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The Idiots' Guide to Highways Maintenance
Copyright © 2000/14, C.J.Summers

THIS IS A GUIDE TO THE SKID RESISTANCE OF HIGHWAY SURFACES AND SURFACING,
PRESENTED AS INDIVIDUAL ITEMS OF INFORMATION, AND SOME "HISTORY"

Subject Title and Information Relevant to that Title
(To find information on a particular subject use the "find" function of your  "browser" and appropriate key words.)

ANTI SKID SURFACING - HIGH FRICTION SURFACING - HAPAS APPROVAL


The term ANTI SKID SURFACING is usually taken to mean the road surface treatments that include CALCINED BAUXITE as the high PSV aggregate, and a resin rather than bitumen to hold the aggregate to the road surface.
It is generally recognised that ANTI SKID SURFACING / HIGH FRICTION SURFACING should have a minimum SKID RESISTANCE VALUE (SRV) of 70.
There are two main types of anti skid (high friction) surfacing:-

Cold applied processes such as "Shellgrip" and similar named processes, using epoxy resin, or increasingly a polyurethane resin, these are thermosetting resins. 
They are supplied as separate components that when mixed together undergo a chemical reaction producing some heat and setting hard after a number of hours.
The term "Shellgrip" is often used to describe all high friction surfacings, so be very careful when using this term in its broad meaning.

The second type of surface treatment is a hot applied process.
The CALCINED BAUXITE and the resin (in granular form) are supplied premixed in poly bags, the resin in this case is a thermoplastic resin, so the material is heated in a boiler and screeded out onto the road surface whilst it is hot, using a 300mm. wide bottomless "shoe".

Pictures of the two processes can be seen by pressing, -------------------------------------------------------------->
HERE


For general information on HAPAS (Highway Authority Product Approval Scheme), press, --------> HERE

For motorway and trunk road use these materials now need HAPAS approval, but as yet this is not a requirement for local authority work. 

In my opinion the fact that the process of a particular contractor does not have HAPAS certification does not necessarily mean it is a lower quality product. Good quality none HAPAS certified products are often provided by smaller contractors who do not have the funds available to meet the expense of going through the process to gain certification/approval for the amount of work they perform in relation to the larger companies.

Possession of HAPAS certification approval does not mean all the products offered are of equal quality, it only means they have all met a certain basic standard, some products will be better than others, you have to read the small print.



CALCINED BAUXITE - HIGH PSV AGGREGATE - SKID RESISTANCE - HIGH FRICTION - DENSITY


CALCINED BAUXITE is produced by heating BAUXITE rich earth/clays to a very high temperature, approximately 1600 deg. C.
It exhibits very high PSV's and very low AAV's, although the PSV does alter according to the source of the CALCINED BAUXITE.
CALCINED BAUXITE is the aggregate used in the "SHELLGRIP" process. i.e. the high skid resistant surface treatment used approaching Pelican Crossings and other high risk sites.
The density of CALCINED BAUXITE varies from 2.6 to 3.4 according to source, and is an excellent indication of the the PSV of the CALCINED BAUXITE, high density indicates a high PSV.
Guyanan Bauxite (dark grey) has a PSV of approx. 72, and Chinese Bauxite (buff/creamy colour) an approx. PSV of 67.
There are several sources of CALCINED BAUXITE on the market, do not assume this material has a high PSV just because it is CALCINED BAUXITE, ask for test certificates, if the material the contractor is using has a high PSV he will not hesitate in producing certification to that effect.



COLOURED ANTI SKID SURFACINGS - CALCINED BAUXITE

COLOURED ANTI SKID SURFACINGS are now widely available, there are a number of products on the market.
One type I am aware of at present consists of a pigmented polyurethane resin and a surface pigmented CALCINED BAUXITE which is applied to the resin coated road surface.
The resin is a cold applied product, the resin comes as three separate items, resin, hardener and a pigmented filler.
The components are mixed together quite easily in a large container with an electric hand paddle mixer.
When mixed the resin is squeegeed on to the road surface and the calcined bauxite spread on to it.
The resin will hold its colour quite well, but will fade with time.

