An approach is provided for detecting a presence of a physical divider on a road segment. The approach, for example, involves determining a number of positive observations of the physical divider on the road segment based on sensor data collected from one or more vehicles traveling the road segment. The approach also involves determining a number of negative observations of the physical divider on the road segment based on the sensor data. The approach further involves calculating a probability of the presence of the physical divider based on the number of the positive observations and the number of the negative observations. The approach further involves updating map data for the road segment to indicate the presence of the physical divider based on determining that the probability of the presence of the physical divider is greater than a threshold value.