An attack on the Prince Kuhio Federal Building from Honolulu's planned elevated commuter train is "most improbable," according to an ongoing threat and vulnerability assessment being conducted by the city.

Two federal officials have asked the city to shift the route of the planned $5.4 billion elevated commuter train away from the building because of security concerns. In a recent letter to City Council members, U.S. District Judge Helen Gillmor said the currently proposed route down Halekauwila Street exposes the nearby courthouse to a potential terrorist bombing or attack by an individual holding a grudge against a particular judge. U.S. District Marshal Mark Hanohano also signed the letter.

However, according to a draft threat assessment by the city, the train is not likely to serve as a platform for a terrorist attack. This assessment was started last year and is being done in conjunction with the Honolulu Police Department and city consultant Parsons Brinckerhoff.

The city said the threat assessment report may be available to the public once it's completed. However, the city did provide a summary of the report that states: "As a result of this evaluation, the possibility of an assault from the viaduct to the courthouse is deemed to be most improbable for many reasons, including: lack of access to viaduct, easy detection of trespassers, lack of sufficient time to plan an attack, lack of time to carry out an attack, lack of a plausible escape route by a perpetrator, challenge of coordination between train schedules and target availability, and alternatives for accomplishing such an assault which would have significantly less risk of failure."

A draft of the report has been provided to Gillmor and further discussions to address security concerns are planned for the future, said city spokesman Bill Brennan.

Gillmor last week reiterated her earlier concerns that the guideway structure, which will be at the same level as the windows of three judges' chambers, will increase the risk to judges and the courthouse. She pointed to the 1995 bombing of a federal building in Oklahoma City and the 2004 commuter train bombings in Madrid, Spain, as examples of the risk. And last May, the federal courthouse in San Diego was struck by a nail-filled pipe bomb.

No one was injured in the San Diego incident. However, the Madrid bombing killed nearly 200 people, and the bombing of the federal building in downtown Oklahoma City claimed 168 lives.

"We are concerned about what has happened in other federal courts," Gillmor said. "Federal judges on occasion are targets and the proximity of the rail on Halekauwila to the federal courthouse and building is of continuing concern."

Gillmor has asked the city to shift the train's route to Queen Street, King Street, Beretania Street or elsewhere.

So far, the city remains committed to the current route. However, the city said it plans to take security measures that will create significant challenges for anyone attempting an assault from the viaduct.

Security planning is ongoing and will continue to be updated and refined, the city said.

The city's threat evaluation team includes a Parsons Brinckerhoff force protection specialist with Department of Defense experience, a PB senior security specialist who was a former Transportation Security Administration executive for mass transit, and a PB senior safety and security specialist who was a former Federal Transit Administration director of safety and security. All of these specialists have conducted numerous vulnerability assessments for transit systems.

The evaluation process included examining similar systems, including the Miami Dade People Mover, Detroit People Mover and Seattle Monorail. All three travel close to buildings, in some cases within 50 feet, according to the city. The Detroit People Mover is adjacent to a federal courthouse. The systems reviewed had experienced no known threats or incidents or attempted incidents, the city said.

Under city plans, construction of the East Kapolei to Ala Moana rail will start in December. However, construction is not expected to reach the Downtown area for several years, giving officials time to resolve the courthouse security issue.

City Councilman Charles Djou has introduced a resolution recommending changing the train's route. That bill has yet to receive a hearing by the council's Transportation and Planning Committee.

"HPD's assessment (of the threat posed by the train) obviously doesn't square with the U.S. marshal's assessment," Djou said. "I think this deserves a public hearing so we can air all of these concerns and figure out which way is the best way to go."