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Interstate 6 has never existed.

I-106 is an early California proposed number inconsistent with the interstate highway numbering convention.

I-106 (preliminary numbering)  California (link)

On April 1, 1958, California submitted to AASHO a numbering plan for its proposed interstates, including 3-digit spurs numbered in the low 100s and not associated with their parent interstates. Interstate 106 was the proposed number for what became the old I-105 and I-110, where the Santa Ana and San Bernardino freeways meet. [1note]

This number was not compliant with AASHO's numbering convention and was rejected.

On August 7, 1958, California had bought in to the system and submitted I-105 and I-110. AASHO wanted to combine them into a continuous I-110, but the state replied that ramp configurations made it impossible for motorists to follow the entire route. Hence the two spur designations. [1note]

These numbers were approved, along with the rest of California's original interstate highway system, on Nov. 10, 1958. [2note]

See also:


  1. Summers, Stephen. "Interstate system route numbering." http://www.nwindianahwys.homestead.com/INTER_MAIN.HTML. (29 May 2003)
  2. Faigin, Daniel. "California Highways (www.cahighways.org): Interstate Highway Types and Interstate History." http://www.cahighways.org/itypes.html (29 May 2003)