Hi. This trophy is pretty easy, as it requires the player to drive any Ford with a cumulative total of 50 seconds. Just fail certain jumps that will make your car fall into the valley because of insufficient speed. But your car will spawn back at the jump-ramp without any damage so just hold to the accelerate button and fail the jump 12-15 times. BOOM! Trophy won!
I did it in ~2min on the jump near the Riverside Drive with my Shelby GT_500 {Police}. Im also attaching the location of the jump on the map. It's
Jump no. 32. [P.S. This is my first solution on this site, hope this helps!]
https://app.box.com/s/qm8gyccfgy1wtyq4we8vf4j78hg3ibo9