Lockheed Martin Corp. was awarded a $212 million contract to build a counter-terrorist surveillance and security system for New York's subways and commuter railroads as well as bridges and tunnels.

The Bethesda defense contractor's system is expected to include more than 1,000 cameras and 3,000 electronic sensors, according to the Metropolitan Transportation Authority.

The MTA carries an average of 7.7 million weekday riders, the most in the United States. The Lockheed contract is the largest spending commitment so far by the agency to strengthen its defenses against terrorism.

"We will be on the cutting edge of this technology in order to protect our system against terrorist attack," said Katherine N. Lapp, the authority's executive director. Lockheed's proposed system "doesn't exist anywhere else in the world, in any other transit agency," she said.

Lockheed officials said the system will provide monitoring, surveillance, access control, intrusion detection and response capabilities. The system will feature motion sensors, perimeter sensors, "intelligent video" software and conventional closed-circuit television cameras. The system will use "pixel recognition" technology, which can detect unattended packages by comparing objects in view with reference images.

Judy Marks, executive vice president of Lockheed's Transportation and Security Solutions unit, said part of the system will be operational before the end of the year, and the complete phase-one installation will take 36 months.

Marks declined to say how many cameras would be necessary to completely cover the sprawling MTA system, which includes almost 500 subway stations and more than 2,000 miles of tunnels and track.

The MTA will seek proposals for biological, chemical and explosive weapons detection in the second phase of the project, which should be designed by the end of the year, agency officials said.

The kind of integrated modular system Lockheed will be installing has never been attempted in a mass-transit network, though the various components have been used independently, and therefore have been field-tested, Marks said.

Lockheed's Transportation and Security Solutions unit is part of the Electronic Systems group, Lockheed's second-largest business last year with sales of $9.7 billion, or 27 percent of the company's total sales of $35.5 billion.

The unit has won contracts to modernize equipment at 20 U.S. air traffic control centers for the Federal Aviation Administration, and it reconfigured security checkpoints at U.S. airports after the terrorist attacks of Sept. 11, 2001.

Lockheed shares closed unchanged yesterday at $63.05 in New York Stock Exchange trading.

Police officer Russell King, left, inspects bags as people enter a New York subway station in July. The Metropolitan Transportation Authority awarded Lockheed Martin Corp. a $212 million security contract.

Lockheed's Judy Marks at contract announcement yesterday.