Between 2001 and 2010, more than 2,500 New York subway cars were sunk into the Atlantic — decades later, they have become a thriving underwater reef

Between 2001 and 2010, more than 2,500 retired New York City subway cars were deliberately sunk into the Atlantic Ocean, transforming obsolete trains into artificial reefs along the U.S. East Coast.

Instead of being scrapped after decades of carrying passengers through New York, the subway cars were cleaned, prepared and transported offshore, where they were lowered onto designated reef sites. Over time, their steel frames became covered with marine organisms and attracted fish, creating underwater habitat on stretches of seabed that were otherwise largely made up of sand and sediment.

The unusual recycling project stretched from New Jersey to Georgia, with several coastal states using the retired subway cars as part of their artificial reef programs.


One of the largest concentrations was created off Delaware, where 997 retired New York subway cars were sunk between 2001 and 2010. The site became known as Redbird Reef, named after the red-painted subway cars that once operated across New York City.

Today, the submerged trains serve a very different purpose from the one for which they were built.

From subway cars to underwater reefs

The idea behind the project was straightforward. Large portions of the Mid-Atlantic seafloor are relatively flat and consist largely of sand or mud, providing limited hard surfaces for marine organisms to attach to.

A subway car changes that.

Its steel exterior, doors, windows and interior spaces create surfaces and cavities where organisms can settle and fish can find shelter. Algae, mussels, barnacles, sponges and other organisms gradually colonize the structures, creating a food source for larger marine animals.

The process can begin surprisingly quickly.

According to the U.S. Fish and Wildlife Service, algae can appear within weeks, followed by invertebrates and fish over subsequent months. Within roughly one or two years, an artificial structure can develop into a functioning reef community.

The subway cars also provide physical refuge. Fish can swim through the open doors and windows and use the interior of the cars as shelter from predators and rough water.

In one New Jersey study, researchers found an average of 323 fish using each subway car after two years.

Why were New York subway cars used?

New York City Transit had thousands of aging subway cars that were being retired as newer trains entered service.

Rather than sending all of them to scrap yards, the cars offered coastal states a large supply of substantial steel structures that could be repurposed for artificial reef programs.

But the trains could not simply be dropped into the ocean.

Before deployment, the subway cars underwent extensive environmental preparation. Hazardous materials and potentially polluting components had to be removed. Windows and wiring were taken out, while oils, fuels, hydraulic fluids, grease and other contaminants were cleaned from the cars.

The cleaned trains were then transported offshore and placed at approved reef locations.

The process turned an enormous disposal challenge into an unusual form of marine habitat creation.

Delaware received 997 subway cars

Delaware became one of the biggest beneficiaries of the program.

Between 2001 and 2010, 997 retired New York subway cars were sunk off the Delaware coast, forming the core of what became known as Redbird Reef.

The reef covers approximately 1.3 square miles of seafloor and became an important destination for recreational anglers and divers.

The name came from the subway cars themselves. Many of the retired trains were Redbirds, the distinctive red New York subway cars that had once been a familiar sight across the city.

Underwater, however, the trains gradually lost their original appearance.

Their metal surfaces became coated with marine growth, while fish began gathering around the structures. Open sections of the cars provided additional shelter, turning the abandoned trains into a network of underwater habitats.

Delaware subsequently expanded its wider artificial reef system using other materials, including retired military vehicles and barges.

More than 2,500 cars were deployed along the East Coast

Redbird Reef was only one part of the much larger experiment.

New York City Transit deployed more than 2,500 retired subway cars at permitted artificial reef sites between August 2001 and April 2010.

The cars were distributed among reef programs rather than being placed at one enormous underwater site. States along the East Coast used the trains to create additional structure on offshore seabeds and attract marine life.

Delaware received a particularly large share, but subway cars also became part of artificial reef projects farther south.

The scale of the project meant that thousands of objects originally designed to move people through an urban transportation network were suddenly serving as stationary structures in the marine environment.

The ocean quickly began taking over

Once the subway cars reached the seafloor, natural processes took over.

Marine organisms began attaching themselves to the exposed steel. Algae and other organisms formed the early layers of the developing ecosystem, followed by invertebrates and fish.

The structures effectively became foundations for a food web.

Small organisms attracted fish, while larger fish were drawn to the shelter and feeding opportunities created by the reef.

Artificial reefs can therefore provide substantially more biological structure than an otherwise featureless sandy seabed.

Delaware has reported that invertebrate communities on its artificial reefs can provide up to 400 times more food for fish per square foot than bare ocean floor.

The subway cars also created new locations for recreational fishing and diving, concentrating human activity around designated artificial reef sites.

Scientists watched the trains change the seafloor

The project was not simply about creating places for fish.

The submerged subway cars also gave researchers an opportunity to study how large structures interact with the ocean floor over long periods.

Waves, tides and currents continually move sand and sediment across the continental shelf. As a result, some subway cars gradually became partially buried.

Researchers monitored how sediment accumulated around the structures and how the surrounding seabed responded to their presence.

A peer-reviewed study published in Continental Shelf Research examined these changes and found that the structures eventually reached a relatively stable condition, with the surrounding seabed adjusting through patterns of erosion and sediment deposition.

Such research is useful because artificial reefs must remain stable enough to continue functioning as habitat.

Not every subway car survived equally well

The experiment also revealed an important problem: not all subway cars were equally suited to life underwater.

The older Redbird cars generally performed well in deep water. Robert Martore, artificial reef coordinator with the South Carolina Department of Natural Resources, said that about 90% of the Redbirds remained intact and upright after 15 years in one assessment.

Newer stainless-steel Brightliner cars, however, proved more problematic.

Many deteriorated or collapsed in less than a year in some locations. New Jersey officials had estimated in 2007 that newer stainless-steel subway cars could remain underwater for 25 to 35 years, but inspections two years later found significant structural damage in several cars.

The state subsequently postponed additional stainless-steel deployments while the cause of the deterioration was investigated.

Previously deployed Redbird cars did not show the same pattern of damage.

The contrast demonstrated that an artificial reef cannot simply be created by placing any large discarded object underwater. Material durability, environmental safety, design, location and long-term monitoring all matter.

The trains became more than discarded infrastructure

More than two decades after the first subway cars were lowered into the Atlantic, many of the trains have become difficult to recognize.

Marine organisms cover their surfaces. Fish move through their interiors. Sediment accumulates around their wheels and frames.

The subway cars that once carried commuters through New York are now stationary structures on the ocean floor.

Their transformation illustrates the basic principle behind artificial reefs: adding hard structure to an otherwise open seabed can create surfaces for marine organisms to colonize and spaces where fish can feed and shelter.

But the experiment also demonstrates the limitations of large-scale reuse.