I have about 18 feet of track on an incline of approximately 1 1/2%. If I let a car go on that grade it is going fast enough to knock the coupler off for sure and maybe do even more damage. Of course, having the track end at a solid wall may contribute to the damage.
My point really is that a 1 1/2% grade is way too steep for any meanful test unless there was a really long - 100 feet? - level track for the car to coast to a stop.
Another party to this discussion made the point that testing the truck alone and testing trucks with a car might yield different results.
