@jon the only trains with compulsory reservations are IC trains using ED161 (going onto bocznica.eu and typing in ED161 will show all of them, but most of them are on the Wrocław-Łódź-Warsaw-Bialystok/Lublin and Bydgoszcz-Warsaw lines) as well as EIP trains, so you can actually just hop in, you also don't actually need a reservation for EIC.