MBTA advisory: Pack light

Hoping to bolster security and still make public transit an attractive option during the Democratic National Convention, the MBTA yesterday rolled out new signs, a platoon of ambassadors to guide riders, and announced tough restrictions and inspections for all bags taken on board that week.

Riders on the Orange Line and T buses that travel on Interstate 93 and pass by the FleetCenter, for example, will be banned from carrying anything larger than a pocketbook or briefcase, and all permitted bags will be searched on those trains and buses. On all other lines, pocketbooks, briefcases, backpacks, and packages will be subject to random search. Those who refuse to be searched will not be allowed on. Large bags, suitcases, and gift totes will be inspected in every case.

Generally, the T's approximately 1 million weekday riders will be discouraged from taking bags, especially large bags, onto the system the last week of July, including those going to and from the airport with luggage, said Michael Mulhern, general manager of the Massachusetts Bay Transportation Authority.

"We're going to great lengths to make this as unobtrusive as possible," he said. "My hope is that it will be simply a quick look in a bag."

The extraordinary measures, which are in addition to the closure of North Station and the resulting cutoff of commuter lines north of the city, are designed to prevent an attack on the Boston-area transit system like the one that killed 191 people in Madrid March 11, Mulhern said. Homeland security officials have urged the T to take the precautions because both rail systems and cities hosting political conventions may be targeted this summer.

At a press conference yesterday, Mulhern said the T would distribute a new pamphlet, "Using the T During the DNC," make more system maps available, and increase information on convention week on the MBTA's website, www.mbta.com. He touted increased service, such as extra commuter trains to accommodate people who leave work early, and rush-hour level subway service all day and night. And he introduced 200 ambassadors dressed in yellow shirts and navy blue caps who will be deployed throughout the region, and new trailblazer signs guiding people around the system.

Using mass transit will be key, Mulhern said, because of planned road closures, including the shutdown of I-93 and roads that feed into it from 4 p.m. to midnight.

Mulhern acknowledged he was urging people to use mass transit during the convention while at the same time subjecting them to security-related delays and inconveniences never before seen on the system.

"It's a conflicting imperative, but we try to balance all that," he said. "One extreme would be no security; the other extreme would be so much security it impacts our ability to achieve our core mission. We're hoping people will understand and tolerate any inconvenience, especially given what happened in Madrid."

Riders will get a taste of the new security procedures beginning next week, when four teams of four officers will fan out to different subway and commuter rail stations every day and randomly stop passengers to inspect their bags, using either an explosives detection device, a bomb-sniffing dog, or by hand.

The T is the first transit system in the country to inspect bags. After the terrorist attacks of Sept. 11, 2001, airports have tightened security with thorough checkpoints. But mass transit systems have millions more people moving through them, so an airport-style system wouldn't work.

In forging the new policy for the weeks leading up to the convention and for convention week itself, T officials focused on baggage inspection, in part because the Madrid bombers left the explosives in backpacks placed on 10 commuter trains.

The Orange Line and the buses that use I-93 were singled out for the tightest measures, because those trains and buses pass close to the FleetCenter. To prevent explosives from being hidden in baggage and detonated while passing the venue, T officials decided to ban large bags outright and to inspect all smaller bags.

Orange Line cars will go by the FleetCenter underground, but will not stop during convention week, because the North Station subway station will be closed. Buses on I-93, mostly traveling to and from South Station, will pass within 40 feet of the convention venue.

The special restrictions will apply to the Orange Line between Haymarket and Community College stations, to bus routes 325, 326, 352 and 354, and to the shuttle buses taking Lowell commuter line riders from the transfer point in Woburn into Boston on I-93. The measures will affect 160,000 Orange Line riders, 1,340 riders on the four bus routes that use I-93, and 6,400 passengers on the Lowell commuter line.

All the security measures are in addition to termination of commuter lines north of the city, requiring time-consuming transfer to buses or the subway.

Anthony Flint can be reached at flint@globe.com.