This Ralph Blumenthal/NY Times article does a good job of summarizing the massive scale that is the proposed Trans-Texas Corridor project:

. . . the Trans-Texas Corridor, a public-private partnership unrivaled in the stateís ó or probably any stateís ó history, that would stretch well into the century and, if completed in full, end up costing around $200 billion. [. . .]
The plan envisions a 4,000-mile network of new toll roads, with car and truck lanes, rail lines, and pipeline and utilities zones, to bypass congested cities and speed freight to and from Mexico. [. . .]
The corridor project grew out of the 2002 governorís race when [Governor] Rick Perry, . . . surprised transportation experts by taking ideas they had discussed a decade earlier, to little interest, and ìsupersizing them,î as one recalled.
The project grew to consist of four ìpriority segments:î new multimodal toll roads up to 1,200 feet wide paralleling Interstates 35 and 37 from Denison in North Texas to the Rio Grande Valley; a proposed I-69 from Texarkana to Houston and Laredo; I-45 from Dallas-Fort Worth to Houston; and I-10 from El Paso to Orange on the Louisiana border. But the exact routes are years away from being designated.