score:3
As far as I know, due to the major infrastructure work (for high speed trains) train schedules from Istanbul to the rest of Turkey are cancelled. I am not completely sure, so be advised.
If I were you, I'd take a bus from the city center, as the tickets are very cheap and, relative to trains, buses are more comfortable and faster.
You can have a look at the following sites:
www.pamukkale.com.tr
www.kamilkoc.com.tr
www.obilet.com
As it's a short distance, I am pretty sure you can easily obtain a ticket at the last minute. All bus companies have shuttle buses that take you from the point of ticket sale to the transfer hub, where you start your journey. Those shuttles are free of charge.
Bus tickets should be around 20 Turkish Lira.
Hope I could help.
Upvote:0
I have just check it online and seen that you can take the train but the only departure location in Istanbul seems Pendik (in Asian Side). It might be difficult for you.
As mentioned before, bus is a good alternative solution. Or, there is a company called blablacar.com. If you are not more than 4 I think, you can check the website and find a guy with a private car who can take you to Izmit. It is cheaper than bus tickets. I think you only share the cost of gasoline. I have never used it but heard a lot. You may want to take a look.