But the surface pigmentation on the CALCINED BAUXITE tends to wear off very, very quickly with trafficking, the natural colouration of the particular CALCINED BAUXITE showing through, be aware of the above factors when buying/specifying these materials and processes.



CSS ENG/3-95 : The Achievement of Skidding Characteristics for Road Pavements;
Volume 2 - PSV values for Aggregate in UK Roads


This report is Volume 2 of a fairly comprehensive discussion document on many aspects of skid resistance in relation to road surfaces.
The volume consists of a number of information sheets of PSV and other aggregate qualities of the main producers of high PSV aggregate in the UK.


 

CSS ENG/7-94 - SKIDDING RESISTANCE OF ROADS - EFFECTIVE PSV - AAV


The report is Vol.1 of a comprehensive discussion document on many aspects of skid resistance in relation to road surfaces.
The "new" term EFFECTIVE PSV is mentioned, i.e. modifying laboratory found PSV's by a plus or minus factor in view of on site SRV results.
It includes sections on aggregates, polished stone values (PSV), aggregate abrasion values (AAV), road surfacing materials including surface dressing and new "thin wearing courses".
It also discusses methods of testing for PSV of aggregate, and skid resistance value of road surfaces, also ways of categorising road surface needs are suggested.



DTP ADVICE NOTE HA 36/87 - SKIDDING RESISTANCE


This ADVICE NOTE relates to the SKIDDING RESISTANCE of in-service trunk roads, and DTP STANDARD HD 15/87 is the standard which this "advice note" gives advice upon.
This advice note has been replaced by DTP ADVICE NOTE HA 36/93 which was subsequently superseded by DTP DESIGN MANUAL HD 28/94, and the current document is HD 28/04.



DTP ADVICE NOTE HA 36/93 - SKID RESISTANCE - SCRIM


This Advice Note complements Departmental Standard HD 15/93 giving an introduction to the subject of SKIDDING RESISTANCE, advice on risk rating, site investigation and accident analysis.
It discusses the categories and limitations of the SCRIM survey.
Although it may still be quoted it has been superseded by DTP DESIGN MANUAL HD 28/94, and HD 28/04, however it is still excellent background reading if you can obtain a copy.



DTP ADVICE NOTE HA 45/92 - PSV'S, - SKID RESISTANCE


This is the accompanying Advice Note to DTP STANDARD HD 21/92, although this may still be quoted it has been superseded by DTP DESIGN MANUAL HD 28/94, and HD 28/04.


DTP DESIGN MANUAL HD 28/04 - SKID RESISTANCE 

Past editions of this standard used to define specification requirements for POLISHED STONE VALUES and AGGREGATE ABRASION VALUES for new bituminous surfacings, including resurfacing and surface dressing, for trunk roads. 
But this function and associated tables are now included in HD 36/99
This standard supersedes/updates HD 21/92 which superseded HD 16/76, but much of the information is similar.
This section of VOLUME 7 of the DESIGN MANUAL gives good information on the nature of SKID RESISTANCE, skid resistance of roads and means of assessing skid resistance, and related skid resistance surveys / investigation levels.



DTP DESIGN MANUAL HD 36/99 - PSV - SKID RESISTANCE - PERMITTED BITUMINOUS SURFACING MATERIALS - TYRE NOISE


HD 36/99 defines specification requirements for POLISHED STONE VALUES and AGGREGATE ABRASION VALUES for new bituminous surfacings, including resurfacing and surface dressing, for trunk roads.
This standard supersedes/updates parts of HD 28/94 which superseded HD 21/92 which superseded HD 16/76, although much reference to skid resistance remained in HD 28/94, and its successor HD 28/04.
It includes tables of permitted surfacing materials with reference to other design manuals where further information can be found on these materials.
HD 36/99 also has a section on tyre noise.
This section of Volume 7 of the DESIGN MANUAL gives good information on the nature of SKID RESISTANCE, PSV's, AAV's, skid resistance of roads and means of assessing skid resistance, and the related skid resistance surveys/investigation levels.



