Autumn leaves bring another issue that could cause Metro-North delays this season.

It’s called the “slip-slide” condition that is caused by a slimy substance left by crushed leaves on the rails that gets even more slippery after it rains.

“When a train attempts to speed up or slow down, this gelatinous slime can cause the wheels to slip or slide along the rails.” Metro-North says.

“In severe cases, the train will automatically make an emergency stop, because the on-board computer system perceives ‘slip-sliding’ as the train not slowing down when it should. And this slip-sliding during braking also creates flat spots on the train's wheels, forcing us to take much-needed equipment out of service for repairs.”

Among other measures Metro-North does to deal with “slip-slide” conditions include:

Using two large high pressure rail washers and several smaller rail scrubbers to remove crushed leaf slime from the tracks.

On-board sanders on diesel trains automatically drop sand on the tracks to help improve traction and reduce wheel slippage when it begins to occur.

Instructing engineers to report slippery conditions to the Metro-North Operations Control Center

Enhancing its computerized train-tracking system to allow for automatic reporting of slip-slide incidents and conditions, enabling corrective action more quickly.

Installing a wheel impact load detector across all four tracks in the Park Avenue Tunnel near Grand Central Station. This monitors for wheel flats that may have developed during operation and allows Metro-North to identify and prioritize wheels for repair.

During extreme slip-slide conditions, train speeds are reduced for safety and to prevent wheel damage.

“While we can reduce the incidents of slippery rail, we cannot eliminate them,” Metro-North says. “We will continue our efforts to minimize any delays and canceled trains due to slip-slide.”

Slip-slide conditions are possible Friday night into Saturday with up to an inch of rain expected, according to the National Weather Service forecast.