I must say that nowadays similar situation you may observe in London too - throughout central London you may see construction/road works on main streets... Understandably, in both capitals, this creates significant inconvenience for people who live or work there, tourists and motorists. I cannot comment on differences in quality of construction/road works between Yerevan and London, since have no insight into the issue. However, when I said that there is "similar situation" in London, I was mainly referring to the fact of works taking place.
Below are my London pictures. Compare them to the pictures taken by Onnik Krikorian in Yerevan streets, and you will note one big difference. In Yerevan, as Onnik rightly pointed out, "building materials and debris left lying around have made a three or four minute journey a safety hazard for pedestrians and motorists alike." In London, all construction works are isolated by special road work barriers. Relatively simple thing to do, which will make Yerevan roads safer.
*source of Yerevan pictures - Onnik Krikorian/Oneworld Multimedia