What is the best way to find the halfway point (in driving time) between two cities?

I have to plan a road trip for the family. We’re taking my mother in law half-way to her sister, and her sister will meet us at the halfway mark.

We’d like to make the driving distance and time as equal as possible.

In miles, the halfway point between Tampa and Danville, Illinois appears to be Chattanooga, TN, but is that accurate for drive time as well? Is there an online tool to figure that out?