One indicator of pavement condition is the smoothness of the ride. This measure gets to the subjective "feel"
of the roads that most of us notice when we’re riding on the road. Although this can vary by season, due to
Iowa’s climate roads are typically rougher in the winter, the measure of smoothness is one indicator of the
overall pavement health – particularly when combined with measures of pavement structure.
All states use a federally mandated standard measure of pavement smoothness, the International Roughness
Index (IRI). The map below classifies each of Iowa’s primary routes as good, fair, or poor based on
pavement smoothness. It is important to note that this is only one indicator of overall pavement condition
and many other factors are also taken into consideration when determining which roads are candidates for
Pavement smoothness for all primary highways in Iowa (numbered interstate, U.S., and Iowa routes).