I-238

About I-238

Interstate 238 is a short connector in the East Bay of the San Francisco Bay Area in California, running between Interstate 880 in San Leandro and Interstate 580 near Castro Valley, a distance of about two miles. It is famous as an anomaly in the Interstate numbering system because it has no matching two-digit parent route. Under the normal convention a three-digit number prefixes a single digit to its parent, but there is no Interstate 38, so the number does not fit the standard pattern.

The number arose because California requested it to match the existing state highway code numbering, since the route had carried the State Route 238 designation, and because the available three-digit combinations based on Interstate 80, the main two-digit route in the area, were already in use in the state. The result is the only signed Interstate whose number has no corresponding two-digit parent.

The route serves as a connector between Interstate 880 and Interstate 580 and is used along with Interstate 880 as an alternate truck route in the East Bay, since trucks are restricted on part of Interstate 580.

State-by-state mileage

State	Miles
California	2.2
Total	2.2

History

The roadway was first built as a freeway in the 1950s and carried a state route designation. In 1983 the segment between Interstate 580 and Interstate 880 received Interstate funding for upgrades and was redesignated Interstate 238, preserving the existing 238 number from the state highway code rather than assigning a conventional auxiliary number.

Major cities and places

Did you know

• It is the only Interstate with no matching two-digit parent, since there is no Interstate 38.
• The number was kept to match the California state highway code.
• It connects Interstate 880 with Interstate 580 in the East Bay.
• It serves as part of an alternate truck route in the area.