The HDC was originally proposed in the 1970s as a metropolitan by-pass for trucks to alleviate truck traffic in the Los Angeles Basin and to facilitate truck movement from Mexico to points north and east. In 2004, the Metro Board adopted the North County Combined Highway Corridor Study that recommended strategies for addressing the high volume of truck traffic traveling on the I-5, SR-14 and SR-138 Freeways. The HDC was one of the preferred strategy improvements for some of the following reasons:
- The High Desert communities in the northern Los Angeles and San Bernardino Counties are some of the fastest growing subregions in Southern California
- Both counties had experienced tremendous growth and demographic changes in the last 20 years
- The rapid growth had caused travel demands to exceed roadway capacity resulting in deteriorating east-west travel speeds along the SR-138, which was primarily a two-lane highway.
In late 2010, the California Department of Transportation (Caltrans) and the Los Angeles County Metropolitan Transportation Authority (Metro) partner agencies initiated the HDC Environmental Impact Statement/Report (EIS/EIR) and released the Draft EIS/EIR for public review and comment in late 2014. Metro and Caltrans studied five functional alternatives and four physical variations in the Draft EIS/EIR and identified the Preferred Alternative (PA).