Here is the explanation provided by the MTA regarding the Tuesday morning delays on Metro-North Railroad.
"The average delays of 10-15 minutes you may have experienced during this morning's commute resulted from an extreme case of "slippery rail," which is created by a slimy substance left by crushed leaves on our rails that gets even more slippery and slimy after it rains.
"This gelatinous “slime” can cause the wheels to slip or slide along the rails as a train tries to speed up or slow down. In severe cases a train will automatically make an emergency stop, because the on-board computer system perceives “slip-sliding” as excessive speed.
"This morning we were experiencing slippery rail across all main and branch lines. Due to the severe condition, and to prevent damage to our equipment, during the height of our AM Peak service, we put into effect a weather restriction that reduced speeds throughout the entire railroad.
"While this resulted in some delays to your service, it ensured safe operation of our trains and also prevented a greater delay because of wheel damage. And keeping our train wheels in sound working condition also means we can operate at regular speeds in non-problem areas, and we don't need to take the equipment out of service to maintain it.
"Slippery rail is a recurring problem at this time every year. While we have been able to somewhat reduce its impact on our service, we cannot entirely eliminate it. For more information on the proactive measures we take to combat slippery rail, see http://www.mta.info//mnr/html/slipslide.htm .
"We will continue our efforts to try to minimize any delays and inconvenience slippery rail may create for you this autumn.
"We regret any inconvenience you may have experienced as a result of this morning's delays. As always, we appreciate your patience."