I've just photo-enlarged "Tangent running cost on grades",one of 4-tables of Fig.4-3,Pg.115,HIGHWAY ENGINEERING,by Clarkson H.Oglesby & R.Gary Hicks,4th-Edition,1982,JOHN WILEY & SONS,INC.,N.Y..
It's too small to work with in the book,but preceding the table is a comment on page 114 under 'COSTS RELATED TO GRADES'.
They mention that on downgrades flatter than 2%,the energy demand lowers and costs decrease roughly the same amount as the increase on upgrades.
Then,'There is,however,little if any further cost decrease on downgrades steeper than 2%,since braking is required.'
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In the context of today's hybrid vehicles I think we'd have to rewrite this part of the chapter,however with respect to the Viking trailer,this explains why I'm experiencing lower than expected results.
Added weight of the trailer will induce runaway speed if not compensated for with braking which kills otherwise useful kinetic energy.
Without the trailer,the little air drag present is enough to discourage runaway,and I don't lose fuel energy to braking.
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As a 200-pound plug-in hybrid battery range-extender trailer,with 400-pounds of extra Li-on batteries, the trailers inertia and momentum could be 'harvested' with an EV.
Not so as a pull-behind micro-RV caravan.Weight's go to go!
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I'll have a look at the 'new' tables 'n see where that goes.