DTP STANDARD HD 15/87 - SKIDDING RESISTANCE


This standard relates to the SKIDDING RESISTANCE of in-service trunk roads, and advises minimum SRV's for particular sites and traffic conditions.
DTP ADVICE NOTE HA 36/87 is the related "advice note" to this standard, and although now superseded it is excellent background reading on the subject of SKIDDING RESISTANCE if you can still get hold of a copy.
This standard was superseded by DTP STANDARD HD 15/93, which in turn was superseded by DTP DESIGN MANUAL HD 28/94, and then HD 28/04.



DTP STANDARD HD 15/93 - SKIDDING RESISTANCE


This standard relates to the SKIDDING RESISTANCE of in-service trunk roads, and advises minimum SRV's for particular sites and traffic conditions.
DTP ADVICE NOTE HA 36/93 is the related "advice note" to this standard.
This standard superseded DTP STANDARD HD 15/87, and was itself superseded by DTP DESIGN MANUAL HD 28/94, and  the current edition is HD 28/04.


DTP STANDARD HD 21/92 - PSV - AAV - SKID RESISTANCE


This standard defined specification requirements for POLISHED STONE VALUES and AGGREGATE ABRASION VALUES for new bituminous surfacings, including resurfacing and surface dressing, for trunk roads.
This standard superseded /updated HD 16/76, and was in turn superseded by DTP DESIGN MANUAL HD 28/94, TABLE 2:1.
However HD 36/99 now defines specification requirements for POLISHED STONE VALUES and AGGREGATE ABRASION VALUES for new bituminous surfacings, including resurfacing and surface dressing, for trunk roads.
There was an accompanying Advice Note :-
DTP ADVICE NOTE HA 45/92, Advice on aggregate properties for new bituminous surfacings. 
This Advice Note gave good background information on PSV's, AAV's, skid resistance of roads and means of assessing skid resistance, if you are able to obtain a copy.



DTP TECH MEMO H16/76 - PSV - AAV - SKID RESISTANCE


This Technical Memorandum laid down the requirements for aggregate properties and texture depth for bituminous surfacings to new motorway and trunk road construction to match SKIDDING RESISTANCE with different categories of highway layout and traffic flow.
It supplemented the D.O.T. Specification for Road and Bridge Works (1976 edition) and was replaced by DTP STANDARD HD 21/92, which was replaced by DTP DESIGN MANUAL HD 28/94. and now HD 28/04.
DTP STANDARD 21/92 was supported by DTP ADVICE NOTE HA 45/92.
It is now HD 36/99 that defines specification requirements for POLISHED STONE VALUES and AGGREGATE ABRASION VALUES for new bituminous surfacings, including resurfacing and surface dressing, for trunk roads.

It is also worth noting that D.Tp. Departmental Standard HD 15/87 and D.Tp. Advice Note HA 36/87 used to deal with "Skidding Resistance of In-Service Trunk Roads", and it is good reading on this subject.


EFFECTIVE POLISHED STONE VALUE - PSV - SKIDDING RESISTANCE


There is a body of opinion within the industry that wants to have actual laboratory established PSV's for an aggregate amended according to how they perform in service.
i.e. what SKID RESISTANCE VALUE "they" believe that aggregate will provide on the road surface.
This could be an amendment up or down to the laboratory figure.
I personally feel there are so many other factors that contribute to the SRV of a road surface that this would be a very difficult attribute of an aggregate to assess objectively.



GOOD BOOKS ON SKID RESISTANCE


These include:-
Department of Transport, (DTP), Highway Design Standard HD 15/93, and DTP Advice Note HA 36/93,
Skidding Resistance of in Service Trunk Roads, NOW UPDATED to DTP Design Manual HD 28/94.

The booklet "Guidance Note on Surface Dressing Aggregates" produced by the ROAD SURFACE DRESSING ASSOCIATION is a very useful little booklet on aggregate properties, their relation to SKID RESISTANCE, and how to test for these properties.

