When leaves fall on train tracks and get crushed by trains, they leave behind a slippery, slimy substance called pectin. Like ice on the road, pectin reduces the traction between our trains' wheels and the rail. The reduced traction results in wheels slipping when accelerating, or sliding when braking. This sliding can cause flat spots on the wheels. If flat spots get too big, we need to take train cars out of service for repairs.
Pectin gets even more slippery when it's damp, such as after a light rain or in the morning dew. Wind storms that blow lots of leaves onto the tracks at once can also make the problem much worse.
This problem affects every railroad that runs where leaves fall, including both the LIRR and Metro-North. It also affects the Staten Island Railway, the lines in Brooklyn, the in the Bronx, and the in Queens.
Across the MTA, we take a three-pronged approach to mitigating this problem. However, while can reduce how often and how severely slip-slide affects our trains, we cannot completely eliminate it. We appreciate your patience.
Keeping rails clean
Each night in the fall, specialized cleaning trains run throughout the system, focusing on known problem areas. These trains use high-powered lasers or high-pressure water jets to clean the leaf residue off the rails.
At the height of the season, we will also run these cleaning trains during midday hours.
We also manage vegetation along our tracks to reduce the number of leaves that fall on them in the first place.
Minimizing flat spots
We instruct our train crews on how best to operate through slippery areas, and where problem spots tend to be. We tell them to immediately report slippery issues to the control center so trains behind them know what to expect.
On diesel trains, locomotives automatically drop sand on the tracks to help improve traction and reduce wheel slippage when it begins to occur. On electric trains, onboard computers automatically reports slippery areas to the control center.
Our dispatching staff use this data along with engineer reports to identify problem areas and proactively instruct trains to reduce speeds through them. On the subway, we instruct train operators to slow down when approaching stations in areas prone to leaf buildup. While these speed restrictions may cause minor delays, they ensure safety and minimizes the number of flat spots on wheels.
Finding and fixing damaged wheels quickly
We've installed a Wheel Impact Load Detector in the Metro-North Park Avenue Tunnel. This system monitors every wheel on each train for flat spots, and allows us to identify and prioritize wheels for repair.
We've also installed new high-capacity wheel truing machines in our shops at Croton-Harmon, New Haven, and West Side Yard. These machines repair damaged wheels faster and allow us to return cars to service sooner.