[Data-Viz] The Sinuosity of Highways

We don’t always use highways, but when we do, we prefer sinuosity. 

Since we just got done talking about the meaning and importance of highways, we found it quite serendipitous to see this data visualization post on r/dataisbeautiful dedicated to the major highways of the United States.


Sinuosity is one of those words that, graphically, mirrors its meaning. It refers to the ability to bend or flex, and when used with regard to a road it really just means how bendy it is.

Several factors determine how sinuous a road or highway can be- natural features like mountains, rivers, coastlines or even political factors like borders can shape the way roads and highways connect one location to another. What the visualization above shows is the difference between the actual plotted interstate and the actual distance between its beginning and end. In the case of this graph, the distance “as the crow flies” between the beginning and end of the highway is the “geodesic” length.

Data scientist Seth Kadish, the author of the post and graph, explains his methodology and findings:

For this post, I’ve mapped the longest interstate highways in the continental USA alongside the geodesic between each highway’s endpoints. I then graphed the differences in distances, and the respective sinuosities. The sinuosity of a path is simply its length divided by the shortest distance between its endpoints.

From these data, we can see that north-south trending highways (odd numbered) tend to be less direct, though I-35 is a good exception to that rule. I-25 is both the shortest and most sinuous highway shown, bouncing east to avoid passing directly through the Rocky Mountains. And I-95, which isn’t quite continuous, can’t be blamed for straying from the direct route, given that most of it would need to be a bridge over the ocean.

Among the east-west highways shown, I-20 has the lowest sinuosity, while I-90, which dips south to avoid the Great Lakes and Canada, has the highest. Note that I-90 is the longest interstate highway in the USA, but its geodesic is actually shorter than that of I-80!

Given the long, endless stretches of straight desert nothingness on I-80 and I-40, we were surprised to find that I-20 had the most direct path in the US. Great news for all of you making the trip from Atlanta to Odessa.

Perhaps we’ll look into the average drive time for some of these routes- maybe the shape of the road has an impact on congestion.

For those of you interested, Seth used data from https://www.census.gov/geo/maps-data/data/tiger-line.html & http://www.fhwa.dot.gov/reports/routefinder/table1.cfm