Sometimes, when trains have been reduced in length and when things are getting crowded, train guards allow second-class passengers to move to first class to spread the burden. However, this is rather exceptional and normally, your second-class ticket cannot be used in first class. But apparently, this is not a problem for an increasing number of passengers. Things could be worse though, as some are travelling without any kind of valid ticket. Their number dropped substantially in 2012 to 2,439 coming from 5,967 the year before that.