WASHINGTON — In the nearly four years since the Sept. 11 attacks, security experts scouring American cities have found -- as London learned Thursday -- that public transit systems are among the most vulnerable and most difficult targets to defend from terrorists.
Yet such systems have received just $250 million in federal funding to beef up security since 2001, compared with $18 billion for the nation's airports. Regional transit systems have spent $2 billion of their own on security enhancement, industry officials say, but have identified $6 billion more in needed improvements.
Local officials have taken steps. In Southern California, for instance, transit operators have built security fences along some stretches of rail, installed sensors and cameras at stations and stepped up patrols.
New York City officers are sometimes assigned to every train at rush hour. The nation's capital has sensors to detect chemical attacks. In San Francisco's Bay Area Rapid Transit system, SWAT teams conduct random patrols.
But officials nationwide acknowledge that because buses and trains must be easily accessible to riders, it is nearly impossible to completely secure them.
"You do everything humanly possible to ensure people's safety. But it's an open society," said New York transit spokesman Tom Kelly. "You could do it like the airport, but nobody'd get there."
Thursday's attacks reignited debate over whether considerably more money should be spent on measures that officials argue could increase safety -- and, if so, where the money would come from.
Transit has proved to be one of the toughest cost-benefit analyses in all of homeland security: Could massive capital expenditures really bring large improvements in security?
Many measures taken so far support general crime prevention as well as accident and disaster responses. But some expensive new systems sought by transit officials would be helpful only against terrorism.
"We're all kind of concerned that we may not be as equipped as we need to be," said Richard A. White, general manager of the Washington Metropolitan Area Transit Authority, the nation's second-largest subway system. "We really feel like there hasn't been enough attention at the federal level."
Some terrorism experts say the federal funding disparity between mass-transit and air-travel security makes sense because the Sept. 11 attacks targeted airlines and because airports are far easier to secure than subways, trains, buses and ferries.
"We cannot realistically apply an aviation security model to surface transportation," said Brian Michael Jenkins, director of the Mineta Transportation Institute's National Transportation Security Center in San Jose and a terrorism expert at the Santa Monica-based Rand Corp. think tank.
"We have about 800 million passenger boardings a year on airplanes. We have 430 commercial airports," Jenkins said, compared with about 25 billion boardings on buses, trains and subways each year. "It would take an army" of screeners to check public transit passengers.
But public transit advocates said there were steps that would make the system significantly safer -- and would not bankrupt the federal government.
"We think public transit riders are being treated as second-class citizens," said Rose Sheridan, a vice president of the American Public Transit Assn., which represents regional transit systems.
Local transit officials have wish lists of projects they say would enhance their ability to thwart a terrorist attack, as well as other dangers.
They would like to purchase new communications systems and to install more closed-circuit cameras on trains and city buses. They would like intruder detection systems at tunnel openings and other entrances. And larger cities want to install automatic chemical and radiological detectors like equipment used in Washington.
But few agencies have the resources to buy that kind of equipment.
Public transit agencies are funded by a combination of local, state and federal money. Fares provide about 36% of operating funds -- which pay for personnel and the like -- with state and local governments making up nearly all the rest. But when it comes to capital funding -- which covers buildings, vehicles and so forth -- the largest single source is the federal government, which provides 47%.
"The greatest challenge funding-wise is for capital measures," said Greg Hull, the American Public Transit Assn.'s director of operations, safety and security. "Our systems are limited in their ability to force such funding."
Because public transit systems are designed and operated regionally, there have been few national efforts to assess their vulnerability to a terrorist attack or to assess how much it would cost to make them safer.