Two More Trip Pictures - One With A Question

Some worried about road conditions while we were on our recent trip.  In truth, the roads were mostly fine.  We hit a few snow flurries, but nothing heavy in terms of new snowfall.  Worse, though, was blowing snow, particularly in Wyoming.  Anne drew the short straw for the worst case of blowing snow.  The picture below shows a mild case of what we were dealing with... 45 MPH wind gusts and a fair amount of snow can make for an awful mess on the road.  As I say, though, this picture is a less severe instance of the problem:

This next picture leads to a question I've had for something like 15 years, since the first time we did this drive:

 

What are those groups of three marks in the right lane?  They span what might be expansion joints in the pavement, and each group of three appears roughly where the tires of vehicles in that lane would be.  I only see these in Wyoming and a bit in Nebraska.  Just once this trip I saw a similar things with groups of four similar marks.

I haven't been able to figure out what these marks are for, but they've been on I80 in Wyoming for a long time.  If anyone knows, please drop me an email and explain it to me.  Thanks!