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  The Idiots' Guide to Highways Maintenance

Copyright 2000/16, C.J.Summers


There are reports prefixed TRRL and not those prefixed TRL , this is due to a name change from the Transport and Road Research Laboratory to the Transport Research Laboratory.

The TRRL reports are earlier than the TRL reports, and reference to
TRL reports can be found on a separate page.

The TRL website address is www.trl.co.uk, and information relating to most TRRL/TRL reports can be found there even if some of the older ones are difficult to track down.


If you register with TRL, on their website, you are able to download, at no charge, complete copies of most of the various TRL and TRRL reports, in .pdf format.
I found that  locating a particular report that you are looking for can sometimes be a bit tricky, so I recommend several attempts using appropriate key words before giving up, and at this time I have yet failed to download a report that I required..
This is an almost unbelievable access to a huge amount, and depth, of information relating to the total subject of highways, and in relation to this website the subject of highways maintenance.

But before you rush off to the excellent TRL website it will probably help you to have a browse through this page where you may well find a little extra information relevant to a particular report and the subject it covers.

To find specific information in this page please use your browser "find" function to perform a search using an appropriate keyword or words.

NEW - This list of TRRL publications can be downoaded in .pdf format for easy browsing off line.

TRRL - TRRL stands for Transport and Road Research Laboratory

Ownership of the Transport Research Laboratory was transferred from the Department for Transport to a subsidiary of the Transport Research Foundation on the 1st. of April 1996.

The TRANSPORT RESEARCH LABORATORY (TRL)  is now privately owned.

The TRANSPORT RESEARCH FOUNDATION is a company limited by guarantee.
A company limited by guarantee is a company set up where the "members" of the company have a liability limited to the amount set down in the "memorandum of understanding" of the company.
The amount is usually quite small, however I believe the company is still liable to a claim against its assets.

TRL Report Title - With Description / Associated Information

TRRL Application Guide 20 - Fin Drains

TRRL Report 1102 : Compaction of bituminous road materials using vibratory rollers

TRRL Laboratory Report 1132 : The structural design of bituminous roads

The report deals with the design of bituminous roads taking into account the increase in traffic volume and increased weight of vehicles, it replaces Road Note 29.
In addition to "1132" there are various D.Tp.,Highways and Traffic, Design Notes and Advice Notes that supplement the report,
e.g. HD 14/87 Structural Design of New Road Pavements, and AMENDMENT No.1 to HD 14/87
Also HA 35/87 Structural Design of New Road Pavements

See also:-
DTP DESIGN MANUAL FOR ROAD AND BRIDGES, VOL 7, this design manual includes many new individual Design Guides that supercede their older versions, many of which I have left reference to in this database.

TRRL Report 571 - Deflectograph - An overall view

TRRL Report 612 : Continuously reinforced concrete pavements : a report of the study group.

This is an excellent study, giving good information on this type of carriageway.

TRRL Report 693 : Aggregates for High Skid Resistant Roads

This is a report reviewing the properties of aggregates as potential sources of high skid resistant aggregate.
It pays particular attention to CALCINED BAUXITE.

TRRL Report 737 - Guide to use of SCRIM - Skid Resistance

This report outlines the basic principles underlying the design of SCRIM, describes the vehicle, test wheel, recording system and water supply, and discusses ways in which the results can be analysed.

TRRL Report 738 - SCRIM - Road Slipperiness Factors - Skid Resistance

Skid resistance measurement is affected by two classes of factors :-
(1) Factors affecting the slipperiness of the road, such as the state of polish of the surface.
(2) Factors affecting the skidding resistance measurements themselves, such as the accuracy of the calibration of the test instrument.
Point (1) above is considered in this report.
Point (2) is considered in TRRL REPORT 739

TRRL Report 739 - Variations to SCRIM measurement - Skid Resistance

Skid resistance measurement is affected by two classes of factors :-
(1) Factors affecting the slipperiness of the road, such asthe state of polish of the surface.
(2) Factors affecting the skidding resistance measurements themselves, such as the accuracy of the calibration of the test instrument.
Point (2) above is considered in this report.
Point (1) is considerd in TRRL REPORT 738

TRRL Report 833 -Prediction of Performance and the Design of Overlays
(and that briefly and accurately sums it up)

It is too involved to attempt description in a few words, but this report provides information in graph and table form.
It is this information converted into computer programmes that allows the DEFLECTOGRAPH SURVEY that we are now familiar with to take place.
If you are involved with, or need to know about DEFLECTOGRAPH SURVEY work read this report and the reports, TRRL REPORT 834 and TRRL REPORT 835.

