Some organisations use 'as the crow flies' for distance calculations which can sometimes be useless. For example if you would accept applicants within a 20 mile radius from Southend-on-Sea this would include applicants from Sheerness:
No offence to people in Sheerness, but that would be a very long drive (62miles / 100 km).
Fortunately we calculate commuting distance, in this case knowing the applicant has to travel 100 miles, so can automatically exclude applicants that are not within a 20 mile commute.
Naturally you can set 20 miles, 57 miles or any other distance that is relevant to you.