Amtrak will replace concrete railroad ties on Track 1 into New York between Metropark and Rahway. The ties are being replaced to avoid speed restrictions.
Amtrak and NJ Transit trains will have three tracks available instead of four until the work is finished on Aug. 30.
Riders on NJ Transit's North Jersey Coast, Northeast Corridor, Midtown Direct and Raritan Valley lines may experience delays of up to 10 minutes.
The expected delays come after 12 incidents in July led to major service disruptions for NJ Transit train passengers. On time performance for NJ Transit trains in July was at its worst level since December 2007.