Abstract: A method of planning optimum routes on the basis of successively selected sub-sets of the total topographical and traffic information, so-called buckets, which method anticipates which buckets will be of importance in the near future for the calculation of the navigation data, and navigation system comprising a route planner for carrying out such a method.

Abstract: A route planner comprises a control unit, a working memory and a storage memory in which a topological road network is stored in the form of at least one n-cell table. For the planning of a route between a starting point and a destination point a set of candidate cells is searched each time on the basis of an expansion index which indicates and n-cell, a further expansion index being derived from said set of candidate cells. For the storage of information blocks for each of the candidate cells found, a memory location is reserved in the memory working memory for each n-cell associated with an n-cell table used for the planning of the route. The information block of a candidate cell comprises inter alia the expansion index used to find the candidate cell and is stored at the memory location reserved for the relevant candidate cell. The sequence of the reserved memory locations preferably correspond to the sequence used to represent the n-cells in the table.