It's a bit dark but the ghosts of Bergen St are visible this weekend as Manhattan-bound F trains run express. A video posted by Second Ave. Sagas (@secondavesagas) on May 14, 2016 at 4:41pm PDT

Every now and then, due, at times, to the never-ending rehabilitation of the Culver Viaduct or other track work in the vicinity, the F train in Brooklyn runs express between Jay St.-MetroTech and some station farther south. The transit cognoscenti know to look out for glimpses of a ghost station once that F train nears or leaves Jay St., and over the weekend, as the F went express, an eagle-eyed observer could catch the the abandoned lower level at Bergen St.

As ghost stations go, the Bergen St. lower level is hardly a secret. Multiple doors that are often kept unlocked dot the upper level at Bergen St., and the 1999 fire at that station earned headlines. For those in Brooklyn fighting for the restoration of the F express service, the Bergen St. station may or may not be the lynchpin. Trains can bypass the Bergen St. station, but as you can barely see from the video I shot over the weekend, there’s not much there. The station is an abandoned mess of darkness, and the MTA has used parts of it for storage. Yet, it’s future is as intriguing as its mere existence, a shadow of subway past.

The idea behind the F express service is one I have explored at length in the past, and it’s one that has garnered recent attention. The MTA apparently has a report on the idea sitting in a proverbial drawer, and this report has possibly been sitting in this drawer for three years. Yet, no one has seen the report, and politicians have again been agitating for F express service. The idea is an obvious one: The MTA could use dormant and pre-existing infrastructure — in this case, express tracks along the Culver Line to improve service to those more remote areas of Brooklyn. For some commuters, rides could be shortened by 5-10 minutes.

But there is a rub; there is always a rub. As currently configured, F express service would lead to reduced service for some of the F’s busiest Brooklyn stations. Carroll St., Smith-9th Sts., 4th-9th Sts., and 15th St.-Prospect Park, to name a few, would see less frequent F train service, and the ridership from those stations far outpaces the number of riders who would gain a few minutes from the express service. If the MTA can’t rehabilitate the lower level at Bergen St. to permit passenger service — an undertaking that would be quite expensive, according to 2012 comments from one Transit official, another 11,000 riders would see F service slashed. Simply put, based on current load guidelines, the MTA cannot add F express service while maintaining local service frequencies that handle customer demand.

So why not, you may ask, just run more F local trains? It seems like a simple solution, but it’s not quite that easy. Most importantly, the MTA would need additional Manhattan and East River capacity to run more F trains, and based on various F service patterns — interlining with the G in Brooklyn, the M in Manhattan and the E in Queens — the route cannot support additional trains. Second, the MTA doesn’t have the rolling stock to add F express trains. That’s a more solvable, albeit an expensive one, for a solution that seems to create more problems than it solves. Of course, with an additional East River crossing — perhaps a Phase 5 of the Second Ave. Subway were we all to live that long — the problem would be resolved, but now we’re talking in decades rather than years.

Word is that the MTA’s own studies on the F express plan show little to no net travel gains from the F express plan, but the idea is a political hot potato that the agency isn’t comfortable quashing quite yet. So the idea percolates every few months or years as that idea that will save Midwood from its schleppy F train service. I can’t blame anyone from hoping, but that lower level at Bergen St. seems more like a taunt that a promise of future service. Every now and then, we get a glimpse of a different plan, but it remains out of reach, perhaps for good reason.