Since 2011, six out of eight NJ Transit lines, including the Northeast Corridor, have seen their performance rates decline.
The Northeast Corridor commuter trains are the most frequently late, and more of them are arriving later.
The rail on-time performance data, found in NJ Transit annual reports, calculates the percentage of trains that arrive on-time to their destination. It shows the NEC has had the lowest percentage of on-time trains every year for the past five years.
It's been getting worse, falling to a low of 89.9 percent on-time in 2015 after reaching a five year high in 2013 of 94.4 percent.
The Northeast Corridor line has the highest ridership of all NJ Transit lines with 121,950 boardings on the average weekday in 2015. The line runs from Trenton, cuts through Middlesex and Union counties, passes through Newark Penn Station and ends at New York Penn Station.
It also shares rail space with Amtrak, which may be one reason NJ Transit trains that pass through are likely late more often, since Amtrak gives its own trains priority.
In fact, the line with the second-lowest on-time trains is the North Jersey Coast Line, which also partly shares rails with Amtrak.
Other trains lines have fared better. Over the last five years, Main/Bergen, Morris & Essex, Pascack Valley and Raritan lines' on-time performances have never dipped below 93 percent.
The Montclair-Boonton line rose to 96.4 percent on-time in 2013 before dipping in 2014, and finishing off with 93.1 percent performance in 2015. Morris & Essex improved a little in 2015 after dropping in 2014 to 93.1 percent, from 95.8 percent in 2013.
Then there's Atlantic City line's on-time performance, which has been consistently falling every year from a high of 96.7 percent in 2011, to 92.8 percent in 2015.
A train is considered late if it arrives to its final destination six minutes after its scheduled time.
These performance measures are in fiscal years, which for NJ Transit starts July 1 and goes through June 30.
Another possible reason for the falling on-time performance measures could be the rise in mechanical failures of trains throughout the NJ Transit system.
In 2014, mechanical failures in NJ Transit raise reached a four-year high of 533 in 2014-- almost double the number reported by the Long Island Railroad and the Metro-North.
It's also worth pointing out that these performance measures take into account only destination.
Carla Astudillo may be reached at castudillo@njadvancemedia.com. Follow him on Twitter @carla_astudi. Find her on Facebook.