I-14 Expansion and Improvement Act of 2018 This bill amends the Intermodal Surface Transportation Efficiency Act of 1991 to include additional routes within The Central Texas Corridor, a high priority corridor on the National Highway System, and to include The Central Louisiana Corridor and The Central Mississippi Corridor as high priority corridors on such system. The bill extends the Central Texas Corridor eastward following highways LA 8, LA 28, and US 84 in Louisiana through Leesville, Fort Polk, Alexandria, Pineville and Vidalia, where it would cross the Mississippi River.