>nor did supervisors apparently take much note of the fact that crews had stopped calling signals, which should have been easy enough to find out if anyone had been listening to radio transmissions.

And just how, pray tell, would calling the singals on the radio have prevented these accidents? How did the system work before radios came into widepread use (mid to late 1970s), when the railroads were far, far busier (and had nearly twice as many signals per mile)?

The only value that calling the signals over the radio would have in the Chatsworth wreck would be to lay to rest definitively the issue of whether or not Sanchez [though he] saw a green signal leaving the station. Given the poor optics of the color light signals compared to the searchlight type and the inability of the signal departments to aim them correctly, when the sun is at just the right angle, it's all to easy to "see" the wrong indication. It happens quite frequently. In mishaps like this, the issue is what the engineer perceived, because the engineer acts on this information. 99.99% of the time, perception and reality are one and the same.