A few readers have written in asking about the disappearing pedestrian islands on Ninth Avenue in Hell’s Kitchen. The concrete islands next to the bike lane shorten crossing distances and slow drivers turning onto Ninth Avenue. A few weeks ago, the city started tearing them out.

What’s the deal? We checked in with the Department of Design and Construction to find out.

The good news is that the pedestrian islands are not gone forever. The bad news is that they might not be back for at least four years:

Traffic islands on Ninth Avenue from West 51st Street to West 59th Street are being temporarily removed so that new water mains can be installed. Currently, islands have been removed from West 51st Street to West 55th Street. The remaining will be removed within the next month. Construction will be completed in 2021.

DDC says the bike lane will be maintained in some form during construction.

As complex as NYC’s subsurface infrastructure may be, four years seems like an awfully long time to replace water mains on ten city blocks — and that’s if DDC stays on schedule, which is rare.