The book, "Road Aggregates and Skidding" by Roger Hosking issued by TRL and available from HMSO is an excellent book with much good advice on the subject.



GRIPTESTER - SKID RESISTANCE TESTING


The GRIPTESTER is a device for testing the SKID RESISTANCE of road surfaces.
It is a three wheeled machine that is towed behind a suitable vehicle.
It is not large, approximately 1 metre long by 60cms. Wide.
Water is needed to be supplied to the test wheel as all SKID RESISTANCE VALUES relate to a wet road surface.
The 2 "driving" wheels are on a single axle, the "driving" force from this axle is connected to the test wheel but is geared down so the test wheel must rotate more slowly than the "driving" wheels, so creating a braking force on the test wheel.
The braking force can be measured as strain in the wheel axle, this is measured electronically and processed into a GRIP NUMBER (GN).
The braking force felt by the test wheel will be dependent on the SKID RESISTANCE of the road surface.
With recent development and modifications the GN for a road surface is now very similar to the SFC measured by SCRIM.



BS 7941-2 : 2000 : Surface friction of pavements - 
Part 2 : Test method for measurement of surface skid resistance using the GripTester braked wheel fixed slip device


HAPAS - HIGHWAY AUTHORITIES PRODUCT APPROVAL SCHEME - BBA - HiTAC -SKID RESISTANCE - THIN SURFACING


This is a recently introduced organisation to "approve" new products for use in highway maintenance and construction, so that individual authorities do not need to undertake their own trials.

It has been set up by the Highways Agency (HA), CSS (formerly the County Surveyors Society) and the British Board of Agrément (BBA).

I will reserve judgment until I know how materials and processes gain approval / certification, and until I do I am naturally suspicious about this type of "national" approval without any local input.

The development of HAPAS is administered by the BBA, closely advised by the Highways Technical Advisory Committee (HiTAC), certificates of approval are issued by the BBA acting on recommendations from HiTAC.

Specialist groups, with a strong industry representation, are created for each product type.
Products and processes are put forward for consideration by the group who will report back its findings to HiTAC, who will in its turn make recommendations to the BBA as to whether the product / process should receive HAPAS approval.

Full details of the particular schemes and the criteria for assessment are available from :-
British Board of Agrément.

At this date I am only aware of some High Friction Surfacing products having HAPAS approval.
THIN SURFACINGS will soon be able to be HAPAS approved, replacing Highways Agency approval, but approvals seem to be continually delayed for various reasons.


TRL Report 367 : High and low speed skidding resistance : the influence of texture

This report describes the use of the pavement friction tester (PFT).

The PFT was developed in the United States where it is the standard equipment for measuring road surface friction.
It uses the locked-wheel principle to measure the friction, in accordance with ASTM Standard E274, (1990).
The PFT is a towed trailer with both wheels having hydraulically applied disc brakes which are activated by a compressed air system.
On a machine used in the U.K. only the left side wheel is fitted out as a test wheel.



PORTABLE SKID RESISTANCE TESTER - SRV - TRL ROAD NOTE 27


This apparatus is also known as the "PENDULUM TESTER",
The PORTABLE SKID RESISTANCE TESTER is fully described in ROAD NOTE 27.
The PORTABLE SKID RESISTANCE TESTER is used in determining the SKID RESISTANCE of a road surface, and the procedure is also fully described in ROAD NOTE 27, the figure achieved from this test will be the SKID RESISTANCE VALUE (SRV) of the road surface.

When used in the laboratory on prepared aggregate samples the apparatus will establish the POLISHED STONE VALUE, (PSV) of the aggregate.


