The zone has a variety of industrial and commercial buildings available, ranging in size from 1,000 to over 500,000 square feet. New speculative or built-to-suit construction has increased year-over-year, which results in a newer, more environmentally efficient, industrial inventory. With over $1 billion of infrastructure improvements under construction, the San Bernardino County RMDZ provides a world-class and well-connected network of highway, airport, and rail systems. Major highways traverse the county from Los Angeles and Southern California to Nevada and Arizona, and include I-10, I-15, I-40, I-215, SR-60, and SR-210. Ontario International Airport is the largest commercial and passenger airport in the Inland Empire and is a corporate alternative to LAX. Extensive rail service provided by Union Pacific and BNSF easily connect manufacturers to the Ports of Los Angeles and Long Beach and to markets east of the Rockies.