15. A method for generating attribute models for use in a navigation system, the process comprising: computing a value for each desired attribute along one or more road segments covered by each driving session for a user; computing a default value for unseen road segments not yet traveled; and forming one or more attribute models for each attribute based on the corresponding attribute values.
15. A method for generating attribute models for use in a navigation system, the process comprising: computing a value for each desired attribute along one or more road segments covered by each driving session for a user; computing a default value for unseen road segments not yet traveled; and forming one or more attribute models for each attribute based on the corresponding attribute values. 26. The method of claim 15 wherein at least one of the one or more attribute models provides a summary statistic of attribute values that have been observed during driving sessions on a particular segment.