Gov. Andrew Cuomo has asked for a review of the East Side Access transit megaproject to learn why it costs so much. The same question could be asked of Amtrak's Gateway. In fact, the mistakes made in the design of East Side Access could be avoided in Amtrak's project if our railroads work together.

This is no small task. It would require a tunnel between Penn Station and Grand Central Terminal and an agreement for New Jersey Transit, Metro-North and Long Island Rail Road to seamlessly share it. It sounds ambitious, but it would ultimately save money while enhancing riders' access to the region.

Lack of cooperation between our various rail agencies delays projects and inflates costs. Consider East Side Access, which will connect the LIRR to Grand Central: Conceived in the 1950s, it was started and stopped in the 1970s and restarted in 2007. It has seen the opening date pushed back nearly a decade, to 2022, and costs triple, to $11 billion. One reason for this outrageous sum is that the LIRR had to build an eight-track facility 100 feet beneath Grand Central because Metro-North did not want to share the terminal—despite both railroads being divisions of the Metropolitan Transportation Authority.

The same issue is bubbling up on Gateway. When NJ Transit was working on Access to the Region's Core, a project Gov. Chris Christie canceled in 2010, it found that 35% of its riders wanted access to Grand Central. But it could not get permission to share Metro-North's Grand Central or LIRR's East Side Access. Gateway has that problem too. As a result, NJ Transit plans to build six tracks south of Penn Station, costing billions of dollars.

Connecting the operations of the railroads would simplify Penn Station's operations and eliminate the need for Penn South, where trains would merely turn around. For Cuomo and Gov. Phil Murphy, connecting these two initiatives would be an achievement on par with the merger of the subways in 1947.

Riders west of the Hudson would get one-seat access to Grand Central, Citi Field and LaGuardia and JFK airports. LIRR riders could take one train to Newark airport and Met Life Stadium. The congestion at Penn Station would be eliminated as the railroads figure out how to run trains between New Jersey and Long Island rather than terminate in Manhattan.

The MTA and NJ Transit already have a cooperation agreement for service on the Port Jervis and Pascack Valley branches of Metro-North. This can be a model. Other issues related to power, signals and the training of crews would need to be resolved, but that beats the alternative of spending billions digging out a station beneath Manhattan.

Merging transport agencies is not a new concept. The subway merger combined three distinct operators: the Interborough Rapid Transit, Brooklyn Manhattan Transit and Independent Subway lines. Paris integrated its commuter-rail systems in 1977. Philadelphia combined the Reading and Pennsylvania commuter lines in 1984, and Boston just finished a study to connect North and South stations. London has already opened Thameslink (a north–south link) and is in the final stages of building Crossrail (an east–west route). It can be done.

The costs for East Side Access got out of control because we did not think regionally and make the highest and best use of Grand Central Terminal. Cuomo could apply that lesson to Gateway and avoid the boondoggle that would be Penn South by finally linking Penn Station to Grand Central.

Joining the goals of East Side Access and Gateway will force greater cooperation between the railroads and make commuter rail in New York more customer-friendly and regional, as it is in Paris, London and Philadelphia.

The governor is right to review East Side Access. But he must add Gateway to his inquiry and chart a future that puts customers and taxpayers first.

Bob Previdi is a transportation lobbyist and a former planner and spokesman at NYC Transit.