FAQs and other good comments from our readers:
1) How do you deal with trips at counties that touch the Canadian and Mexican borders?
In general, they are treated like any other trip (so, a trip that enters from Mexico will show up as external). However, the border crossing stations often cause vehicles to stop for an extended period of times, thereby "breaking" the trip. If the station is "internal" to the county, such a trip will end inside the county in our database, which could skew results towards internal trips.
2) What about very large counties that people just drive through? Wouldn't they have high passing through counts?
They absolutely could. The full county table will contain all that information. We do have a table with the ratio of area to each trip type for those who are interested (use the contact us form to ask!)