Experience tells us that many libres (free roads) in Mexico have been being rebuilt in recent years - widened and resurfaced. A couple examples . . .
MX-110 and MX-90 between 15D and 45D - Yurecuaro - Penjamo - Irapuato - almost all new - wider - better surface .
Almost all roads in/out of San Miguel de Allende to/from - Queretaro - Dolores Hidalgo - Celaya
We used to pay a very high toll between 15D and 45D on 43D north of Morelia. Now the upgraded libres mean we have a cheaper route that is actually shorter and faster too.
Going south from Zapopan/Guadalajara toward Mazamitla they have almost completed the rebuilding of 15 - then from 15 to 110 on the unnumbered road between Tuxcueca and Mazamitla is all new.
Roads are being repaired and upgraded all over Mexico. Maybe readers here will post as we learn new and better routes.
With new and better roads - including all the new toll roads - it is getting easier to get around in Mexico every year.