The stretch of California high speed rail currently under construction includes a costly grade separation roughly every one and two thirds miles. The result should be safe and robust, but the expense is evidence of something more than a largely empty continent. And that is in a largely wide open mostly agricultural area of the US.
I assume you're referring to the Caltrain upgrade. It was completely wild to me that a railway line through a major metropolitan area would have level crossings. They're usually a rural thing in other countries.
No, I'm talking about the current round of work in the Central Valley that just started. Currently all the big HSR works are going on there. I can't currently find the report with the oddly high grade separation count and it is possible that my read of that was mistaken, but I am pretty sure that if you look at the recent documents they just moved on from CP1 and started on either CP2 or CP4 in the south end of the Central Valley and it includes a very large number of grade separations. That report was posted somewhere on either https://hsr.ca.gov/ or https://www.buildhsr.com a month or two ago.
Fortunately these Central Valley grade separations are merely expensive while the CalTrain corridor work on the peninsula is experiencing explosive growth of costs from the the complexity of grade separations because of the very tricky maze of rights of way especially in and around Redwood City: https://caltrain-hsr.blogspot.com/2021/05/the-exploding-cost...
