The other way to look at this is that the requirement is there for all operators of all conveyances to report and for the passengers as well to self-declare illness at the border. This advance reporting requirement is an additional practical measure so we can make the best possible arrangements for people arriving by air and marine transport in advance of their arrival to make the necessary arrangements for the appropriate follow-up so they can get the best medical attention.
The problem, to be honest with you, if you want to get into the whole issue of land conveyances, is, as I've said, in many practical senses it's not possible. For example, there are multiple bus operators all around North America. To talk about all the types of routes and points where they could cross, you would then have to have multiple phone numbers for them to contact in advance, and then what exactly would they be reporting? The most common type of illness most people would have would be something like a cold or a respiratory illness. Can you imagine a busload of folks where the bus operator would be reporting or trying to contact a border official because some of the people have a cold?
Then what happens is that people may be standing up, we might get the whole system activated, and then before they even arrive their condition worsens and they disembark and get to a local hospital. So the people at the border might be waiting for someone who never arrives because they're actually practically managed even before they get to the border.