I am not going to be using streets as the main layout of the map, but I have ways around it.
Sightline barriers include:
Cars, Buses, Supports for elevated trains, fire escapes with sheetmetal on the bottom, bookstand props from the soho pack, concrete barriers, police barriers, open doors, floating staircases, and signs.
When you work with a city, you aren't restricted to flat landscapes when doing level design. Something I remember most from the videogame: "The Last of Us" (a game I take a lot of inspiration from), was that the city levels never consisted of flat, open, boring areas stuffed with ruined cars and dumpsters just to make it feel less open. In fact, there was a lot of split level buildings, underground areas, sunken streets, shared basements, suspended walkways, etc.
Long before I started blocking out buildings I kept this all in mind, and I have a folder of 200+ reference images of cities such as New York City NY, Albany NY, Buffalo NY, Rochester NY, Boston MA, Chicago IL, and other big industrial cities that were highly populated during the 1960s.