Around 3,500 employees - engineers, electricians and signalmen - have gone on strike after employers and unions failed to agree on new wages. Months of negotiations ended on Friday evening, according to union representatives.
The LIRR trains - operated by the state-run Metropolitan Transportation Authority (MTA) - are essential for tens of thousands of people who live on Long Island but work in Manhattan. They are also popular for trips to Long Island beaches.
On a typical weekday, LIRR trains carry around 300,000 passenger trips.
The MTA will deploy extra buses to handle some of the traffic.
