Greetings Google Researchers.   Here is another of my "just curious"
questions.   When driving down the interstate highways in Washington
State I have noticed, usually in just one of the multiple lanes, a
patchwork of rectangular repairs in concrete surfaces.   These little
rectangles are 3 abreast a few inches apart in each of what might be
called the main wheel lines for vehicles.   The rectangles repeat
every few feet down the road and may go on for miles.   The rectangles
are about the size of a dollar bill.  So, imagine 3 bills slightly
apart ahead of the right front tire, then another 3 bills slightly
ahead of the left front tire, and then this pattern continuing every
few feet ahead.  The appearance is that the concrete has been bored
out and a new substance has been pored in.   I am curious about what
the highway maintainers are trying to accomplish with this and why
they only do this in one lane (usually the right lane).    In some
way, it must improve the life of the road, and I would like to know
how.

An awesome question!

I am a highway engineer, but not in Washington, but with friends at
the Washington DOT.  What you described could be several things: a
core drilled out of the pavement to inspect it, small patches to
repair spalling, skid resistance additives, or even dowel retrofits. 
If you are truly interested in finding out what that is, feel free to
email me at tim_baxendale@hotmail.com, and I can look it up for you.

cheers/bax

For baxendale-ga:   Hello Tim!   Thank you for your comment on my
question.   I would not want to ask you to go to any special trouble
to find an answer for me but I sure appreciate your offer to do so.  
It is interesting to consider that it may be a safety improvement to
reduce skidding.  It makes sense because these "repairs" are usually
in the lanes which have had the most traffic and show heavy use of the
surface.    I would welcome more comments if you are able to easily
obtain some more information. Best regards, seattle.

Seattle,

No schweat.  Please email me and tell me on which highway (I-5?) and
where you saw it, and I will try to get the info.

cheers/bax