> (b) An operator of a vehicle on a roadway moving more slowly than the normal speed of other vehicles at the time and place under the existing conditions shall drive in the right-hand lane available for vehicles, or as close as practicable to the right-hand curb or edge of the roadway, unless the operator is:

> (1) passing another vehicle; or

> (2) preparing for a left turn at an intersection or into a private road or driveway.

https://tcss.legis.texas.gov/resources/TN/pdf/TN.545.pdf#545

Note this law specifically mentions "normal speed of other vehicles at the time and place" and doesn't directly mention speed limits. So by the text of this law, if you're driving the speed limit and hanging out in the left lane while the normal speed at that time is like 10 over you're technically breaking this law.

We have specific signage for highways where this is supposed to be the law.

https://www.txdot.gov/manuals/trf/smk/regulatory_signs/left_...