By: Tom Tietz and Charles Stuart
In 1947, when Interstate 10 (I-10) was built as a four-lane highway from Ontario to San Bernardino, Calif., it passed through a landscape of ranches, orchards, and open fields fringed with trees. Originally this section of roadway was assigned as U.S. 70-99, and in 1957 it was reassigned to become part of I-10, which stretches from Santa Monica, Calif. to Jacksonville, Fla.
Traces of the historic Rte. 66, or “America’s Main Street,” can still be found running parallel to the I-10 freeway. Today I-10 passes through the familiar urban landscape of homes, business parks and industrial warehouses.
Looking back, it is clear today that California Department of Transportation (Caltrans) highway engineers, working under the provisions of the post-WWII Federal Aid Project, made some outstanding decisions when they designed this concrete pavement back in 1945.
Perhaps the most remarkable feature of this 70-year-old highway is the pavement—an 8-in.-thick section of concrete making up the top layer of the roadway including tie bar reinforcement, an innovative practice at that time.
Much of this original concrete pavement is still in use today and has survived an incredible beating from the unrelenting forces of traffic and time. By today’s Caltrans design standards, to handle the current traffic loads, this pavement should be 50-75% thicker with more reinforcement, dowels and tie bars.
Commenting on the longevity of this section of I-10, Caltrans Director Malcolm Dougherty said, “This is an excellent illustration of the long-lasting benefits of investing in transportation infrastructure, and a strong indication that the work we are doing now to ensure a resilient and sustainable system will serve California’s people and prosperity for generations to come.”
The I-10 corridor now connects Los Angeles, San Bernardino, Palm Springs and the nation, carrying increasing numbers of passenger vehicles, buses and heavy freight trucks. As one of California’s busiest freight freeways, I-10 has stood up well to 24/7 usage with current average daily traffic of 280,000 vehicles, compared to 90,000 vehicles in 1993—an increase of 300% in just over 24 years. Driving along the I-10 freeway today it is hard to imagine how any roadway survives the traffic loads of 100 million vehicles per year with only minor maintenance, but it has endured without significant restoration or upheaval to traffic flow.
Until recently, most concrete pavements were designed for a 20-year life span, and on that basis, the I-10 pavement has lasted about 50 years beyond its design life, an outstanding accomplishment in terms of sustainability, economic benefit and social value.
In 1967, some 20 years after the initial construction, in an effort to reduce congestion and increase mobility, the highway was widened to eight lanes on the section from Vineyard Avenue in Ontario to just east of Valley Boulevard. The new lanes were constructed with concrete pavement on cement treated base. At the same time, the original 1947 concrete pavement was improved using an innovative diamond-grinding process to provide a smoother ride and longer life.
When the first engineers set out to design rigorous specifications for the San Bernardino State Highway (I-10) contract in April of 1945, sustainability was not part of everyday vocabulary. Even so, the highway has proven itself sustainable in every sense. For 70 years it has stood up to the rigors of increasing traffic volume and bigger, heavier truckloads. Indeed, the original engineers and road builders delivered a road that would serve the area for many years without major repairs. Ultimately, the long-lived I-10 freeway has played a beneficial role in establishing California as the world’s eighth largest economy in the United States.
