I suspect half speed is actually a rational decision given some underlying model AnnaSalamon was not aware of explicitly.
For instance, she may intuitively feel that she just passed the hotel. If so, then being extra careful to look well for features and marks around you that could give you hints of whether this happened could work best at half speed. Are there fewer hotels around? Is it a residential area? Does the amount of economic activity seems to be increasing or decreasing as I move in this direction? Then, you can turn around and get there faster.
Formalizing the precise model that would make half-speed the rational choice may be a bit complicated. But that's what the Bayesian approach to cognitive sciences would try to do first.
Related to: Half-assing it with everything you've got; Wasted motion; Say it Loud.
Once upon a time (true story), I was on my way to a hotel in a new city. I knew the hotel was many miles down this long, branchless road. So I drove for a long while.
After a while, I began to worry I had passed the hotel.
So, instead of proceeding at 60 miles per hour the way I had been, I continued in the same direction for several more minutes at 30 miles per hour, wondering if I should keep going or turn around.