Dylan Reinhardt <zope@dylanreinhardt.com> wrote, in part:

But if the purpose of this is to get some proxy for driving distance, there's no compelling reason to be any more accurate than within a mile or so... distance "as the crow flies" is only a bare approximation of driving distance anyway.

Beyond what I wrote in a previous message: It just occurred to me that driving distances can be outside the bounds given by the L(1) and L(2) distances because of obstructions, political boundaries, etc. For example, for those familiar with southern Ontario, the road distance within Canada between Niagara Falls and Oshawa is greater than the L(1) distance since, to remain within Canada, one must drive around the western end of Lake Ontario.