BRIEFING

August 2001

# ROSAN, A Pavement Roughness Measurement Devise

Federal Lands Highway has obtained three ROad Surface ANalyzers (ROSAN)
units manufactured by Surfan Engineer and Software, Inc. (SES). The
ROSAN is a non-contact, high speed, portable, profile and macro texture
device. ROSAN was originally developed by the Turner Fairbank Highway
Research Center in partnership with SES.

ROSAN is a laser-based profiler using an accelerometer established
inertial reference. This profiler is capable of measuring longitudinal
texture profile as well as longitudinal pavement profile at highway
speeds. The system consists of a laser, optical interface,
accelerometer, pulser, and computer. The ROSAN unit, with the exception
of the computer, fits in one case weighting 94 pounds and is
transportable. ROSAN can be mounted on vehicles having a step bumper and
any vehicle to which mounting brackets can be permanently installed.

The ROSAN system is capable of sample intervals ranging from 0.25mm to
25.0mm and sampling speeds ranging from 15 mph to 65 mph (dependent of
the sampling interval). At a sampling interval of 0.25mm the maximum
sampling speed is 15 mph and at 1.00mm sampling interval the maximum
sampling speed is 60 mph.

ROSAN has the capability to analyze longitudinal traces for texture in
accordance with ASTM E 1845, smoothness simulating the California
profilograph (Profile Ride Index, PRI), and roughness in accordance with
ASTM E 950 & E 1926 (International Roughness Index, IRI). Analysis of
texture can be performed on traces with a sampling interval of 1.0mm or
less. The simulation of the California profilgraph can be performed on
traces with a sampling interval of 10.0mm or less, and roughness
analysis can be performed on traces with a sampling interval of 25.0mm
or less.

Since taking delivery of the ROSAN system in May of 2000, FLH has
evaluated its smoothness and roughness measuring capabilities as well as
recommending and having changes made to the software. In August of 2000,
the three Federal Lands Highway offices met at the MnRoads test facility
where over 216 longitudinal traces were taken to evaluate ROSAN's
variability by; operator, data acquisition speed, and vehicle type.
Results from the evaluation produce an average IRI of 1.726 m/km for all
traces taken with an overall standard deviation of 0.216. Also, in other
testing, the ROSAN California profilograph simulation has been evaluated
against the California profilograph. The testing of the ROSAN simulation
produced an average PRI of 30.39 in/mi and a standard deviation of 3.17
in comparison with the California profilograph which produced an average
PRI of 32.63 and a standard deviation of 0.12

Currently the three Federal Lands Highway offices are collecting
International Roughness Index (IRI) data on projects on both the
original surface before paving and on the final surface. The data will
then be used to write a roughness improvement specification based on
IRI. The roughness improvement specification is planned to model the
recently FLH adopted California Profilograph improvement specification
using a 0.0 inch banking band which bases the contractor target value
for smoothness on the existing roadway condition and how many
opportunities (lifts or type of rehabilitation) the contractor receives
to improve.

NCHRP Report 441, Segregation in Hot-Mix Asphalt Pavements identifies
ROSAN as a technology for use in the identification of aggregate
segregate in hot-mix asphalt pavement. FLH is currently evaluating the
ROSAN texture measurement module to obtain the necessary data to develop
a construction quality control specification for aggregate segregation.

Federal Highway Administration

Laurin Lineman, Division Materials Engineer, EFLHD, Phone: 703-404-6268