Conclusiones

9. Roughness Surveys with Bump Integrators

Introduction

Overview

Roughness surveys are used to record the roughness over a sampling interval (default of 100 m), the roughness can be recorded using one or two bump integrators. During the roughness survey additional data can be recorded, such as:

 Visual keyboard rating;

 Location reference points;

 Transverse profile and rut depth;

 GPS measurements;

 Moving traffic survey;

 Travel Time Survey;

Resolution of BI Measurements

The accuracy of the roughness measurements is a function of the precision of the bump integrator (BI).

The ROMDAS BI encoder returns 500⁸ pulses per revolution. With a spindle diameter of 45 mm this corresponds to approximately 3.5 pulses per mm of vertical travel, or a resolution of approximately 0.3 mm.

Roughness Survey Setup Options

Roughness Survey Setup Options

 Auto Reset at Sampling Intervals: Normally, one defines a sampling interval for roughness surveys which is a fixed length (e.g. 100 m). ROMDAS then automatically resets the roughness counts at the end of this sampling interval. However, if you wish to manually reset the roughness at the end of a

8 Bump Integrators supplied before 2008 had 360 pulse per revolution encoders with a resolution of approximately 0.4 mm

sampling interval you would enter “N” here. The resets would then be done by pressing the ESC key.

In practice, this is only done with long sampling intervals, such as 1000 m, and is not normally recommended.

 Roughness Sampling Interval (m): The roughness sampling interval is the regular interval over which to sum the roughness counts. It is recommended that 100 m be used for the minimum sampling interval. Even if data are only required at longer intervals, for example 1000 m, by sampling at short intervals the data can be aggregated upwards. However, if a large sampling interval is used the data cannot be disaggregated downwards. It is not recommended that intervals less than 20 m be used since, particularly on roads with low roughnesses, they can give misleading results.

 BI Minimum Speed Warning. This is the minimum survey speed. If the average speed in the roughness survey over an interval drops below the minimum speed, the computer will beep at the end of the interval.

 Use Roughness Exclusion at Low Speeds. When this option is selected ROMDAS will automatically discard all measurements below the user specified speed and calculate the equivalent roughness. The user must define the speed below which this option is to be implemented.

 Display Calibrated Roughness During Survey. When this option is selected ROMDAS will automatically discard all measurements below the user specified speed and calculate the equivalent roughness. The user must define the speed below which this option is to be implemented.

 Roughness Coefficients for display. Select the appropriate Roughness Calibration Coefficients to display the Calibrated Roughness of the Bump Integrators during the survey.

 Equivalent Roughness on BI Exclusion. During a roughness survey the roughness meter can be temporarily halted. This is used, for example, when travelling over a road in the process of being reconstructed. It can be done either by halting the BI with a keycode event, by pressing the F5 key or with BI Exclusion at Low Speeds settings below (see Chapter 0).

If this option is selected as “Y” ROMDAS will calculate and record the equivalent roughness based on the length measured. Otherwise, ROMDAS will record the actual roughness.

 Distance to Extend Sampling Interval at LRP. When approaching an LRP the situation may arise where the sampling interval may end just in advance of the point where the LRP reset is pressed. This would lead to a short section of data between the end of the sampling interval and the LRP. To avoid this, ROMDAS will extend the last sampling interval before the LRP by the distance specified here.

 Include Measured and LRP Chainages in Roughness table. The Chainages of the LRPs should be baseline values against which all other measurements are referenced. During the roughness survey the

9 Roughness Surveys with Bump Integrators

vehicle is travelling at a speed and even a slight delay in pressing the LRP reset key will lead to an error in the chainage recorded. This option will use the LRP chainage from the LRP file to replace the chainage recorded by the vehicle. By always replacing the recorded Chainages with the LRP file Chainages the data in successive surveys will always have the same start and end Chainages.

ROMDAS will automatically adjust the measurements to these Chainages. This greatly facilitates importing the data into road management systems since the location referencing is the same for each section from year to year. For this reason this option defaults to “Y”.

Executing the Survey

Starting the Survey

Select New Survey menu option and enter the survey data into the Survey Setup screen as per Section 0 and proceed to the Survey screen.

Press the Space Bar to start surveying.

During the Survey

During the survey the roughness will be displayed from each bump integrator, along with the distance travelled. At the end of each roughness interval the total raw BI count and the average speed is displayed.

If keyboard rating is performed during the survey this will be displayed. Above is an example of recording a bridge.

Ending the Survey

At the completion of the survey press the F10 key. See Section 0 for further options when ending the survey.

Example of Data

Roughness Exclusion

Overview

During surveys there are often times when it is desirable to pause the roughness recording (roughness exclusion), for example:

 If there are road works

 On bridges

 Over fords

 At low speeds (below the BI calibration speeds) This can be done in three different ways

 manually by pressing the F5 Manual Roughness Exclusion key

 by associating a keyboard continuous or switch event with Roughness Exclusion during Event (see Section 0 Defining Keyboard Events).

 By setting the Roughness Exclusion at low speeds parameters (see Section 0)

Roughness Exclude Processing Options

There are two options for processing the roughness data when roughness is excluded during a survey:

 Actual Roughness Count: This is the actual roughness recorded over the sampling interval when the measurements were not paused; or,

 Equivalent Roughness Count: This is the roughness over the interval based on the measurements that were actually made.

The equivalent is calculated as follows:

ECOUNT = COUNT * SAMPLEIN / MEASURED

where ECOUNT is the equivalent roughness count in counts/sample interval SAMPLEIN is the sampling interval in m (usually 100 m)

MEASURED is the length of the sampling interval roughnesses were measured over in m For example, if you measured for 70 m out of a 100 m interval and there were 10 counts, the equivalent roughness would be 14.

This option is set under Tools|Options|Roughness Bump Integrators. The default setting is for Equivalent Roughness on Roughness exclusion to be set to Yes (Section 0)