here you go...lots of videos https://www.youtube.com/results?search_query=diy+handicap+ramps there were lots of videos for the dog ramps but these might work better
My dog has liver cancer and it's hard for her to climb steps. I USED A OLD WOODEND LADDER I found at the Good Will....I attached a piece of wood that was large enough to cover the ladder, glue it down and nailed it. Than I had small piece of strip wood attached them to the wood the illusion of stairs so the dog will walk the ramp. Now lay plank on the stairs. My dog uses it everyday. Hope it helps
Thanks. The ladder was a good idea but not nearly long enough for my project. What did you use for feet?
Outdoor plywood over the top. Paint it w/ out door paint. Screw it down.
you never tell us how high the transition is how many feet/high up is the top why does it need to be 16ft long? making the ramp in 2 8ft sections so the grade is not so long--example https://www.youtube.com/watch?v=Mwm26bcM5uo-- https://www.youtube.com/watch?v=A7PQE2Qtspk ; 4x4'S cut into the lengths make perfect legs/posts with lrg bolts/metal brackets to secure to upper ramp https://www.youtube.com/watch?v=QyIJZPPAkl0 not sure you need to "miter" anything just straight cuts at an angle with any saw( even hand saw) if thats all you have will work fine ; you could use pallets with plywood on top ; here are lots of ideas videos https://www.youtube.com/results?search_query=handicap+ramp+construction+details ;the cat litter probably hurt the dogs feet or add Beads of silicone on the boards in long rows/strips every couple inches diagonally this gives them traction and allows water snow melt to run off easily better buy the large construction tubes and good caulking gun it'll be cheaper