Speed profile dictionary

A speed profile dictionary and associated lookup tables are disclosed, A set of distinct speed profiles is defined using a statistical analysis routine. Preferably, the statistical analysis routine uses clustering. The speed profiles are then matched to locations codes identifying physical locations on a road network and days of the week. Applications using historic traffic data may use the speed profile dictionary and one or more lookup tables instead of a complete historic traffic database, thereby reducing the amount of memory needed to store historic traffic data.