1. A method performed by a road segment determining system for identifying beforehand a situation with a potentially in-alert driver of a vehicle, the method comprising: determining a position of the vehicle; determining pre-stored road characteristics of a road segment assumed or known to be ahead of the vehicle, wherein the pre-stored road characteristics comprise geo-tagged driver behavior data parameters that indicate characteristics of driver behavior associated with the road segment for a plurality of vehicles having previously been driven along the road segment; and determining whether or not the road segment is monotonous based on comparing at least a first geo-tagged driver behavior data parameter of the pre-stored road characteristics with predetermined monotonous road criteria comprising preferences for geo-tagged driver behavior data, the predetermined monotonous road criteria referring to preferences making up the criteria for under what circumstances a road section is considered to be monotonous.