**Pavement Smoothness Redirection Efforts**

On July 12, 2001 a pavement smoothness phone conference was held with
various federal, state, academia and industry representatives to gather
information on where everyone is at and to define what work items need
to be accomplished and how to go about doing that. Those in attendance
for the phone conference were John Andrews MD-DOT, Jim Delton AZ-DOT,
Ken Fryer MO-DOT, Ken Fultz TX-DOT, Kent Hansen MD-NAPA, Keith Herbold
FHWA-MRC, Steve Karames MI-UM, Starr Kohn MI-SMI, Dave Law FHWA-SC,
Laurin Lineman FHWA-EFL, Byron Lord FHWA-HIPT, Kevin McGhee VA-DOT, John
Perry FHWA-HIAM, Jim Sorenson FHWA-HIAM, Mark Swanlund FHWA-HIPT, and
Bruce Wasill FHWA-WFL.

# Background: A few years ago mechanical type profile users began to move away from using those type machines to measure pavement profiles towards the next generation non-contact inertial profile devices. These devices could be used for both construction quality control and if desired also for acceptance testing. This allows one piece of equipment to more efficiently collect data for both construction quality control and network management. To showcase the inertial profilographs six to eight equipment demonstrations were held so that contractors and state highway agencies would become more familiar with what was available in the lightweight area.

# The Four Milestones of Pavement Smoothness: Four basic things need to be developed such as, equipment specifications, a draft guide specification for construction quality control, a calibration procedure and to get better training and understanding on what profiling is all about. Equipment and draft guide specifications for construction quality control are needed so that there is uniformity in the type of equipment being used to measure pavement smoothness. A calibration procedure for inertial profilers is also needed to be able to use the lightweight profilers on a routine basis and to encourage most contractors to purchase and use one. The fourth milestone is to provide better training and understanding for both engineers and technicians on what profiling is all about, its strengths and weaknesses, how to use the tools from both the owner agency and the contractor standpoint and how to use the inertial profilers to get some level of confidence in the data being collected. None of the four milestones have been completed to date. However, the AASHTO Subcommittees on Construction and Materials and the Joint Taskforce on Pavements have all been working on various activities.

# Short Term Calibration; Test Sections, Time and Temperature Constraints

Larry Schoefield has done quite a bit of work on PCCP with the
mechanical style California type profilographs. His studies have shown
significant differences in profile results due to temperature and time
of day variances and its effect on the curling and warping of the
concrete slabs. One concern with test sections is that they need to be
relatively stable and never change during the duration of the project.
Keeping a test track is potentially seen as being a maintenance issue as
well. However, test tracks will probably still be needed in the short
term as long term calibration procedures for inertial profilers such as
DMI , Bounce Tests and Four Post Shaker Tables as well as others
currently are under development.

# Long Term Calibration; DMI, Bounce Test & Four Post Shaker Tables

Long term calibration equipment may include the DMI check which makes
sure that all of the inertial profiler sensors are working properly or
the Bounce Test makes sure that the accelerometer is blanking out the
height signal and that everything is working properly. It may also be
possible to move from a certification test track to a four post shaker
table where you could go in and put a known value to see if the
equipment can measure it. Contractors may buy this device, follow the
calibration procedures and use it but may also be resistant to moving
their inertial profilers all around to the one or two shaker tables that
may be available to calibrate the profilers in the field. Vendors and
manufactures at the recent ASTM meetings in Norfolk, Virginia shared
their thoughts and feel that the real issue is that of a true reference
device, one that can provide a true profile. The shaker table idea was
discussed and a lot of the vendors and manufactures asked if as such,
are we really operating like we would operate in the field for sitting
semi stationary on a shaker table? Maryland is currently working on a
stationary vibration test (ie shaker table) across the entire frequency
band and this may be as close as they can economically get to a portion
of the validation and or calibration process.

