17. The system of claim 16 , wherein the model storage partitions values of disfavor into separate data buckets by explicit conditions, and wherein the attribute model learning module forms a conditional variant model for each respective explicit condition based on the values of disfavor in that bucket.
16. A system for generating attribute models for use in a navigation system in a vehicle, the method comprising: an attribute model learning module that, for each of a plurality of driving sessions, during which the user travelled over a plurality of road segments in the vehicle: receives sensor data of the vehicle for each of the plurality road segments travelled during a driving session; and associates the sensor data with at least one of a plurality of conditions, each condition descriptive of the driving session at the time the user travelled on the road segment; a disfavored route modeler that, for each of the plurality of road segments, determines a value of disfavor of the road segment based upon the sensor data collected for that road segment, and associated with at least one of the conditions; and a model storage that, for each of the plurality of conditions, stores the values of disfavor in a conditional variant model associated with the condition.