Face Dipstick 2200 Series, Operator'S Manual

Page: 48 / 107

C
HAPTER
5 PROCESS
5-6
Half-Car IRI
If you select two Runs and use REPORT/IRI, you will get a graph which displays the cumulative
value of the "Half-Car IRI" at each point on the profile, as well as the 50-ft running Half-Car IRI.
The half-Car IRI is based on the motion of the center of a transverse axle, at a point halfway
between the left and right wheelpaths. It is almost always lower than the quarter-car IRI because
the surface irregularities under the left and right wheels tend to be at least slightly out of phase.
Because it emulates the motion of the front "half" of the car, it is called "Half-Car IRI".
Notes
If you select a Run and use REPORT/NOTES, you may read any N otes that you collected during
the Run. If you have pressed the “S” or “C” or “T” keys while you collected data, these will
generally be in the form
Note Step 27 : or
Corner Step 113 or
Turnaround Step 50
These "Notes" can serve to remind you of
particular features that you want to
remember about the pavement surface -
such as the locations of cracks or other
features, or the locations of the "corners"
of the boxes where you collected the data,
or where you turned around in an "out-and
back" Run. If you have marked them, the
"Corner" Notes will be used automatically
when you "Unbox" a Run, and the
"Turnaround" points will be automatically used for any "Test Track" Runs you have collected.
The Running IRI is based only on the last 50 steps
So it is more sensitive to individual flaws
The Cumulative Half-Car IRI is based on all data
So it tends to smooth out after many steps.
It represents the “overall roughness” of the profile
and is much less sensitive to a single flaw