As I’m sure most of you know, today is 4/20 and the number 420 has certain meaning in certain walks of life. Now, I’m not going to comment on the legality of marijuana but I did find something the pertains to engineering on this topic.

I-70, the major east-west corridor through Colorado is close to 450 miles long. This means that somewhere along the highway (out near Kansas) there should be a mile marker 420 but there isn’t. As you travel along, you’ll see mile marker 419 and mile marker 421 but no mile marker 420. Why? Well, I can only assume that CDOT (Colorado Department of Transportation) has had issues with that particular mile marker disappearing. You will, however see a mile marker 419.9! One of these days, I’m going to pull over and put a little line over the 9 to indicate it is a repeating number as 419.999… is exactly the same as 420.

p.s. On the same highway, there is also a mile marker 68.9…