Note that there is a one hour time difference between Lithuania and Poland
(Šeštokai -) Mockava LG - Trakiszki PKP (- Suwałki)
[D] Services had been withdrawn whilst the "Rail Baltica" project work was underway, extending the standard gauge tracks initially to Kaunas. Previously PKP worked to Šeštokai on standard gauge tracks, which are interlaced with broad gauge [1520 mm] from Mockava, on one daytime train pair from Warszawa to Suwałki and Šeštokai, with connections from/to Kaunas. There is a "SUW2000" gauge changing system at Mockava but this was used only by the overnight passenger train pair which was withdrawn after 28 May 2005 and replaced by a road service, which itself was withdrawn in 2012.
A two pair weekend plus Northbound on Fridays, southbound on Mondays passenger service between Białystok and Kaunas commenced on 17 June 2016 operated by PKP DMU's.