In a message dated 6/27/03 9:25:16 PM Eastern Daylight Time, imperial67@xxxxxxxxxxxxx writes:
The only safety benefit I can imagine from the 1968 setup would be that having the inner lamp not used by the brake and turn signals, a non-flashing turn signal would be slightly more obvious at night (because you could see that part of the lamp is brighter).
Honestly, I think they just did it to save a few cents, or chances are some people might have complained that the giant brake lamps of the '67 were too bright to cars following at night. One things for sure, the 67 certainly compensated for the tiny brake lamps of the '64-66!
I can't attest to the reason, but starting in '68 none of the American vehicles had more than two bulbs per side that functioned as turn signal/brake lights. I do not believe that it could have been a money saving thing as Imperials required a new wiring harness to change to the different bulbs. It seems to me that any savings on bulb cost would havebeen insignificant relative to the change of wiring harness cost.