Foothill Expressway was originally a train line. If you know where the old Fry's Electronics was in Palo Alto, the line branched off from the main Southern Pacific line near there, went by the loading docks behind the buildings where Fry's was - it was a major cannery at the time - went through what is now Bol Park, and turned onto Foothill where the VA hospital is now.
Foothill makes a bend to the right at Homestead, but the train line continued straight through at that point, going through what is now the Trader Joe's parking lot. If you notice a diagonal NW-SE path through the parking lot that continues onto Homestead Ct and Peninsular Ave, that was the railroad alignment.
Highway 280 wasn't there at the time, of course, so the line continued straight through to the still-existing Union Pacific line that serves the Kaiser Permanente quarry, and then down to the line that parallels Winchester Blvd in Campbell. This right-of-way currently has three tracks on it: northbound and southbound light rail lines, and the Union Pacific line.
I used to live in an apartment that overlooked this railway, and it was great fun to hear and see the Union Pacific freight train that comes through twice a week. Just like at Fry's, you can see several of the loading docks in the buildings in downtown Campbell.
On the east side of that line, there was a branch that went south to serve the New Almaden mines. If you ever wondered where Camden Ave in San Jose got its name, it wasn't from the city in New Jersey. This line was called the Campbell-Almaden line, so CAMpbell-almaDEN is where the street name came from.
If you drive Camden Ave from Campbell, you may notice an oddly gentle right turn at the junction with Hillsdale Ave. This turn was gentle for the trains. Farther south, Camden takes a slight right at Clovis, just before Blossom Hill, and there is a powerline right of way that continues in a straight line where the railroad was. The tracks then crossed Guadalupe Creek and followed what is now Redmond Avenue, then turned south toward New Almaden.
Back to Palo Alto, if you know of Hawthorne Avenue, three blocks northwest of University, that was a train line too! Lytton and Emerson were streets at the time, but Hawthorne was a spur line that served the Catholic University in Menlo Park (now St. Patrick's Seminary). It branched off the main Southern Pacific line by the water tower, followed Hawthorne and then made a bend to the left onto what is now Middlefield, then a gentle right into the University. It split into two tracks on each side of the main building.
If you are interested in this stuff, I highly recommend the USGS topographic maps. They have the complete historical maps all online!
https://ngmdb.usgs.gov/topoview/
For example, here is the 1899 Palo Alto topo where you can see that Hawthorne train line:
https://ngmdb.usgs.gov/ht-bin/tv_browse.pl?id=8db99b827f55d7...