I think the greater significance of this is that human travel ... obeys some quite simple, independent rules.

There are some universal rules governing human travel and they can be used to develop a new class of model for the spread of infectious disease.

There are some universal rules governing human travel and they can be used to develop a new class of model for the spread of infectious disease.

If you want to understand how disease spreads, you need to understand how humans travel, because a lot of the time humans carry the disease from one place to the next. It's clear people travel long distances less often, but make a lot of short trips, but what are the details? How often are trips of a certain distance made?

This is a very good estimate of how humans travel.

This is a very good estimate of how humans travel.