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For more frequent trains, T needs high-tech signal system

Last month’s announcement that the Commonwealth will purchase 284 new subway cars to replace the decades-old trains on the Orange and Red lines is great news for Boston. But it’s only the first step in bringing first-rate public transportation to the Hub. What will actually determine whether the MBTA becomes world-class is capacity. Boston’s economic future is tied, in large part, to the T’s ability to decrease the time between trains, and increase the number of people each train can safely hold.

The company that won the award, CNR MA, is a subsidiary of China CNR, one of the world's largest train manufacturers. As part of the bidding process it agreed to open a plant in Springfield to assemble the trains. The fact that CNR MA significantly underbid more established competitors for the contract, such as Canada's Bombardier or South Korea's Hyundi Rotem, shouldn't be seen as a sign of inferior quality. CNR has a history of providing very well-built subway cars to major metro systems in Asia, including Beijing and Hong Kong.

The new trains, which will be delivered starting in 2018, will be a boon to the T. But the real opportunity to improve service will be in an upgrade of the T's signal system, which is planned to coincide with the delivery of the new cars. This isn't as sexy as ordering flashy new trains, but getting the planned upgrade right could revolutionize service on the Red and Orange lines.

Signal systems are the brains of any rail operation: They tell train drivers when to stop and go, and protect riders by keeping trains a safe distance from each other. The signaling technique used on the Red and Orange lines is called block signaling: Train tracks are divided into discrete areas called blocks, and the signal system makes sure that only one train will occupy a block at any given time.

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Block signaling is safe and reliable. But it limits a rail system's overall capacity by keeping trains farther apart from each other than they need to be. A system called communications-based train control solves that problem by using telecommunications technology to track where trains are relative to each other. That's the type the T should choose; implementing such a system will do much more to increase the capacity of the T than buying new rail cars.

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Currently, the Red Line only manages one train every nine minutes during rush hour. The Orange Line fares slightly better, with one train every six minutes. In addition, both lines are already over-capacity, and the problem will only increase as Greater Boston's population grows. Increasing the speed of the trains will help, and the new cars are expected to be faster than those currently in service. Still, the antiquated signal system will only allow a minimum of four and a half minutes between trains. A communications-based train control system will improve the times. The London Underground installed it recently on its Jubilee Line, and commuters can now expect a new train on the platform every two minutes during rush hour.

Boston can have similar service. The MBTA is already expecting to upgrade its system and it should make the investment in a communications-based train control system. The Red and Orange lines are vital arteries in the regional economy, connecting residential neighborhoods to Downtown Boston and Kendall Square. But unless service on these lines is improved and capacity is increased, the T will start to become a liability. Slow, unreliable trains force more people into cars and buses, further crowding already congested roads. Installing a state-of-the-art train control system will go a long way to fixing the T.