The first section of the Long Island Rail Road's double track is being installed in Ronkonkoma.
Currently, there is only one track between Farmingdale and Ronkonkoma. This means if a train becomes disabled, there is no alternative route and that has caused major delays.
The second track going in today will stretch 18 miles along the busy stretch from Ronkonkoma to Farmingdale.
It is expected to be complete in 2019 and will provide half-hourly service during off-peak times and weekends.