Road

The Pavement Profile Scanner collects high-resolution transverse and longitudinal profile scans. The information below describes a range of potential applications for these high-resolution scans.

Transverse Profile

Transverse profile indices convey the condition of a road at a specific station and the road characteristics that can be measured from a transverse profile increase with the number of points in the profile. Road conditions, such as the bump in between dual tire ruts or the width of a PCC fault, manifest themselves on the scale of 1" and smaller. These conditions, which require a high-resolution profile, are detectable down to 1/4" with the PPS.

Rutting
Several transverse profile classifications exist for analyzing rutting, a condition which affects aging AC roads to varying degrees. Each index indicates a different feature of the transverse profile, and many correspond to road wear and decay. A goal of continuous research in this area has been to correlate these indicators to maintenance and replacement schedules. For example, Superpave relies on mapping lab-measurable characteristics, like binder viscosity and aggregate distribution, to rutting performance in the field. The following list describes several well-supported rutting indices:

• 3.2 m & 1.8 m Bars - Determines vertical distance from average peak height to rut depth
• Cut & Fill area - Estimates the amount of material displaced by the ruts
• Radius of Curvature - Indicates the least flat portion of the transverse profile (lowest radius of curvature)

Intersections usually exhibit advanced states of rutting compared to other sections of roadway. This is due to the viscous behavior of AC under time-constant loading (e.g. vehicles stopped).

Faulting
Construction workers create faults in PCC roads to combat frost heaving and accommodate material expansion. As the roads age, these faults may widen and become increasingly discontinuous, interupting the comfort and safety of travelers. The detection of fault sizes and locations requires a high profile resolution.

Crossfall
Precipitation can gather in severe ruts on well-crowned roads. This water imposes a risk to travelers, and allows water to seep into the roadbed, rather than flowing off. Certain inertial systems continuously report the 3-axis orientation of a vehicle as it drives with great accuracy (<10 arcseconds @ 200 Hz after post-processing). When incorporated with a detailed transverse profile, the crossfall of a road can be calculated.

Another use for crossfall arises in the area of driver comfort. Most roads have constant-radius turns, and an inward crossfall on turns is a common road feature. With a given speed limit and turning radius, there is a crossfall slope at which the driver doesn't have to turn the wheel to round the curve. It is useful to know how close an in-service road is to this comfortable condition.

Shoulder Drop-Off
Transverse profiles collected with the Pavement Profile Scanner provide data suitable for assessment of the condition of the edge-of-pavement (EOP) or shoulder. See our test case for further information.

Longitudinal Profile

Accurate profile data in the direction of travel enables engineers to apply models that simulate the behavior of vehicles while driving on the road. The performance of a vehicle starts with what happens under its tires while driving, and therefore the wheel-path profile becomes the most relevant information when simulating vehicle behavior. The PPS offers a highly accurate and meaningful longitudinal profile.

IRI
Indicators like International Ride Index and Ride Number (IRI and RN) attempt to quantify the ride quality of roads. The fundamental principle of any ride index lies in correlating the results with actual driver experience. These indicators should reflect how a driver feels while driving. Bumpy roads yield a high IRI, while smooth roads yield a low IRI. Reliability of data can be confirmed using multiple passes over the same stretch of road. The PPS includes the collection of longitudinal profile data using rod and level in order to confirm the reliability of high-speed data collection devices.