Highway
Motorway
noun
A street road is as wide as a street plus a road combined together. So cool! So wide! It's a highway!
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well. It uses the かい reading (not the がい) because it's at the beginning of the word.
東海道、中山道、日光街道、甲州街道、奥州街道は、五街道と呼ばれ、江戸時代の五大陸上交通路であった。
Tokai-do Road, Nakasen-do Road, Nikko-kaido Road, Koshu-kaido Road, and Oshu-kaido Road are called Gokaido, which were the five principal routes used during the Edo period.