🏗️ Longitudinal evenness of a pavement — measurement of the profile with a laser profilograph and determination of the IRI

Construction PN-EN 13036-6

Overview

The standard specifies methods of measuring transverse and longitudinal profiles of a pavement in the evenness and megatexture wavelength ranges. It defines the concepts needed to describe such a measurement: the accuracy of the distance travelled, the vertical resolution, the sampling interval and the cross fall, and also a classification of the measuring equipment.

Longitudinal evenness makes it possible to identify deviations of the carriageway surface from a truly plane one, measured along the direction of travel in the wavelength range from 0.05 m to 50.00 m. It is a performance characteristic describing the ability of the pavement not to induce shocks and vibrations in a moving vehicle.

In Polish road practice two measuring routes are distinguished. The profilometric method is based on the IRI indices and is required for the assessment of roads of classes A, S, GP and G, and recommended also for classes Z, L and D. The method of continuous measurement equivalent to the use of a 4 m straightedge and a wedge, for example with a planograph, is permitted for roads of classes Z, L and D and for squares and parking bays; in places inaccessible to the planograph and on sections with bridge expansion joints, measurement with a straightedge and a wedge is permitted. With a laser profilograph the simultaneous recording of the faulting of concrete slabs is possible — faults of a value equal to or greater than 5 mm are recorded together with their location.

The IRI characterises riding comfort by simulating the working of the suspension of a notional vehicle travelling at a speed of 80 km/h over the length of the section analysed. It is given in units of slope: millimetres per metre or metres per kilometre.

WHAT THIS STANDARD DOES NOT CONTAIN — and this is decisive for citing it correctly in a test report. PN-EN 13036-6 describes the MEASUREMENT OF THE PROFILE and lays down technical requirements for the sensors of the profilograph; it contains neither the algorithm for calculating the IRI nor the procedure for recording the faulting of concrete slabs. The national guidelines name separate documents for these two things: the IRI indices are determined „zgodnie z procedurą obliczeniową według normy [4]" [in accordance with the computing procedure of standard [4]], that is ASTM E1926-08 (Standard Practice for Computing International Roughness Index of Roads from Longitudinal Profile Measurements), and the recording of the faulting of slabs is done during the profile measurement „według algorytmu z normy [1]" [according to the algorithm of standard [1]], that is AASHTO R 36-04 (Standard Practice for Evaluating Faulting of Concrete Pavements). PN-EN 13036-6 appears in the same list only as item [8] and is cited solely where the technical requirements for the sensors are concerned. A laboratory which gives in its test report the number PN-EN 13036-6 alone beside an IRI result or beside a list of faults will be citing a document which does not describe those calculations. We did not have the texts of ASTM E1926-08 or AASHTO R 36-04 — we do not reproduce their content here, we merely indicate that they are the documents proper to the calculations.

Method principle

The profilograph is an inertial device: accelerometers monitor the vertical displacement of the measuring beam along the measuring path, establishing the reference line in relation to which the unevennesses of the carriageway are measured. The relative height of the beam above the surface is measured by laser sensors, and the distance travelled by a distance sensor mounted on a wheel. The ordinates of the longitudinal profile along the section are obtained by summing the displacement of the beam calculated from the accelerometer measurement and the corresponding relative height of the beam above the pavement measured by the laser. From the profile thus determined the computing program calculates the IRI indices in accordance with the computing procedure of the proper standard, continuously with a sampling step of 25 mm, simultaneously for the right wheel track, the left wheel track and the centre of the traffic lane.

Applications

• Acceptance of new and resurfaced pavements on roads of classes A, S, GP and G
• Diagnosis of the condition of pavements in a road network
• Assessment of the evenness of squares and parking bays by the straightedge and wedge method
• Recording of the faulting of concrete slabs during the measurement of the longitudinal profile
• Comparative testing of profilographs and checking their correctness

Key parameters

Standard

Standard number

PN-EN 13036-6:2008

Title (PL)

Właściwości nawierzchni drogowych i lotniskowych — Metody badań — Część 6: Pomiary poprzecznych i podłużnych profili w zakresie długości fali równości i megatekstury

Title (EN)

Road and airfield surface characteristics — Test methods — Part 6: Measurement of transverse and longitudinal profiles in the evenness and megatexture wavelength ranges

Step-by-step procedure

1. Choice of method

   For roads of classes A, S, GP and G apply the profilometric method based on the IRI indices; for classes Z, L and D it is recommended, but the method of continuous measurement equivalent to the straightedge and the wedge is also admissible. For squares and parking bays the planograph method is admissible.

2. Checking the equipment

   Confirm that the sensors of the profilograph meet the requirements: vertical resolution of the laser sensor not greater than 0.2 mm, sampling interval of the signal not greater than 50 mm, interval of recording the ordinates not greater than 100 mm, long-wave filter not less than 100 m at a 3 dB drop.

3. Preparing the run

   Plan the measuring path and the speed of the run in the range from 20 km/h to 100 km/h, corresponding to the speed of the traffic flow.

4. Recording the location

   During the test record the data on the location of the measuring path by giving the chainage or the reference system and the geographical coordinates.

5. Measuring the profile

   Carry out a continuous measurement of the longitudinal profile: the laser sensors measure the relative height of the beam above the pavement, the accelerometers establish the vertical displacement of the beam, and the distance sensor the distance travelled. The ordinates of the profile arise from the summing of both components.

6. Calculating the IRI indices

   Determine the IRI indices with a verified computing program, with a sampling step of 25 mm, simultaneously for the right and left wheel tracks and the centre of the lane. NOTE: the computing procedure is NOT given by PN-EN 13036-6 — the national guidelines refer here to ASTM E1926-08, and it is that document which is to be cited in the test report beside the IRI result.

7. Recording the results

   Record in the measurement file the values of the IRI indices every 1 m and the heights of the faulting of concrete slabs equal to or greater than 5 mm together with their location. NOTE: the recording of faulting is done according to the algorithm of AASHTO R 36-04 and not according to PN-EN 13036-6.

8. Test report

   Give the measuring method, the class of the profilograph and the fulfilment of the equipment requirements, the speed of the run, the location of the section, the values of the IRI indices together with the way they were averaged, and the faulting recorded.

Required equipment and apparatus

Health and safety (OHS)

• The measurement takes place in traffic at the speed of the traffic flow — a traffic management scheme for the duration of the test and marking of the measuring vehicle are obligatory
• Laser sensors on the measuring beam — do not look into the beam, take care during calibration at a standstill
• The measuring beam projects in front of the vehicle — a risk of collision when manoeuvring and of damage to the sensors on obstacles in the terrain
• Measurements with a straightedge and a wedge are made on foot on the carriageway — a high-visibility vest, protection of the working place
• Work at bridge expansion joints and on structures — protection against falling from a height

Frequently asked questions