The fact that the Tehachapi alignment has remained largely unchanged since 1878 is quite a tribute to the engineering genius of William Hood. Of course topography has played a big part, constraining any alternate approaches. The big flood of 1983 was the death knell for Tunnel 1/2, and then the Caliente double track project substantially altered the rest of the bottom end. And of course the '53 earthquake shook things up a bit (har har,) but otherwise the railroad has remained amazingly intact.