1. A method, comprising: performing by one or more computers: determining respective values of transit characteristics from a source location to a plurality of destination locations, wherein the plurality of destination locations define a macro region; dividing the macro region into a first plurality of regions; performing splitting of one or more regions of the first plurality of regions to create additional regions and expanding at least one of the first plurality of regions to form a new region, wherein said splitting and expanding is performed a plurality of times to generate a plurality of possible sets of regions, wherein each set of the plurality of possible sets comprises a different plurality of divisions of regions of the macro region; evaluating each set of possible regions using a fitness function, wherein said evaluating comprises applying the fitness function to each region of the set of possible regions to produce a fitness score, wherein the fitness function takes the respective values of transit characteristics for each region as input; selecting a set of regions for the macro area based on said evaluating, wherein the selected set of regions has a best fitness score based on the evaluation of the sets of possible regions; and determining a regional value of a transit characteristic for at least one region of the selected set of regions, wherein the regional value provides a common transit characteristic value for each of multiple destinations within the respective region.