There are 4 variables with deflectograph,
(1) temperature of road
(2) core classification
(3) calibration accuracy of the machine
(4) traffic figures.
Use deflectograph information as a guide, do not be rushed into road maintenance that other factors, e.g. visual appearance, trial holes, do not support.

TRRL Report 834 - Deflectograph - Equipment

This report physically describes the DEFLECTION BEAM and the Lacroix DEFLECTOGRAPH and their respective methods of use.

TRRL Report 835 - Deflectograph Operating Procedure

TRRL Report 844 - Estimation of Traffic Flows

This report contains two nomograms which allow the estimation of cumulative one way commercial traffic, one for forward estimation and one for past estimation.
If you need to make these sort of assessments these nomograms can be very useful but perhaps not exactly accurate.

TRRL Report LR 308 : Resistance to cracking of rubberized asphalt : Full-scale experiment on Trunk Road A6 in Leicestershire

This report is a case study of a full scale experiment, the length of road chosen for the experiment was of concrete bay construction, and a BASECOURSE and WEARING COURSE were laid.
4% and 5% of rubber by weight was added to the 50PEN. BITUMEN in the form of rubber latex. The latex itself being 68% dry rubber, it is very interesting to note the BINDER percentage of the WEARING COURSE was also increased by 1% giving quite a rich mix.
The report declared the trial a success, especially the sections with a 75mm. basecourse and 50mm. wearing course.
This road did not suffer abnormal rutting and I suggest anybody considering adding rubber to "dry" DESIGN ASPHALT read this report.

TRRL Report LR 324 - Sulphates in Colliery Shale 

This report covers the effects of sulphates in COLLIERY SHALE relating to its use as a roadmaking material. It suggests limits of sulphate content in shales considered safe in relation to its proximity to concrete structures or concrete products.
The report also discusses other problems that can be encountered with COLLIERY SHALE.

TRRL Report LR 363 : Air entrained concretes : a survey of factors affecting air content and a study of concrete workability

AIR ENTRAINING AGENTS are included in CONCRETE to prevent damage by frost and de-icing salts, in CONCRETE PAVEMENTS.
Also to increase WORKABILITY in STRUCTURAL CONCRETE, it is also claimed to reduce segregation, bleeding and shrinkage of concrete.
This report is a study of factors affecting air content and its affect on CONCRETE, it is an excellent report and recommended reading on this subject.

TRRL Report LR 370 : Full-scale road experiments using rubberized surfacing materials

This report relates to full scale RUBBERIZED BITUMINOUS MATERIAL trials (including HRA) conducted on various sites throughout the country.
This report includes two Leicestershire sites, the A6 Lockington and the A426 Dunton Basset.
The material was laid over roads of concrete bay construction to help prevent reflective cracking from the joints between bays.

TRRL Report LR 375 : Deflection criteria for flexible pavements

This report is a study of the relationship between deflection readings from a deflectograph survey, and the type and condition of the ROAD PAVEMENT and the materials present in the pavement.

TRRL Report LR 381 : Trial of Epoxy/Calcined-Bauxite surface dressing on the A1, Sandy, Bedfordshire, 1968

This report is an early case study of the use of EPOXY RESIN and CALCINED BAUXITE to produce a high SKID RESISTANT surface on the A1 at Sandy in Bedfordshire.

TRRL Report LR 466 - Skid Resistant Surfacings - Calcined Bauxite

This report describes the use of resin bound surfacing systems employing refractory grade-grade calcined bauxite aggregate, although an old report, (1972), most of the information is still relevant.

TRRL Report LR 467 : Synthetic aggregates of high resistance to polishing : Part 2-Corundum-rich aggregates

This report describes a study on aggregates that have a high resistance to polishing, these being mainly CALCINED BAUXITE.
It is an extremely good report for anybody wishing to know more detailed knowledge on the various grades of CALCINED BAUXITE, not all grades of CALCINED BAUXITE are suitable for road surfacing.
The best grade for road surfaces is RASC grade, (refractory grade).
The CALCINED BAUXITES with high specific gravities, i.e. over 3.0 tend to have higher PSV values.

The quantity of CALCINED BAUXITE can be found in a mixed aggregate by using the heavy liquid, 1,2,2, -tetrabromoethane to perform a simple "sink or float" test, as described in this report.

TRRL Report LR 504 : The effect of traffic and aggregate on the skidding resistance of bituminous surfacings

This report was published in 1973, but it is still used as a reference document, it discusses the subject of aggregate polishing and the resulting skid resistance of road surfaces due to traffic volume.

TRRL Report LR 510 : A guide to levels of skidding resistance for roads

This report was published in 1973, but it is still used as a reference document.
It discusses the subject of skid resistance of road surfaces and the factors involved, including skid resistance measurement.
Tables of suggested levels of skid resistance are contained in this report.