# True Reference Device: A true reference device should be highly portable, accurately measure smoothness, can be operated by a contractor for construction quality control and has a direct correlation to the high speed devices currently being utilized.

# Industry Perspective

It appears that industry is in a wait and see mode to see whether we are
willing to move forward with pavement smoothness initiatives. We need to
specify exactly what we want so that industry will be able to develop
equipment that can be competitively bid. However, this may have already
initially been provided by the existing draft specifications for
inertial profilers and a set of procedures for calibrating that
equipment such as those developed by ASTM. One concern that we share on
an industry wide basis is that there is currently no uniform set of full
size or lightweight inertial profiler specifications that all vendors
develop and calibrate their equipment by. State Highway Agencies and
contractors need to know what they are buying. The specifications should
address having the vendors utilize uniform filtering and analytical
processes so that they are measuring the end product to the same level
of accuracy and also adhere to the same level of statistical validation.
There is nothing wrong in using some type of mechanically based
calibration procedure for the manufactures to certify the equipment they
build. However, it may be difficult for a contractor to understand their
need to have one and especially to get it calibrated at a regional
center once a year.

# What We Are Looking For

We are looking for a machine that is accurate enough that it can be used
as a cradle to grave piece of equipment. When a construction project is
built this machine can be utilized to get initial numbers on how smooth
the pavement is. Years later when the machine is run over that same
section of pavement it should measure the same kind of data to assist in
determining how long the pavement retained its smoothness index. This
same machine should also be precise enough so that the construction
industry feels comfortable paying bonuses and penalties during the
construction process and allowing the owner agencies to transfer the
risk and reward along to the contractor for doing a better job. It
should also be able to let the engineer know how far off from a true
reference device this machine really is. Finally this machine should be
capable of providing quality control information to the contractor and
assist them in understanding what they are and are not do in order to
get the product to what it's supposed to be.

As such we need to come up with a national specification that supports
both the equipment and construction sides. Validation and or calibration
of the equipment an agency or contractor receives and whether it meets
the specifications also need to be addressed. The ultimate goal is to be
leaders and provide this information for everyone so that everyone is
doing the same thing.

# Where Do We Go From Here

Two meetings will be scheduled back to back, one so that we can go away
and finish up and the other so that we can come back and produce the
final products. The dates for the two meetings will be September 4 -- 7
in Ann Arbor, Michigan and October 18 - 21 in California prior to the
RPUG meeting. Everyone has agreed to assemble what has been worked on to
date and to share that with everyone. Those who are still working on
their piece of the puzzle can continue and get it polished up prior to
sharing it with everyone. Guide specifications, protocols and test
procedures should be electronically shared with the rest of the task
force prior to August 1, 2001. This will give ample opportunity for
review prior to the September meeting in Michigan. Funding to get a few
of the taskforce members together to finish developing these initiatives
will be provided through FHWA invitational travel.

The four basic things the task force will work on to various degrees is
to develop a lightweight inertial profilometer equipment end product
accuracy type specification (Star Kohn and Others); an AASHTO general
type guide specification for states to consider as a basis for
implementing lightweight profiling for construction quality control (Ken
Fryer and Others); a calibration procedure for the lasers and
accelerometers which meshes with the equipment and guide specification;
a separate validation procedure to assist in producing a reasonable
profile; where to look for must grinds; and finally as part of educating
the contractor and state communities the second training course should
come out of the four milestones being put together. The outline,
objectives and instruction for the first NHI training course #131065,
"Pavement Smoothness Factors Effecting Inertial Profiler Measurements
Used for Construction Quality Control" was reviewed in mid July and is
moving forward with development of the course. The two major emphasis
areas for this course is to let everyone know why they are doing it and
to make sure they have the information they need to move forward.

**Contacts:**

Mark Swanlund, Office of Pavement Technology (Co-manager)

David Law, SC Division (Co-manager)

Byron Lord, Office of Pavement Technology