BS EN 13036-4 : 2003 : Road and airfield surface characteristics - Test methods - 
Part 4 : Method for measurement of slip/skid resistance of a surface - The pendulum test



PSV LISTING - SKID RESISTANCE


This is a guide
to PSV's of various suppliers of aggregate who supply 20mm. PRECOATS, SURFACE SURFACE DRESSING CHIPPINGS and HIGH FRICTION AGGREGATE for wearing course surfaces:-

Calcined Bauxite:- (Guyanan-72), (Chinese-65)

NaturalAggregates :-
Gelligaer-69
Haford-69
White Mountain-67
Craig-Yr-Hesg-68
Gilfach-68
Ghyll Scaur (Millom)-67
Callow Hill-67
Hendre Quarries, Tonnfannau-64
Criggion-62
Bayston Hill-65
Ingleton-61
Gore-63
Cromhall-62
Dry Rigg-62
Dolyhir,Nash Rocks-60
Triscombe-60
Builth Wells-59
Llanwen Slag-55

These are just a few "numbers" I have built up over the years from various sources, the are a guide, some quarries may not even be producing now, others may have moved into other rock areas of the quarry and the aggregate properties may have changed.
So.
Remember you need individual certification of PSV of supplied chippings, you do not accept the figures given here, they are meant only to be an indication of what you might reasonably expect from this source.
It is usual to ask for three sets of PSV results for the aggregate in question from a NAMAS'd laboratory taken within the last six months.

Coloured Aggregate :- Harden Red-54


RASC - RSG - CALCINED BAUXITE - HIGH PSV AGGREGATE - SKID RESISTANCE

RASC is a description of the premium grade of CALCINED BAUXITE available, it is short for REFRACTORY AGGREGATE SUPER-CALCINED, this grade provides the highest PSV aggregate.
RSG when applied to CALCINED BAUXITE refers to ROAD SURFACING GRADE.



RETEXTURING - SKID RESISTANCE IMPROVEMENT

These are physical processes that will restore a texture to sound surfaces that have become smooth through wear.

One type of retexturing machine retextures by impacting the aggregate in the road surface with numerous small hardened steel hammers (often referred to as "bush hammering") to roughen the aggregate surface
Another machine impacts the road surface with free moving rotating roughened discs mounted on a revolving drum.

Although the texture can be improved with these processes it must be remembered that the PSV of the aggregate will remain the same.

An improvement in SKID RESISTANCE VALUE of the road surface is NOT to be confused with PSV value of the aggregate, the PSV of an aggregate cannot be improved, it is what it is !

There are various contractors in the country able to provide machinery capable of this type of RETEXTURING process, both large lorry mounted and small hand operated units.

Further information on these processes is contained in :-


"Volume 7" of the Design Manual for Roads and Bridges (DMRB), in particular, HD 37/99, in Part 2 of Section 5.
The DMRB is now able to be accessed on the "web", a link to it is to be found on the Links Page of this site.

TRL Report 298 : Mechanical retexturing of roads : A study of processes and early-life performance.

TRL Report 299 : Mechanical retexturing of roads : An experiment to assess durability.


ROAD AGGREGATES AND SKIDDING - GOOD BOOKS - PSV - SRV

ROAD AGGREGATES AND SKIDDING, by Roger Hosking,
THIS is an excellent book on the subject of skidding resistance of road surfaces and I recommend it to anyone wanting information on this subject.
The book is published by the Transport and Research Laboratory and is available from :-
H.M.S.O..
The book reference is :- ISBN 011 551115 6


SCRIM - SKID RESISTANCE TESTING

SCRIM is short for SIDEWAY-FORCE COEFFICIENT ROUTINE INVESTIGATION MACHINE.
This machine has been developed to utilise the sideway-force developed on a smooth tyred test wheel, under constant vertical load, angled at 20 deg. to direction of travel, to look at, the SCRIM resembles a "water tanker".
This is because all measurements are taken on a wet road surface, and water is fed at a constant rate on to the road in front of the angled wheel.
SFC varies with speed of the machine, so SCRIM is normally operated at a standard speed of 50 km/h.
Also SFC's vary with the time of the year they are taken, so it is best practice to make three SCRIM runs between May to Sept. and compute a MEAN SUMMER SIDEWAY-FORCE COEFFICIENT (MSSFC).



