Japanese travelers are crowding highways, train stations and airports as they head to their hometowns and leisure spots for the annual "bon" holidays.
The Japan Road Traffic Information Center says at 11 AM on Saturday, outbound traffic on the Tohoku Expressway was backed up for 36 kilometers around the Hanyu parking area in Saitama Prefecture.
It says there is also heavy congestion on the Kan-etsu Expressway and Kyushu Expressway.
The congestion in some places is expected to continue until Saturday evening.
Japan Railways Group companies say occupancy for non-reserved seats on one Shinkansen bullet train service from Nagoya to Hakata was 170 percent, and another from Tokyo to Hakata 130 percent.
Reserved seating on outbound trains on the Hokkaido Shinkansen line is nearly fully booked throughout the day.
Amid the congestion, an electricity blackout forced an inbound train on the Tohoku Shinkansen line to stop temporarily in the northeastern prefecture of Miyagi.
East Japan Railway Company suspended services between Sendai Station and Morioka Station in Iwate Prefecture, but resumed operations at 8:20 AM after power was restored.
Some routes for domestic flights out of Tokyo and Osaka on Saturday are fully booked, including those headed to the southern prefecture of Okinawa.