>Please don't tell me that Metro-Link had not included that long-ago established requirement from the get-go. Indeed, in virtually every signal system design, including Metro-Link's, the minimum permissible signal spacing is predicated on that very action!

Fortunately this specification is contained, in so many words, in the CFR regs. Sometimes I think they've lost sight of fundamental signal principles. At Pitt (just west of Dixon on the Cal-P) time out of signals is 7 minutes and track speed is 79 mph. At the I St Bridge (Sacramento), track speed is 20 mph yet time out of signals is still 7 minutes. In the old days, time out of signals at the Bridge would be something like 2-3 minutes (and the track speed was 20 mph). At N Jack London going southbound, you get FY and then Y to proceed into the depot. At Emy, it's FY, Y, FR, then stop at the depot -- the very epitome of consistentency.