so faster cars can pass them easily.

Raleigh is not among the North Carolina cities that have installed special pavement sensors for bicycles at traffic-signal intersections. But you can find these bike detectors in Charlotte, Greensboro and Chapel Hill.

Car folks are familiar with loop detectors – the big rectangular loops of electric wire, buried in the asphalt on many a side street to detect cars waiting for the light to turn green. The metal of an arriving car interrupts an electromagnetic field created by the loop.

Bikes are small, with only a few pounds – or ounces, if you ride one of those carbon-fiber babies – of metal. These big loop detectors don’t always work for bike riders. And when cyclists can’t make the light turn green, they’re forced to take a chance and break the law.

“We don’t want ’em running red lights,” said Rob Myers, traffic signals engineer for the town of Chapel Hill. “We promote bicycle safety. We promote bicycles getting out in the road with the rest of the vehicles.”

So Chapel Hill has bike loop detectors – smaller and more sensitive than the car kind – buried in the pavement at more than 40 intersections. Some of these are as much as 7 years old, but most were installed in the past two years with federal stimulus money.

Bike loop detectors sometimes are aligned diagonally across the lane, making it easier for the biker to come in contact with the electromagnetic field. That sweet spot on the pavement is painted with a different kind of bicycle symbol with vertical bars.

The message to cyclists: Put your bike right here to get a green light.

Sometimes bike riders need this help on country roads, too. On days when the weather is nice, you can find scores of cyclists crossing U.S. 64 on Farrington Road in Chatham County.

But for years, they could never get a green light. Cyclists would coax motorists to pull their cars onto the big loop detector.

“Unless a car came up behind you, the light never changed,” said Art McMillan, a DOT engineer who rides on weekends. “So what are you going to do then? Try to dash across 64 in between cars?”

DOT installed a loop detector and painted that funny little cyclist symbol on the pavement a couple of years ago, after McMillan and a group of Cary riders asked for help. Now a cyclist crossing U.S. 64 there has to wait only about 20 seconds for a green light.

We’ll see more sharrows in the future, and more bike loops.

Raleigh is laying plans now for an additional 14 miles of bike lanes and eight more miles of streets with sharrows. And city engineers hope to start a pilot project with bike detectors at a couple of intersections in the coming year, said Jed Niffenegger, a senior transportation engineer for the city.

“If people take their bikes, we don’t want to punish them by making them wait excessively long at a signal,” Niffenegger said.

Make contact: 919-829-4527 or bruce.siceloff@newsobserver.com. On the Web at twitter.com/Road_Worrier and blogs.newsobserver.com/crosstown. Please include address and daytime phone.

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