The Ada Resource Association
New York City Builds New Subway Line with Ada

When the Metropolitan Transportation Authority of New York City (NYCT) chose MATRA Transport International to modernize the Carnarsie Line of the New York City subway, one of the French company's winning points was its use of Ada.

Six companies responded to NYCT's request for proposals. According to Dr. Nagil Ghaly, Program Manager and Chief Signal Engineer, he and his staff winnowed out three of the contenders in part through the SEI's Software Capability Evaluation.

"Three companies had existing systems or were in process of developing what we were looking for," Ghaly said. "We also had a working subway line for them on which to build and demonstrate a prototype system."

After a two-year selection process, Matra was chosen from the three finalists on the basis of technical sophistication and experience, price, prototype testing, and the maturity of their successful system.

An Ada Success

As with the Paris Meteor, Matra will design and build most of the Carnarsie Line's new software in Ada, and all of its critical components. Much of the software will be reused. "They're selling us a turnkey system," Dr. Ghaly explained. "They're writing the software, integrating it, installing it in equipment rooms and trains. It will be done by them under our supervision."

As of May 1999, 1430 trains were running world-wide with Matra Transport international automatic control systems. Over 900 million people had been transported without a single accident on Matra Transport International's automatic control systems, which are written mostly in Ada.

Due in 2004, the three Ada systems for New York City's oldest subway line include the Carborne Equipment Subsystem, the Digital Communications System, and the Zone Controller Subsystem. All the systems include touch screen LCD color consoles, which conventional push buttons and switches complement as a backup.

The Carborne Equipment Subsystem, or "onboard" system, will be installed in each car. The Zone Controller system sends the Carborne Subsystem data on the train's location, on what track it is riding on, the typography (curves and grades) of its route, the speed limits, and also the "limit of authority," which is how far the train is authorized to go. The onboard system then is tasked to determine the speed profile of the train. If the train is on manual mode and the driver goes above the speed limit, then it provides "overspeed protection."

Data Communication

Dr. Alan Rumsey, IEEE working group leader of the Rail Transit Vehicle Interface Standards Committee (RTVISC), explained the Communications system as follows: "Matra's DCS (Digital Communications System) consists of three sub-networks--the Wayside Sub-Network, the RF Distribution Sub-Network, and the Carborne Sub-Network. The common protocol and interfaces on the wayside are based on an IP set of standards and the Carborne network uses LonWorks technology."

The "Wayside" is the same thing as the train's own controller. The communication subsystem allows the various trains in the area to communicate with Zone Controller, which is a third subsystem. It is a spread spectrum system, at a frequency of 2.4 gHz. The information transmitted and received is what was listed for the Carborne Subsystem: train location, speed limits, etc..

Zone Controller Subsystem

The Zone Controller consists of a database for the entire region, which will include the track profile, grades, curves, train speed, and wayside equipment; i.e., switches and signals. The Zone Controller receives information on train locations; will provide movement authorities based on the status of the switches and signals and location of other trains; and receives and relays information with the trains.

An auxiliary wayside system provides for the movement of trains from one track to another, for which someone must operate a switch. However, the Zone Controller indirectly transmits data, or "talks" to the switch, by talking to the relay system that talks to the switch. The relay system determines if a switch can safely be thrown based on the location and speed of the other trains, which is based on the Zone Controllers' data. Because the Zone Controller makes these determinations, it needs to receive constant data from the trains to keep them and their passengers safe.

While Matra's experience in modernizing existing subways in Paris was crucial to New York's needs, the language also played a part. Software Lead for the project and an experienced Ada programmer herself, Sofia Georgiadis said, "There are very basic reasons for using Ada for safety critical applications, and for those reasons the language and the company were both good choices."

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