If they used a dynamometer there are a few more potiential differences. One big one is that the rolling resistance on a Dyno is different because of the "double deformation" introduced by the rollers vs the single deformity for each wheel that occurs on pavement. Also, dyno testing usually only invoves two wheels. The double deformation has the effect of offseting some part of the unaccounted for rolling resistance of the non-driven wheels, but the difference is significant enough to be a factor.
They used a four-wheel, dynamometer. If you'll click on the page number links in my original posting, you'll see the specific pages my post references. Sad to say but at $15/copy, it is a little pricey unless you have an interest in the subject.
I would feel much better about this paper if they had gotten 'track time' and replicated the results 'in real life.' I know it is expensive but so too is normal dynamometer time.
One area that I would like to see is a Monte Carlo simulation of "n" vehicles with different characteristics practicing pulse and glide on a circular track. Ideally this would allow a mix of vehicles and perhaps address questions of:
- traffic density versus Pulse and Glide or steady state - is the transition smooth or are there non-linear effects that defeat pulse and glide above some given threshold?
- what happens when hetrogeneous vehicles attempt pulse and glide as the traffic density increases - is this a case where the least optimized, 'pulse and glide' drives everyone else to adopt their style?
- can we characterize the driver workload as a function of different "pulse and glide" regimens versus steady speed?
These are questions that address 'the commons', the roads we share with other drivers.
Bob Wilson