Damion Orsi, P.Eng., PMPProduct ManagerFugro

ERPUG - September 12, 2013

Different Methods of Collecting Transverse Profiles and Calculating Rut Values

Fugro (Roadware)

History• 1969: Company created to carry out pavement data collection surveys • 1977: Development of Automated Road ANalyzer (ARAN) • 1984: First ARAN sale - Italy - still in service• 1995: Development of Automated Detection software (Wx) • 2003: Integration and Development of Laser XVP Transverse

subsystem (LRMS)• 2009: Integration and Development of GPR • 2010: ARAN 9000 Release• 2011: Vision software and iVision Web Application Release & 3D

LCMS Integration• 2013: Relaunch of ARAN 7000 (Portable Profiling System)

Fugro Roadware Business Lines

ARAN Products • More than 100 successful deliveries in

20 countries and across 6 continents

Services• 400,000 km of data collected annually• Over 2 million assets delivered• Fleet of 22 ARAN vehicles• More than 100 Data Analyst staff

3D Road GeometrySkid / Friction Testing

Structural Assessment

Asset InventoryPavement Condition

Range of Products & Services

What is a Rut?

• Surface depression in the wheelpath• Rutting appears as long smooth grooves in each

wheelpath

Source: Pavement Interactive

What Causes the Rut?

• There are 2 causes of rutting; – Instability Rutting – Consolidation Rutting

• Can’t tell what the cause is from the surface

Why Measure Rutting?

• Safety– Hydroplaning– Ice (Freezing of Ponded Water)– Loss of Vehicle Control

• Liability

Methods

• Ultrasonic Sensors (since 1980’s)• Multi Single-Point Laser Systems (5,19,N-points)• Scanning Laser (LRMS)

– 1,280 points across travel lane• 3D Scanning Laser:

– 4,000 points across travel lane• Different Algorithms provide different answers

Collecting High Speed Transverse Profiles

Multi Single-Point Sensor Systems

Note – 5 sensor system has missed the peak and valley

LCMS – 3D (4,000 Transverse Points)

High Speed Transverse Profiles

• Systems can collect up to 4,000 points across at intervals as small as 5 mm

• Typically results are smoothed and reduced to approximately 200 points

• Lots of researchwith comparisonsto field measurements

How often should we measure rutting?

• Most clients and agencies specify a reporting interval

• Very few specify a collection interval– Providing mean rutting value of many profiles – More profiles are likely to increase the

number of invalid profiles

How to measure manually?

• Wire vs. Straight Edge?• Length of straight edge?• How wide is your ruler or

wedge?

Many More Assumptions!

• Do you measure the rut vertically or perpendicular to the wire / straight edge?

• Are you biased to looking for ruts in the wheelpaths?

• What are the rules about where the straight edge or wire can be placed?– Can it rest on the shoulder or other lane?– Can it cross the middle of the lane?

Problems with Transverse Profiles

• Many problems are more difficult to avoid during high speed testing

• Not always as obvious how to deal with:– Edge drop off– Curbs– Street hardware– Potholes– Distress– Debris

Optimize Rutting in the Wheelpaths

• AASHTO R 48 defines rutting as:A longitudinal depression in a wheelpathconsisting of consecutive rut depth determinations that measure a depression and extend for more than 50m

• So why do we only look at one transverse profile at a time?

Source: FHWA

Rutting ComparisonStraight Edge vs. Wire

Why don’t we use multiple profiles for more than just an average?

• We started to look at the profiles to look at where the deepest points occurred…

What if we use multiple profiles?

• Built an algorithm to track and optimize the location of the rut– Cap the maximum distance it can move

horizontally– Optimize the sections to determine the

maximum rut over the entire length

Single Profile Rut Depth

Multiple Profile Rut Depth

Single Profile Rut Depth

Multiple Profile Rut Depth

So how does this change the result?

• In our trials, 75% of the rut depth changed by less than 0.5 mm

• The rutting was always a little bit lower if the optimal path was used.

Where do you measure cross-slope?

• Cross-slope is measured for safety:– Drainage of water– Banked turns to reduce horizontal forces on

vehicles• Where would you

measure?– Average slope– Slope between

wheelpaths

Conclusions

• Both point laser and scanning laser systems are capable of measuring rutting

• Slight differences in the equipment mean minor variations in the results

• The more points you use the better to find road artefacts and lane edges

• Difference in the analysis techniques have as much effect on results as differences in hardware

Thank You

• Acknowledgement – Colleague D.J. Swan, P.Eng.• Damion Orsi, P.Eng., PMP - dorsi@fugro.com