In November 1980, the number of inhabitants of Vilnius exceeded 500,000. Because of shortage of housing for a growing population of the city, large scale Microdistricts (so-called ''sleeping districts'') were built in the elderates of Antakalnis, Žirmūnai, Lazdynai, Karoliniškės, Viršuliškės, Baltupiai, Justiniškės, Pašilaičiai, Fabijoniškės and on a smaller scale in other parts of Vilnius. These were connected with the central part as well as with industrial areas via expressway-like streets (so-called ''fast traffic streets'') and by public transport, noticeably extensive network of trolleybuses (from 1956).