No, there was no safety switch. You can operate the top when driving down the road!!!!! I'd seen a buddy of mine do it in his 67 2+2, and I've done it in my 70 2+2.
FWIW...I remember that a '53 Eldorado has two switches.....one on the left lower part of the dash.....
... and the other one just beside the left rear electric window switch.....(no ''top'' switch on the right side)
... so you're standing outside the car operating and manipulating the top ....