TRRL Report PA/SCR243 - Road Haunch Maintenance

This is an extremely comprehensive report on the causes, problems and construction practises associated with HAUNCH WIDENING.
Recommended reading for all, especially those with little or no practical experience of this subject.
It is also available as "A PRACTICAL GUIDE TO HAUNCHING" produced by the County Surveyors Society, cost 5.
It is available from the CSS's Honorary Secretary.
Haunch design, materials, construction methods and compaction information in the above guide is very similar to the information given in the :-
5-95 from H.M.S.O..

TRRL Supplementary Report 323 : A full-scale experiment to compare surfacings for maintaining bituminous roads :A1 Buckden, 1975

This report includes information on:-
Open-textured macadam,
Pervious macadam,
Dense (Close-graded) bitumen macadam,
Hot rolled asphalt,
Surface dressing.

TRRL Supplementary Report 561 : A study of blends of Trinidad Lake Asphalt and bitumen in rolled asphalt.

This is quite a comprehensive report on the nature, properties and uses of TRINIDAD LAKE ASPHALT

TRRL Report SR 573 - Surface Dressing Hardness

This report sets out the procedures for assessing the hardness of road surfaces in respect to surface dressing.
Road hardness and traffic flow / type govern the size of chipping chosen for a particular site.

TRRL Supplementary Report 627 : A guide to road surface dressing practice

This is an excellent, very comprehensive, report on SURFACE DRESSING, it may be a few years old now but is not out of date, and it is recommended reading.

TRRL Report SR 675 : In-situ recycling of asphalt wearing courses in the U.K.

Author G.D.Goodsall
Published 1981

TRRL Report SR 798 : High performamce surface dressing : No. 3, Properties of thermosetting binders related to road performance

TRRL Research Report 122 : The effect of EVA modified bitumens on rolled asphalts containing different fine aggregates

This report covers trials documenting the effect of EVA modified bitumens on hot rolled asphalts containing different fine aggregates.
WELL WORTH READING, if you want some basic information on EVA in HRA, especially HRA wearing courses.

TRRL Research Report 196 - EVA Modified Bitumen Macadam Roadbase (Base)

This report covers trials on the use of EVA as an additive to the bitumen binder in macadam roadbase.
This trial indicated there was no significant benefit in the addition of EVA in roadbase macadam.
Without an improvement in the engineering qualities of the roadbase, hence a reduction in layer thickness, it was suggested the increased production cost is not justified.

TRRL Research Report 267 - Bitumen Permittivity - Dielectric Constant - Texture

This report covers a trial conducted in 1982, and monitored in subsequent years, to study the relationship between the PERMITTIVITY of the BITUMEN and the surface TEXTURE of HOT ROLLED ASPHALT.
Although BITUMENS with a higher PERMITTIVITY did weather to a greater extent than those with a lower PERMITTIVITY and hence create more surface TEXTURE it was NOT significant, within the range 2.6 to 2.7.
It was felt with high STABILITY, and DESIGNED ASPHALTS with high rates of spread of PRECOATS, this has combined to make the development of TEXTURE DEPTH and SKID RESISTANCE independent of BITUMEN PERMITTIVITY.
N.B.:-PERMITTIVITY can also be referred to as DIELECTRIC CONSTANT.

TRRL Report 296 : The relation between the surface texture of roads and accidents

This report is a study in the relationship between the TEXTURE of a road surface and the incidence of accidents.
It supplies good information on such subjects as MICRO TEXTURE, MACRO TEXTURE, the HIGH SPEED TEXTURE METER and SCRIM.
It discusses in some detail the relationship between surface texture, skidding resistance and accidents.

TRRL Report 297 : Measurement of the macro texture of roads : Part 3. Development of the high-speed texture meter

This report covers the design, development and use of the HIGH SPEED TEXTURE METER.
The device uses a contactless (laser) sensor to measure road MACRO TEXTURE.
Similar methods of texture measurement are in the TRRL MINI TEXTURE METER and the HIGH SPEED ROAD MONITOR.

TRRL Research Report 305 - Recycling Bitumen Macadams

This report assesses the performance of off-site recycled bituminous material.
Initial results show that off-site recycling of bituminous materials can be successful when correctly controlled.
Laid sections of recycled material have performed well in trials.
The cost of recycled material may well be more expensive than conventional material.
But the planings MUST be of a consistent analysis for them to be suitable for large scale recycling.
The recent introduction of the Land-Fill Tax has considerably altered the balance in favour of recycling.

TRRL Research Report 323 - Porous Asphalt  - Modified Binders

This report is a comprehensive study on trials conducted on POROUS ASPHALT with differing binders and additives, as well as associated trial areas of HOT ROLLED ASPHALT for comparison purposes.
The trials taking place on the A38 Burton Bypass in November/December 1987.
This report is recommended reading for anybody considering using POROUS ASPHALT, and seeking information on various modified bitumens included in the trial.

