Holidays transform transport in a predictable rhythm: the day or two before a major holiday, everything heading out of big cities is jammed as people travel to family, and the last day or two of the break, everything flows back in. Intercity trains, buses, and flights sell out early and cost more, highways clog, and in countries with huge festival migrations, like lunar new year in parts of Asia, tickets can vanish the moment booking opens.
Inside cities the picture inverts: streets often go quiet on the holiday itself, but tourist sites, parks, malls, and temples or churches connected to the festival get intensely crowded. Public transport typically runs reduced holiday timetables, so check schedules rather than assuming normal frequency.
Strategies that consistently work: travel on the holiday itself rather than the eve, when everyone else has already moved; book intercity tickets as far ahead as the system allows; visit major attractions at opening time; and consider doing the opposite of the crowd, enjoying the emptied city while residents are away. If you have flexibility, shifting your trip even one day off the peak makes a remarkable difference.