A driving safety support system according to one aspect of the present disclosure includes a server, and a safety driving assistant device. The server performs operations including: acquiring, from probe vehicles, probe information including information of a time within a predetermined time period and a position of the corresponding probe vehicle at the time; calculating, based on the probe information, a traffic congestion tail position located upstream of a branch point at which a road branches into a plurality of lanes; and calculating a lane-change recommendation section in which a lane change is recommended based on the traffic congestion tail position. The safety driving assistant device performs operations including executing a driving safety support process for a target vehicle based on the lane-change recommendation section.