Introduction

A pavement profile analysis is essential to optimise the management of pavement maintenance. The GLP is a high-speed 3-Dimensional Pavement Profiling System utilising up to 15 Selcom profile sensors, inertial reference systems and advanced data acquisition. The GLP provides precision profiles and detailed analyses of the pavement surface conditions. The unit has a measuring width of 3.0m and is classified as a Class 1 profilometer in accordance with the World Bank classification. The operating speed range is from 30 to 100 km/hour.

In order to achieve a maximum measuring width of 3.0m, and still be within highway operating guidelines it has been necessary to angle the outermost sensors on each side.

Host Vehicle:

The GLP system is installed in a standard vehicle. Original vehicle, with the integral safety maintained. The driver or passenger may operate the system, as it is controlled from the front seat. Accuracy of measurements is not dependant on the type of vehicular platform utilised.

Each profilograph contains 13 or 15 lasers as well as 3 accelerometers and 2 gyroscopes, which will record all road geometry (cross fall Superelevation, radius of curvature and vertical and horizontal displacement measurements). The captured data is stored on Lacie external hard drive during the survey on a stand alone computer with “real time” displays.

Roughness

Road Roughness is an attribute of the road surface which can be derived from either the physical or mathematical transform of the longitudinal road profile of each wheelpath presented in terms of both International Roughness Index (IRI) and NAASRA Roughness Meter Counts (nrm) for the lane.

Physical transforms can be provided by response-type devices like the NAASRA Roughness Meter. Mathematical transforms apply a vehicular model to the measured longitudinal profile.

Rutting

Rutting is used as a measure of the transverse profile of the pavement surface to give an indication of the surface and structural condition. Rutting also provides a link to road safety. The main use of rutting is at a road safety level where the depth of the rut can indicate potential aquaplaning problems which are generally expected where observed rutting is in excess of 10 mm. The GLP is capable of measuring a maximum transverse profile width of 3 metres. To achieve this, 15 laser sensors are mounted across the front of the vehicle.

Rutting will be measured continuously over the entire length of the segment. This data will be consolidated to 20m intervals to produce an average rut depth and millimetres for left and right-hand wheel paths. Anomalies will be excluded in the production of a mean rut depth and standard deviation for the left and right wheel path of the entire section.

Texture

Pavement texture has major effect on tyre/road noise emission, tyre/road friction, rolling resistance, tyre wear and other vehicle user costs.

International ISO Standard

A standardized method for pavement surface texture assessment has been developed. The draft ISO standard, ISO/DIS 13473; Characterization of Pavement Texture Utilizing Surface Profiles, Determination of Mean Profile Depth.

The GLP provides a robust high-performance system capable of recording macro texture at normal driving speed. All 15 laser sensors are capable of recording the texture measurements simultaneously.

The Greenwood Laser Profilograph (GLP) offers the ability to collect pavement texture depth in the surface by both mean profile depth (MPD) and Equivalent Sand Patch diameter.

This data can be collected simultaneously with Roughness or Rut Depth data, except that 64KHz lasers replace standard 16KHz lasers in position in both wheel paths. The only additional costs associated with producing this data is processing costs to provide certain data formats.

Road Geometry

The Greenwood Laser Profilograph is also capable of producing road geometry data in terms of:

Gradient (%)
Curvature (m)
Cross fall (%)