The Regional Plan Association produced a nice explainer video on why the region needs to build more rail capacity under the Hudson River, the risks facing the existing train tubes, and what will happen if one of them has to be taken offline for repairs before another tunnel gets built.

The situation with the tunnels has heightened urgency because New Jersey Governor Chris Christie killed the ARC rail tunnel project so he could pay for roads. Not that New York’s Andrew Cuomo has been much help either: When pressed by reporters last summer, Cuomo abdicated responsibility for the century-old rail tubes.

Eventually, Christie and Cuomo said their states would foot half the bill if the feds picked up the rest, but no one really knows how much the project will cost.

The video is part of RPA’s campaign to prod state and federal leaders to action on expanding Hudson River rail capacity. Senator Cory Booker will participate in a related roundtable tomorrow.