New York’s L Train subway line carries more than 225,000 riders daily between Brooklyn and Manhattan, but that comes to a 15-month halt in April 2019 when the subway line shuts down to repair storm damage to the tunnel below the East River.

That’s a ton of riders who will have to find an alternative commute, stressing an already overworked system. While the city’s transit authority has proposed increasing service for other subway and bus lines and adding ferries to ease the pain, one outside team has come up with a more radical — and, in this case, ancient — solution.

The cutely named L-Ternative bridge, which launched a Kickstarter campaign this week, proposes building what’s known as a pontoon bridge across the East River. Instead of a permanent structure, this bridge would be temporary, with about three dozen barges anchored in place to support it.

roman pontoon bridge
A Roman pontoon bridge.

Pontoon bridges have been a vital part of military strategy for millennia, with their earliest documented use dating back to ancient China some 3,000 years ago. The Greeks, Romans, and Persians used the technology to build temporary bridges across water from the Bosphorus in modern-day Turkey to the Danube in Central Europe. The Mughal emperor Akbar the Great rode his war elephant across a pontoon bridge in the 16th century, as depicted in the painting up top — though that bridge collapsed as he crossed it. The L-Ternative would be made of stronger stuff, but probably best to keep elephant traffic to a minimum, just in case.

The planned bridge would feature pedestrian walkways and a pair of bus-only traffic lanes to replace the suspended L train service during the repairs, which are set to run until at least July 2020. The buses would potentially run from underground stations built to connect with the current Brooklyn and Manhattan terminuses for the L train, allowing for relatively seamless commuting.

The proposal estimates it would take six to eight months to build — which means there would be time to pull this off before the planned shutdown 14 months from now — and could be paid off with a $1 toll.

pontoon bridge akbar
Mughal emperor Akbar the Great riding the ferocious elephant Hawa'i, pursuing another elephant across a collapsing bridge of boats (left), in Basawan and Chetar Munti's "Akbar's Adventure with the Elephant Hawa’i", from 1561

The plan is the brainchild of real estate investor Parker Shinn, who hopes to raise $50,000 on the month-long Kickstarter. The goal isn’t to crowd-fund the construction of the bridge, the cost of which would likely be in the tens of millions, but rather to demonstrate serious community support for such a project and to pay for putting together a concrete plan the city can review. As of Wednesday, the Kickstarter has 33 backers and has raised $3,223, with a little more than three weeks to go.

The L-Ternative bridge is one of several proposals for what to do while the tunnel is closed. These include adding more bus lanes to existing bridges, expanding ferry services, and even building a gondola to link Brooklyn and Manhattan.