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  The Idiots' Guide to Highways Maintenance

Copyright 2000/15, C.J.Summers



Bump Integrator

Rolling Straight Edge

Regulating Course / Material


The bump integrator is a piece of apparatus for measuring the riding quality of a road surface.

The apparatus is a single wheel, similar to a large car wheel, which is on an axle contained in a small frame, and forms a small single wheeled trailer.
The apparatus is pulled behind a suitable vehicle with a towing hitch.
The bump integrator has standard leaf springs and "shock absorbers", and is designed to be independent of the vertical movement of the towing vehicle.
The apparatus incorporates a unit known as the "integrator unit" that is capable of detecting downward movement in relation to the frame/chassis.

This accumulated movement is measured as is the distance travelled.
The bump integrator is capable of measuring both surface irregularity and riding quality at normal road speeds and producing a report, which is to supply information to road engineers who wish to use the bump integrator for routine road assessment.

This one of the "simpler", more straight forward, ways of measuring the ride quality of the road surface, and hence detecting potholes in the wheel track.

TRRL SUPPLEMENTARY REPORT 26 UC : Bump-integrator measurement in routine assessment of highway maintenance needs

This report is an extremely comprehensive report on the bump-integrator.
It includes a complete description of the apparatus, details how it works, describes how surface irregularity is measured, and supplies suitable forms for recording the information.

I try to refer to as few commercial sites as possible in compiling my site, but when a site offers particularly useful information about a subject I make an exception.

For further information on the BUMP INTEGRATOR, and other more "sophisticated" equipment for measuring ride quality, press ------>


The rolling straight edge is a piece of apparatus for quickly assessing the surface of a road, or a particular pavement layer, for surface regularity, i.e. no bumps or hollows.

The apparatus is approximately 3 metres long and 25cms. wide and it has a strong aluminium frame to which many wheels are attached at the bottom edge of both sides.
The wheels are attached either side, i.e. two rows of wheels, and these wheels create a moving straight line reference.
Mid way along the length of the apparatus is a wheel that is able to move vertically.

The vertical movement of the test wheel in relation to straight line reference is able to be continuously measured on a dial, visible to the operator, as it is pushed along.

A particular setting of depression measurement is able to be set as a reference, if this setting is exceeded it will cause a bell to ring.
This gives a useful indication of a suspect area that can be checked more accurately by observing the measurement on the dial.

There are specified limits for surface tolerance laid down in the,

D.O.T. Specification for Highway Works, Volume 1, Clause 702 : Methods of measuring surface regularity

and there are tables of permitted tolerance and methods of rectification included in this clause.
The rolling straight edge is a piece of apparatus that must receive official calibration at least once a year at an approved calibrating laboratory for the results to be contractually valid.
But there is nothing to stop you using an accurate but officially uncalibrated machine to indicate suspect areas and then to check these with a 3 metre steel straight edge and measuring "wedge".

The following report tells you all about this piece of equipment,

TRL Report SR 290 : Calibration, maintenance and use of the rolling straight edge


A regulating course as the name suggests is a layer of material to regulate the existing surface level of a road prior to receiving a wearing / running surface, i.e. where the road to receive the surface has bumps and hollows in it that need removing.
It is necessary to do this so that the finished surface will have a good riding quality.

In order that the final surface layer shall be to the designed thickness, and within desired tolerance levels of regularity, the existing surface receives a regulating course of a usually variable thickness of a suitable regulating material to fill in the hollows and place no material on the high spots.

To achieve good and practical regulation you require a material that is capable of being laid quite thinly in places and yet retaining stability at some thickness in the hollows.

If no regulating occurs and the surfacing material, (surface/wearing course), is laid at variable thickness, then on rolling the differing layer thickness will compact more where it has been laid thicker and less where it has been laid thinner.
Therefore the design levels and surface regularity will be lost.


Where the regulation that is required is minimal it is possible to use an amount of the wearing course material as a regulating material rather than having to purchase a small tonnage of regulating material.

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