[relee]

... Just doing a rough estimate, but if they fell 85 feet and traveled 200 feet laterally then they left the embankment about 59 mph and hit the tree at about 77 mph....

So, was the tree going 18 MPH or did gravity increase the car's speed?

[burzum]

So, was the tree going 18 MPH or did gravity increase the car's speed?

The vertical component of their speed would have been about 50 mph.

Actually CNN noted that they hit the tree 15 ft above the ground changing these numbers to about 65 mph when they left the embankment, and about 80 mph on impact (45 mph vertical component). Either way they left the embankment at a very high speed which probably indicates they underestimated the braking distance required.