41 Ford truck door locks

Ive been wondering what the reason behind Ford putting a door lock on the passenger side only on 40,41 trucks? Other years also? Is there some sort of door lock on the drivers side?
At first i thought someone replaced one door on my truck accounting for one lock. But searching photos of other trucks same vintage i see its quite common.
Any info on this would be appreciated!
Thanks

 

Curb side, safe side. It used to say that on Telephone trucks.

And Ford saved the money on that lock and passed the savings on the the buyer.

I used to drive a 47 with one lock, too.

 

If I remember correctly, pulling back on the drivers inside handle locked the door.

 

Putting the outside door lock ONLY on the passenger side was true of Ford cars and trucks from 1926-1941. Cars starting in 42 had outside locks on both sides. Trcuks on passenger side only until 1948.

In the early world of parallel parking it was advised to slide across and get out on the passenger or curbside to avoid accidents with oncoming traffic.
Model As had an inside slide lock on the door for the driver's side.
Later Fords you just pulled or pushed the handle the opposite of opening to lock the door from the inside.

 

All prewar cars and trucks had a tumbler in only the curbside door. I've noticed in a lot of movies that people often got in on that side and slid across.

Chevy's had push buttons by the late 30's, Ford clung to the handle lock.