Koleje Mazowieckie is the first railway carrier in oland owned by a local authority. The company was established on 29 th July 2004 by Mazowsze Region Authority (Samorząd Województwa Mazowieckiego) and „PKP Przewozy Regionalne” sp. z o.o. On 8 th January 2008 the Mazowsze Region Authority became the sole shareholder of Koleje Mazowieckie.
Since its establishment Koleje Mazowieckie has consistently implemented a program designed to organize a railway transport system which would fulfill needs of residents of Mazowsze Region. The services quality improvement process initiated by setting of a proprietary transport tariff and a periodic time schedule included reactivation of suspended railway lines, introduction of the offer „Wspólny Bilet ZTM – KM” (integrated municipal bus and railway tickets) and purchase of a modern rolling stock.
In 2005–2009 Koleje Mazowieckie reactivated numerous, suspended railway lines. Currently passengers can enjoy railway lines Nasielsk–Sierpc, Kutno–Płock, Warszawa–Góra Kalwaria and many more.
In addition, works on introduction of the integrated offer „Wspólny Bilet ZTM – KM” commenced in 2005. The offer is designed to allow residents of Warsaw urban area to use trains operated by Koleje Mazowieckie and municipal transport system with a single ticket.
For several years, passengers of Koleje Mazowieckie can also travel by modern rolling stock: electric traction units EN75 Flirt or EN76 ELF, railway buses SA135 and the double-decker „push-pull” carriages supported by a locomotive TRAXX P160 DC.
The strategy of Koleje Mazowieckie resulted in a significant increase of a number of passengers from 40 million in 2005 to over 59 million in 2012. With that result Koleje Mazowieckie take second position among rail carriers in Poland.