Comment by gregatragenet3

IMO these findings that roads are safer without markings, or by being narrower are because drivers have a heightened level of attention and focus when they encounter something unexpected. When they are widespread and commonplace the accident rate will go past that of wide/marked roads. For a fair comparison, if you compared a country with wide/marked streets to a country where narrow/unmarked streets are commonplace (Mexico for example) you'd find marked/wide is much safer.