[okie01]

I don't think so. I-30 ends west of Fort Worth when it runs into 20. Then 20 ends in west Texas between Pecos and Van Horn. The milepost at Texarkana should be in the 220-230 mile range

I believe, if you went to Texarkana, you'd find that the mileposts on I-30 read the distance from El Paso (the New Mexico border, actually). And so does the milepost on I-20 at the Louisiana border.

[PAR35]

Then you believe wrong.

Exits in Texas match the mileposts. The first exit in Texarkana is Exit 222. https://www.google.com/maps/@33.4703604,-94.0448224,3a,75y,233.29h,77.79t/data=!3m6!1e1!3m4!1s0DoNshgoxAUWbPGiqwuUSg!2e0!7i13312!8i6656!6m1!1e1

First Milepost I spotted 223. https://www.google.com/maps/@33.4698619,-94.0538365,3a,75y,268.28h,83.16t/data=!3m6!1e1!3m4!1snhfOrZjHH8GbD8bjV2dXYw!2e0!7i13312!8i6656!6m1!1e1