bur-mh/ns

PARIS , July 4, 2006 (AFP) - Nearly five years after Al-Qaeda forever changed the way nations seek to protect their citizens, the world's transport networks still remain highly vulnerable to terrorist attack, experts and analysts say.

Many of the deadliest terrorist strikes this century involved public conveyance systems used by much of humanity to get from one place to another -- commercial planes in the United States on September 11, 2001, trains in Madrid and a ferry in Manila in 2004, buses and the underground in London one year ago on July 7.

But post-9/11 national and international efforts to secure transport by land, air and sea have fallen short, making vehicles of mass transit easy targets for would-be terrorists with a serious grudge and a few thousand dollars (euros) to spend.

-AIR TRANSPORT

Nowhere, perhaps, are the weaknesses in the defenses against such attacks more evident than in commercial air traffic, despite enhanced security in airports around the world.

While it may be more difficult for a terrorist to board a plane with explosives or the intention to commit a suicide hijacking, commercial aircraft remain vulnerable -- especially as they take off and land -- to external attack by cheap and easily-acquired shoulder-held rockets, notes Frenchman Eric Denece, author of "Tourism and Terrorism" and an expert on the mechanics of terrorism.

Just last month Swiss police arrested seven people linked to what federal prosecutors said was a plot to down an Israeli El Al flight in Switzerland. Unconfirmed Swiss media reports said the group planned to use a rocket launcher near the Geneva airport.

Some security experts advocate equipping all commercial aircraft with electronic decoy systems to deflect surface-to-air missiles of the kind fired in 2002 at an Israeli plane near Mombassa airport in Kenya. Such a refit would cost 11 billion dollars (8.5 billion euros) for the nearly 7,000 commercial planes in the US alone, according to the RAND corporation, a global policy think tank involved in research on armed forces, in California.

But such anti-missile systems are useless against the most primitive of rockets. "There is not interference possible against a RPG-7," said Denece, referring to the Soviet-made rocket launcher, a common item on the arms black market.

-SEA TRANSPORT

Ocean-going vessels, especially ships carrying thousands of standardized 20- and 40-foot (six to 12-meter) containers, are also easy prey, experts say.

There is little to prevent a terrorist seeking to slip, for example, a weapon of mass destruction -- such as a dirty bomb composed of conventional explosives and commercially-available radioactive material -- into a shipment of tennis sneakers or steel pipes.

"If a terrorist wants to do it, he can do it," says American Michael Wall, a former instructor at the anti-terrorism center of the US Navy and currently a maritime security consultant. "Bringing a weapon of mass destruction into a port via a merchant vessel is a very realistic scenario."

And the stakes, he said, are very high. "Any major breakdown in the maritime transport system could cost dearly in terms of lives and would fundamentally cripple global trade," he added.

-RAIL TRANSPORT

When it comes to rail traffic -- targeted in London one year ago this week and in Madrid the year before -- transport authorities can only focus on measures that will limit the number of deaths and damage from such attacks rather than trying to prevent them, experts say.

"Surface transport systems ... are difficult to protect because they are so accessible and spread out," concluded the commission on the September 11 attacks in their final reports, published two years ago.

Some measures can be taken: eliminating or hardening trash cans in stations, adding security personnel, enhancing video surveillance, using dogs to sniff out explosives.

In London, where 56 people, including the four Islamic extremist suicide bombers, died and nearly 700 were injured a year ago in multiple attacks, experimental X-ray monitors and body scanners have been installed as well.

But the sheer scale of passenger traffic precludes any kind of comprehensive solution, said Michael Brown, head of London's underground, in announcing these new measures last November.

"There are 67 million passengers each year at Heathrow airport, there are a billion that use public transport," he said.

Some critics contend that terrorist prevention dollars (euros) are not distributed equitably across different transport sectors.

In June, for example, the internal security commission of the US House of Representatives complained in a report that the nation's transport security administration spent nine dollars per airplane passenger and only one cent -- nine hundred times less -- for rail passengers.

bur-mh/ns