From your link:

-The train surveys 4,800 miles of track every two weeks.

-The train covers 115,000 miles in a year.

It does not cover the entire system every two weeks.

EDIT: Wikipedia suggests a little over 10,000 miles of track in the UK, so it might be going over it all once a month though I suspect that heavily used high speed lines are covered more frequently than less used lines (which are more comparable to Caltrain).

There are multiple inspection trains, not all of them need to be high speed. The well known "flying banana" is used to cover high speed lines, but for lines with lower top speeds there's also a fleet of loco hauled measurement and inspection trains that cover low speed and branch lines.

This article says the other trains cover routes monthly.

https://rail-record.co.uk/guide-to-network-rail-test-trains/

That's a decent article thanks for posting.

Considering the other problems Caltrian has to deal with not spending much time checking rail straightness above and beyond what's required for the trains to operate seems like a very reasonable allocation of resources.

I think the french do a better job though, the TGV is way smoother than Virgin Trains despite travelling at about twice the average speed. You could do a hand drawn sketch on a TGV, you can't do this on a UK train.

I think this is due to the track being much curvier. Virgin’s trains have to tilt so they can run fast on standard lines. Dedicated high speed lines are built much straighter.

As someone who got stuck in between towns for about an hour while the conductor blamed passengers for the problem – UK rail is mediocre, to put it mildly. The engineer was a bit more constructive and spent his time on the phone with Hitachi. The London Underground is about the only exception here.

Meanwhile tilting trains are designed to tilt so that they can run at faster speeds. They can be designed to ride just fine (e.g. Shinkansen, Amtrak's Acela Express, some of RENFE's AVE lines, etc).

Moving to California gave me a new appreciation for UK rail.

Most of California's rail is low speed and diesel powered. There's almost certainly a higher density of rail service in England, but electrified and/or high speed rail is fairly rare. The infrastructure was so poor around the reign of Thatcher that a lot of the notorious British innovation went into high speed service on low quality tracks.

It's all quite unfortunate as the Brits really had a chance to build out an amazing system (something California hasn't really had the interest in doing). The Underground is pretty great, DLR is at least as dirty and disgusting as BART, and the regional stuff… they don't call it Worst Western Railway for nothing. Electrification is coming at a snail's pace both to California and the UK.

Well Caltrain doesn't have the wrong kind of snow to contend with.

Edit: In case the snow reference went over anyone's head: https://en.wikipedia.org/wiki/The_wrong_type_of_snow