While the prevailing assumption is that "livable" street treatments such as street trees, on-street parking, narrower lanes, and adjacent roadside development have a negative impact on transportation safety; empirical evidence indicates that these designs are actually safer than conventional roadway designs. In analyzing crash data for several livable and comparable sections of roadway, livable sections had fewer fixed-object, multiple vehicle, and pedestrian crashes as well as fewer injuries and fatalities.
Dumbaugh, Eric. (2005). Safe Streets, Livable Streets. Journal of the American Planning Association 71(3), 283-300.