The Shell bitumen MULTIPHALTE was included as a binder in the HOT ROLLED ASPHALT trial lengths.

TRRL Research Report 4 : Cooling of bituminous layers and time available for compaction

This is a report on the cooling of bituminous layers, the factors affecting cooling, including wind chill, and the time available for compaction.

In simple terms the thicker the layer the longer it will take the material to cool and the longer time you will have for compaction.
This is especially important with WEARING COURSE layers in winter, i.e. they are thin and cool quickly, and even with thicker layers you can get a "skin" of chilled surface material.
This can be a particular problem with precoated chippings on hot rolled asphalt wearing courses, if the surface of the laid mat chills quickly there will not be enough heat to melt the precoated chipping bitumen coating which bonds it to the bituminous material.
You can even have situations where chippings are pushed into the mat, because underlying material is still hot and plastic, but the precoats have not formed a bond with the wearing course and therefore quickly become removed from the road surface by traffic.
You MUST remember however that thick layers of hot material in hot summer weather can also be a problem because of the length of time it will take to cool.
You may also lose PRECOATS in the HRA WEARING COURSE if you do not control rolling carefully.

TRRL Research Report 56 - Roller Compaction Trials

This report compares the performance of a 9 tonne dead weight roller with a 1.3 tonne (Bomag 75ADL) vibratory roller.
The materials used for the compaction trial were 20mm dense basecourse macadam and 40mm dense roadbase macadam.
At up to 100mm layer thickness achieved densities were comparable,
BUT it is important to compact at higher temperatures for the lighter vibratory roller to perform to its best ability.

TRRL Research Report 90 - Moisture Condition Test - Soil / Fill

The study contained in this report is to determine the precision of the MOISTURE CONDITION TEST, ten laboratories were involved, some difficulties were experienced.

TRRL Supplementary Report 153 UC - CHART

TRRL Supplementary Report 20UC : The use of unburnt colliery shale in road construction

TRRL Supplementary Report 26 UC : Bump-integrator measurement in routine assessment of highway maintenance needs

The BUMP INTEGRATOR is capable of measuring both surface irregularity and riding quality at normal road speeds, and this report is to supply information to engineers who wish to use the BUMP INTEGRATOR for routine road assessment.
It includes a description of the apparatus, how it works, how surface irregularity is measured, and suitable forms for recording the information.
It also includes pictures of the equipment.

TRRL Supplementary Report 522 - Soil Compaction - MCV - MCT

This report details the MOISTURE CONDITION TEST, including diagrams of the MOISTURE CONDITION APPARATUS and blank laboratory test sheets for the recording of results and the working out of the MOISTURE CONDITION VALUE.

N.B. The MOISTURE CONDITION VALUE has no meaning as a stand alone piece of information, it MUST be related to a soil's MOISTURE CONTENT (MC), and the particular engineering qualities of THAT soil at THAT particular MOISTURE CONTENT.
It is necessary to have performed the various "engineering" soil tests, e.g. "optimum dry density", on a soil at a particular MOISTURE CONTENT, and then obtained a MOISTURE CONDITION VALUE at this MOISTURE CONTENT.
Only then will the on site "MCV's" be able to tell you whether the soil meets acceptable engineering criteria for optimum compaction.

TRRL Supplementary Report 550 : Proposed warning levels for the structural maintenance of flexible roads

The report details various warning levels recommended for use in highway maintenance rating systems.

TRRL Supplementary Report SR 754 - Nuclear gauges for measuring density of dense roadbase macadam : report of a working party

TRRL Technical Report 303 - Asphalt Substitution

This report presents road trials that have been carried out to assess the potential for using bituminous materials to replace thicker layers of granular materials in road construction.
It was shown that providing the foundation was strong enough to support construction traffic with negligible deformation then ASPHALT SUBSTITUTION was worth considering.
It is important to stress the subgrade/laying surface MUST be able to take the construction traffic that will be laying the bituminous mixture.
Conventional design with a granular sub-base layer will be able to cope much better with the vagaries of English weather and the softening of subgrades.

TRRL Report 308 : Overlay design for improved macadams

This report describes the possible benefits of using IMPROVED/STIFF MACADAMS, i.e. roadbase and basecourse.
These improved macadams being known as :-
The basic concept behind the use of these materials being that they are much stiffer than conventional macadams and are therefore possess better load spreading properties, meaning thinner layers of material or increased design life.
Increased resistance to rutting is also a possibility with these materials.


This is an old, 1975, publication, it is however an excellent basic document on concrete design, and to be recommended if copies are still available.

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