Humming along with technology, until it's not
Computer meltdown creates traffic-light chaos in Montgomery

By Ashley Halsey III
Washington Post Staff Writer
Thursday, November 5, 2009

In the backdrop of so much of 21st-century life, computers are an unseen hand that guides the day in ways we rarely know about. Until they crash.

Wednesday provided one such rude awakening for commuters in Montgomery County.

A computer meltdown disrupted the choreography of 750 traffic lights, turning the morning and evening commutes into endless seas of red brake lights, causing thousands of drivers to arrive at work grumpy and late, and getting them home more frustrated and even later.

Montgomery County officials said they will offer free bus rides all day Thursday, a decision made Wednesday night, even as county technicians worked feverishly to resurrect the faulty machine in time for the morning rush.

"In case these efforts are not successful, we want to help provide commuters another option" by providing free access to Ride On buses, County Executive Isiah Leggett said in a statement.

On Wednesday, commuters who thought they would slip around the chaos by detouring from their usual routes only found more problems. The tangles of traffic rippled from Veirs Mill Road to Rockville Pike to Old Georgetown Road to Interstate 270 and the spur.


"At this time, the problem has not been fixed," Tim Firestine, a county administrator, said Wednesday as the last, late commuters inched toward home.

Some of the worst of it radiated from an epicenter at Four Corners, as the heavily trafficked intersection of University Boulevard and Colesville Road in Silver Spring is known.

And at dawn and dusk, cars backed up like a row of toppled dominoes once they reached the balky traffic signals on Connecticut Avenue.

That a single computer failure can plunge an entire sector of the region into near gridlock underscored how fragile and overloaded the second-most congested urban area in the country has become.

Before Wednesday, few Montgomery commuters knew, and even fewer probably cared, that a big computer in Rockville and a team of engineers working with it regulate the flow of traffic throughout the county.

"Traffic normally is so congested, and I don't think people realize how much the signals control the flow until something like this happens," said county spokeswoman Esther Bowring.

The system, which she described as "unique" in the Washington region, is based on a Jimmy Carter-era computer that sends signals to traffic lights all over the county. On weekday mornings, it tells them to stay green longer for people headed to work. And in the evenings, it tells them to stay green longer for people headed home.

It also makes them all work together -- green-green-green -- to promote the flow of traffic. That happens automatically, and then the engineers use data from hundreds of traffic cameras and a county airplane to tweak the system. When there is an accident, breakdown or water main break, they use the computer to adjust signal times further and ease the congestion around the problem.

It's great when it works, a disaster when it fails.

The first inkling that something was wrong came shortly after midnight, and as computer technicians were rushing to handle it, the computer crashed completely about 3 a.m. Wednesday.

All of the traffic lights kept working, but they no longer knew what time it was. When they were supposed to switch to morning rush mode, from 7 to 7:30, they kept rocking along at a rhythm better suited to Sunday morning.

By then, county workers had been racing from one major intersection to the next, adjusting each light by hand. But it was too late. Although a flick of a switch could fix one light's timing, only the computer had the power to synchronize a series of traffic lights.

Drivers' frustration was shared by the computer technicians in Rockville, who had isolated the problem by lunchtime but couldn't figure out how to fix it, Bowring said.

"They know where the problem is, but they just don't know what it is," she said. "The server seems to be sending the signal, but the conduit is not transferring the information to the signal lights."

The afternoon commute began badly when an unrelated fatal crash on the inner loop of the Capital Beltway ended with a vehicle in flames on the side of the road.

Bowring said the computer that went belly up Wednesday was being phased out. The county is in the second year of a six-year program that will bring in more modern and reliable equipment.

The malfunction of the Montgomery computers in Rockville happened about the same time as, and a couple dozen miles away from, a power failure at Metro's headquarters that muddled the morning commute for bus and rail riders.

"I called them first thing when I heard about it," Bowring said, "and asked if there could be any possible connection. They said: 'No. There's no conspiracy out there.' "

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