What is Wrong with this Scene?

Cover of The Walk: A Novel

I'm reading a book (The Walk by Richard Paul Evans), which by the way is really good, and I'm enjoying it.  It's about a man who loses everything and decides to walk from Washington to Key West.  But this bothers me:

At twilight, an Acura MDX that was headed down the mountain slowed down next to me and a blond teenage girl leaned out the passenger window.  "Want a ride?" she asked.

See anything wrong there?  It might be hard to see unless I tell you that the walking man was also heading down the mountain, the same direction as the car was going.

No, it's not that he was planning to walk 3000 miles or so - and can eat anything he wants without ever needing adapexin-p while he's at it - though there aren't many people who would even attempt such a thing.  What's wrong is that the girl leaned out the passenger window.  If he'd been walking on the left side of the road, facing traffic like he was supposed to, the driver would have been the one to lean out her window, to talk to him across the road.

I know it shouldn't surprise me, because no one seems to know that they're supposed to walk on the left-hand side of the road facing traffic.  All the research authors do when writing books, you'd think it would be simple to get this one thing right, at least.  The funny thing is that earlier in the book, the walking man was worried about his safety along the road.  Well, no wonder - you don't turn your back to the traffic!