It's a SoCal thing -- LA, the OC, San Diego, etc.. "The 101" is just "101" in the SF Bay Area. I don't know the demarcation line. If I had to draw a line, I would guess a line between the Bakersfield and the SLO might be about right. People talk about "the Grapevine", which is the steep grade on I-5 dropping down into Grapevine CA. But I've never heard anyone say "the Tehachapi".

Although I wonder about south Asians in SoCal. There's a tendency in the S. Asian variant of the English language to drop articles. "I drove car on the 101 to store."
- mark 10-02-2009 5:26 pm