Japan is a long-shaped country, so highways carry a huge burden taking people between hometowns and big cities like Tokyo, whenever there is a long break.

One reason is that around half of the vehicles still pay manually at toll gates, instead of using the wireless devices that process the payment as you pass the gate. Even when using them, traffic slows down because cars slow down passing the narrower toll gates.

A few extra highways are being built at some places to reduce congestion. However, widening exits and expressways is not a popular choice at this point because of the declining population.

I don't recommend traveling on expressways at either end of a long vacation. Trains are more reliable and convenient.