If we do a some simple math, a 12x16 platform is 192sf. If you put two 1500lb cars on it, that is 3000lbs. 3000lbs/192sf = 15.6psf.
If we google floor joist load tables, a 2x8 on 16 inch centers can span 12ft, floor live loads are 30-40psf.
Cars don't care about floors being flat like people do. The platform is made from 2x8 on 12 inch centers.
There is a 2x6 that doubles the front 2x8, which threw some people off. The ramps are 2x6 with blocking and 2x4 reinforcements.
The platform is not an issue. Getting a car up there is where trouble lies. If you had a forklift it could just be set down on it.
But I am using ramps, which puts a horizontal load on the platform, which it is not "spec'd" for.
The pic of the 4500lb Explorer trying to drive up 45-degree ramps is total Troll material. That would be disaster!
I use a winch to PULL the car up the ramp, so instead of pushing on one side, the loads are like squeezing the platform.
Once the front wheels are on the platform, then I raise the rear of the ramps so the angle is not extreme.
The ramps rest on a 1.5inch tube so they can rotate.
And notice I use a wireless remote on the winch so I am not in danger of impending collapse..
The danger is the winch mount gives way and goes flying towards the car and then the car rolls back off the ramp,
but once the front wheels are on the platform less danger, but still dangerous.