What Traffic Jam?

Boston, MA-People in Boston either talk about how the Red Sox are doing or the traffic. But since the I-90 tunnel extension to South Boston opened in January and the I-93 northbound tunnel beneath downtown opened in March-two major elements of the now infamous "Big Dig" project-they only have one of the two to complain about. Rush hour, which used to span 10 to 12 hours, has been cut in half.

Massachusetts Turnpike Authority (MTA) officials say large parts of the Big Dig's (www.bigdig.com) $200 million integrated project control system (IPCS)-the brains that keep traffic moving-are plugged in, turned on, and performing flawlessly. As you cruise the new tunnels-some of which dive 120 ft below street level-you're watched by scores of cameras. Your speed is tracked.

Your vehicle height is checked. And the quality of the air you breathe is sniffed. If there's trouble ahead, electronic signs will tell you how to avoid it. Even the broadcast on your car radio can deliver safety messages.

To prove out the system, State Police recently put the IPCS through its paces during late night tests by deliberately halting traffic to fill the tunnels with idling cars. All systems checked out okay.

Tunnel vision

The $15 billion Big Dig is the largest public transportation project in the United States, constructing and rebuilding 161 lane miles of interstate highways, half of which are in tunnels.

Honeywell Technology Solutions Inc. (www.honeywell-tsi.com) developed and installed the Big Dig's nervous system. "They call us the rocket scientists," says George Gram, HTSI's Director of Intelligent Transportation Systems. In addition to highway systems, HTSI manages satellite operations and related ground facilities for the U.S. Air Force and NASA, including the Hubble Telescope.

Given Honeywell's resume, it's no coincidence that the Big Dig operations control center (OCC) resembles NASA Mission Control. One wall is taken up with 19 large rear projection television screens. Fifty-four 21-inch monitors glow with video feeds, maps, building schematics, utility configurations, and other data. There are eight workstations from which operators can call up any camera or device they choose.

The OCC is the nexus for the detection, collection, and interpretation of huge amounts of data, all in real time. By the time the Big Dig is completed in 2004, there will be 413 digital color cameras, 35,000 loop detectors, air quality detectors in 35 zones, and 45 laser height detectors tied in. All told, the 'smart' highway system will have more than 40,000 SCADA (supervisory control and data acquisition) devices feeding telemetry to computers every three seconds.

The system is fully redundant, with a mirror back-up computer running at all times. In a nearby building there is even a second OCC akin to the starship Enterprise's "emergency bridge."

"You'll find some highway control centers with some of the systems we have, but there's not a more comprehensive system in operation today," says Michael Swanson, Chief Engineer and Chief of Operations for MTA. "We can control every single system on the project from the OCC."

Keeping things moving

While all the bells and whistles may seem like overkill, officials says they're essential for moving the 245,000 cars a day that will use the tunnels.

"In a closed environment, the consequences of any problem are multiplied," says James Murphy, MTA's Operations Manager. "We're able to spot incidents within 2 minutes, dispatch a tow truck within 8 minutes, and have the disabled vehicle out within 15 minutes."

The loop detectors are the front line of the IPCS. The technology is deceptively simple: the metal frames of passing vehicles modulate the current in 120V energized hexagonal wire loops embedded every 16 ft in each lane. These signal modulations are picked up by local field controllers and relayed to the OCC computer. Things get more sophisticated as the computer runs the signal patterns through algorithms to calculate speeds for each lane.

When the computer spots a slowdown (usually 20% or more below posted speeds), it sends an alarm to the operator and automatically pans and zooms cameras in the vicinity toward the suspected problem. Almost instantly, video feeds of the area are routed to the operator's console, and a menu of options for handling the situation appears. Gram says operators can usually handle typical incidents with a few clicks of a mouse.

"Software automation really speeds up response time," say Murphy. "Within seconds the operator can have a map or schematic diagram of the affected area or building up so they can respond. That's the heart of the human operator's job-verifying and responding to problems." Operators can also call up any of the 130 electronic message signs to reprogram text messages and close lanes by switching the green arrows on overhead lane usage signs to red Xs.

Video data travels over a 492-mile optical fiber network that has a data handling capacity exceeding 50 Mbyte per second. Voice and data signals are also multiplexed over the network, which operates on fiber-optic digital interface (FDDI) and standard Ethernet protocols.

Tow trucks and police cruisers are poised in discrete "perches" throughout the tunnels, and OCC operators have direct radio contact with them. Two-way radio intermodulation problems (tunnels act as waveguides, disrupting normal communication) have been resolved by using two parallel antennas in the tunnels.

The IPCS also provides full rebroadcast of the AM and FM radio spectrums inside the tunnels. AM signals are redistributed via wires running the length of the tunnels; FM signals are rebroadcast from ominous black paddles affixed to the walls. Operators can interrupt the signals and broadcast messages on all frequencies. Continuous highway advisory radio broadcasts can be heard at 530 AM.

Cellular phone service is still limited, but MTA will issue a request for tunnel cell telephone contractors next year. There's also a $6 million security add-on planned for motion detectors and low-light cameras at key project facilities to help guard against terrorism. Within 10 years, MTA hopes the loop detectors will be replaced by video recognition technology that will allow the OCC computer to gauge traffic speed and volume by watching the video feeds.