For those of you considering heading to Merida or Valladolid via Coba and Chemax, I had the opportunity to drive that highway just yesterday and I can tell you that the portion from Tulum to Cobá has improved mightily and that it is regulation-wide and not a pot-hole in sight. Sweet relief!
However, once you go around the traffic circle that divides the highway into the Coba turn-off and the continuing highway to Chemax/Valladolid, beware. There is construction immediately in the form of an unpaved stretch of bumpiness; not much however.
Then it gets much worse. Although there is evidence of road-widening work in progress, the actual two lanes remaining are paved as if a space ship had dropped asphalt blobs from way up high. Veeery bumpy and veeery narrow. Be very very careful here. (short video below)
This goes on for a while until you see the sign 'Welcome to Yucatan' and the highway gets much better, fast. Smooth and wide, the only thing missing for some stretch of it is actual lanes painted but that is coming as you will see when you get closer to the junction with highway 180 (free) that runs between Cancun and Mérida. Turn left at this junction for Valladolid and Merida.