The phrase "principal streets" refers to the main roads or highways within a city or town. These streets are usually the busiest and most important ones, connecting various areas and allowing for easy transportation. Full definition
The festival will climax with street carnivals on principal streets in the area, which are expected to last over night. (citifmonline.com)
``... immediately, they should get their tools together and march into town on principal streets so that public confidence will be restored in them,» he added. (ghtvonline.com)
The demonstrators who took off from the school's campus, passed through various principal streets... (citifmonline.com)