A number of years ago, configurable light-up signs were installed along major highways in Texas, such as I-35 here in Austin. Among other uses, they would display real-time information about traffic, in this format:
[ Name of up coming intersection ] [ X Minutes ]
FM 734 7 MINUTES
I noted at the time that the usability of this information was terrible. If I’m not a local, there’s a very good chance that I have no idea how far away the upcoming intersection is, and even if I am familiar with it, I have to estimate how far away that is and then do the math myself about how bad traffic is (A separate usability issue is that the signs use numerical designations for roadways, not necessarily the commonly used names. In the example above, FM 734 in Austin is also called Parmer Lane, and I doubt very many people know its numerical designation).
I was pleased to see that in the last year or so, the signs were changed to read:
[ Name of up coming intersection ] [ Y Miles ] [ X Minutes ]
FM 734 5 MILES 8 MINUTES
So, now a driver doesn’t need to know anything about the upcoming intersection; the miles and minutes are sufficient to understand the traffic flow. Somebody at the authority that manages these signs got the message and managed to make a change for the better. I guess they could have done the math for the drivers and added the average MPH, but this change is sufficient, I think.
Now if someone would only make it clearer at the upper/lower-deck split of I-35 in downtown Austin that both options will get you through Austin, my life would be complete. As it is, every day there are many drivers switching lanes at the very last second, presumably because it’s not clear to people driving through Austin that both options merge back up in a few miles.