Copy and paste:
Wagner Electric invented a dual-cylinder brake system in 1960. This system had a dual master cylinder separating front and rear hydraulic lines. In other words, if one line developed a leak, the other line could still work, and your brakes wouldn’t completely die. This safety measure was mandated by the federal government in 1967.
I have my own opinions on why the USDOT ruled a dual reservoir was needed.
*) There was no national speed limit until 1965 when the speed limit was set to 70 mph. Speeds were increasing.
*) Sometimes a lack of manufacturer's required periodic braking system maintenance (originates with DOT3 (hydroscopic fluid), moisture, rust and leaking seals).
*) More panic braking (braking system stress).
*) Vehicle speeds were too fast for our brains to react and downshift and/or use parking/emergency brake (instinctive reaction).
It makes no sense to pick out just one classic/antique part and worry about it's effectiveness (safety wise) and overlook the plethora of other parts. If you really want to get serious about it, our old trucks need modern brakes, a modern suspension, modern steering, crumple zones, driving assistance tech, video cams and airbags just to be safe in modern world of driving.
When I'm in my 55, I like to pick roads less traveled and slow down.
