And bear in mind that the Tejon tunnel gets cheaper if the train gets slower. The HSRA assumed the train would cross the mountains at 3-digit speeds. A train going that fast needs a gentler grade, which means longer tunnels. Also (which I didn't know, but which makes sense when you think about it) the faster the train, the larger the diameter of the tunnel needs to be, thus more expensive to dig. Slow the train down, using the time you saved not zigzagging back and forth, and the whole process gets cheaper and more feasible.