List of Interstate Highways in California
This is a list of Interstate Highways in the U.S. state of California that have existed since the 1964 renumbering. It includes routes defined by the California State Legislature but never built, as well as routes entirely relinquished to local governments.
Each state highway in California is maintained by the California Department of Transportation and is assigned a Route number in the Streets and Highways Code. Under the code, the state assigns a unique Route X to each highway and does not differentiate between state, US, or Interstate highways.
Overview
- U.S. Routes and state highways that traverse California are also defined in the California Streets and Highways code as state routes. This list does not include these state routes as they are listed separately.
- A few cases exist, such as I-110, where a defined California State Route partially overlaps with a federally defined Interstate Highway, while the remaining portion is signed as a state highway. This table only addresses the portion signed as an Interstate in these cases.
- One Interstate Highway—I-305—is defined only federally; the state calls it part of US 50. It was signed as part of Business Interstate 80, the only state-maintained Interstate business route in California.
- Conversely, a few segments exist that are not part of a federally defined Interstate Highway but are still signed as such by Caltrans. Examples include I-80's westernmost segment between US 101 and the Bay Bridge.
- Lengths for each state route were initially measured as they existed during the 1964 state highway renumbering, and do not necessarily reflect the current mileage.
- The years listed reflect when the route was affected by legislative action, this is not necessarily the same year as the actual construction or signing changes to the route.
- Concurrencies are not explicitly codified in the Streets and Highways Code; such highway segments are listed on only one of the corresponding legislative route numbers. For example, the I-80/I-580 concurrency, known as the Eastshore Freeway, is only listed under Route 80 in the highway code while the definition of Route 580 is broken into non-contiguous segments. When a highway is broken into such segments, the total length recorded by Caltrans only reflects those non-contiguous segments and does not include those overlaps that would be required to make the route continuous. Furthermore, Caltrans may not sign all concurrencies, and instead may only post the highway shields for the route with the contiguous segment in the code.
- Some highways are not contiguous as the state has relinquished control of small sections to local governments. The stated length of the highway may or may not reflect the portions under local control.
Primary Interstates