The Gateway project was unveiled early last year, about four months after Gov. Christie canceled another rail-tunnel project, the ARC (Access to the Region's Core) tunnel, citing its costs.
On Tuesday, the Government Accountability Office released a report with lower cost estimates and a smaller financial share for New Jersey than those cited by Christie when he killed the ARC tunnel.
Boardman said Wednesday that the GAO report, which said the existing 100-year-old Hudson River rail tunnels "cannot meet the access and mobility demands of the future," buttressed the case for Amtrak's Gateway project.
"If we don't get our infrastructure improved, we're going to have problems growing anything in the Northeast," Boardman said in an interview. "We're out of space - in the tunnels, on the tracks, in Penn Station."
"There has to be a change in the attitude and discussion about transportation in this country" and the role of railroads.
Funding for the Gateway project, and for Amtrak, remains uncertain, with Congress sharply divided over continuing subsidies for the national rail agency.
Boardman cited Amtrak's growing ridership - up 44 percent since 2000 - as evidence of its value.
New ridership numbers released Wednesday showed Amtrak passenger traffic was up 3.7 percent in the first six months of the fiscal year (October through March).
Amtrak has set ridership records in eight of the last nine years, including last year, when it carried 30.2 million passengers.
The most recent numbers show ridership was up 5.2 percent on the Northeast corridor, including an 8.2 increase on Northeast Regional trains and a 1.3 percent decline on Acela Express, the fastest and most expensive of Amtrak's trains.
Boardman said the decline in Acela ridership may have been caused by the mild winter in the Northeast, which allowed some weather-wary travelers to return to autos and planes. He also noted that improved Internet service on the cheaper Northeast Regional trains was now better than on Acela trains, which may have lured some riders away from Acela.
Ridership on the Philadelphia-to-Harrisburg "Keystone" route was up 4 percent for the six-month period.
Contact Paul Nussbaum at 215-854-4587 or firstname.lastname@example.org .