What's the point of having it public then? The department of transportation is already using that data for monitoring traffic so there's zero need for anyone else to replicate their work. The value in making that data public isn't so that Joe Average can track traffic volume over time just like the DoT is already doing. It's for transparency and so that the public can find new and innovative uses for the information our tax money is already being spent on gathering.
There's no point if we're not allowed to use that data in new ways and we don't need the kind of "transparency" that only applies as long as the public isn't looking.
If a specific use is actually dangerous then that can be dealt with on a case by case basis, and it's arguable that they were right to send a cease and desist letter to this website, but making the data itself unavailable over it would be an overreaction