BS 7941-1 : 1999 : Methods for measuring the skid resistance of pavement surfaces
Part 1 : Side-way force coefficient routine investigation machine


SHELLGRIP - ANTI SKID SURFACING - HIGH FRICTION SURFACING

SHELLGRIP is the trade name for a resin based high skid resistant road surface treatment, using CALCINED BAUXITE as the aggregate.
However the term "shellgrip" has come to be used for similar processes offered by other suppliers just like the words 'biro" or "hoover".
The "SHELLGRIP" process is specified and described in :-
The D.0.T. Specification for Highway Works, ( WHITE BOOK) : 1994 : Clause 924:Resin-Based High Skid Resistant Surface Treatment.
The above clause describes in detail the "shellgrip" process and sets down specifications for the materials used, basically epoxy resin is sprayed onto the road surface, then calcined bauxite is applied to the resin at the appropriate rate on curing the resin will bond to the road surface and hold the CALCINED BAUXITE firmly.

The most recent edition of the S.H.W. defers the specification of HIGH FRICTION SURFACING to HAPAS.



SIDEWAY FORCE COEFFICIENT - SFC - SKID RESISTANCE - SCRIM

The abbreviation "SFC" stands for :- SIDEWAY-FORCE COEFFICIENT,
This is the value of the skidding resistance of a road surface obtained using the SIDEWAY-FORCE COEFFICIENT ROUTINE INVESTIGATION MACHINE, (SCRIM).
BE VERY CAREFUL with terminology. SFC's are NOT quite the same as SKID RESISTANCE VALUE (SRV), they are almost the same BUT not quite.
The SRV is obtained from the use of the PORTABLE SKID RESISTANCE TESTER.
Another abbreviation you will come across is MSSFC, this stands for:-
MEAN SUMMER SIDEWAY-FORCE COEFFICIENT.
It is normal practice to make three SCRIM runs from MAY to SEPTEMBER and compute a mean summer value hence MSSFC.


SKID RESISTANCE VALUE - SRV

The SKID RESISTANCE VALUE of a road surface is just what the phrase suggests, i.e. the ability of the road surface to resist kidding.
It is a combination of the SURFACE TEXTURE of the road surface and the P.S.V. of the aggregate in the road surface.
SURFACE TEXTURE of the road surface is often referred to as MACRO TEXTURE.
Texture actually on the surface of the aggregate is known as MICRO TEXTURE.
The SKID RESISTANCE VALUE (SRV) is measured using the PORTABLE SKID RESISTANCE TESTER or the SCRIM.
Minimum SRV's for various road sites are now quoted in D.Tp.Advice Notes.
The SIDEWAY-FORCE COEFFICIENT ROUTINE INVESTIGATION MACHINE (SCRIM) speedily records on site SIDEWAY FORCE COEFFICIENT (SFC) values on a complete road survey.
S.F.C. values are very similar to, but NOT the same as S.R.V.'s.


 NEW !  TEXTURE DEPTH OF ROAD SURFACE - SERIES 900 : Clause 921 : Surface Macro Texture 0f Bituminous Surface Courses,
Manual of Contract Document for Highway Works : Volume 1 : Specification for Highway Works

This is a complete revised 900 Series of the Specification, MCHW1 for Road Pavements -Bituminous Bound Materials.
It has been introduced to coincide with the publication of the new European Standards for bituminous mixtures
BS EN 13108 family of standards for Bituminous Mixtures from the 1st.of January 2008. 
The specification has also introduced a number of important changes other than those related to the specifying of bituminous mixtures to BS EN 13108

Click here for further information on road surface skid resistance One of the most important of these changes, which in my opinion is not a "minor revision", is the reduction in initial texture depth of "thin surface course systems" (TSCS) on high speed roads, to not less than 1.3mm., and to not less than 1.0mm. on low speed roads and roundabouts on lower speed roads.

I urge you to obtain a copy of the "Amendment - August 2008" of the 900 Series of Volume 1 of the Specification for Highway Works (SHW), it can be download from www.standardsforhighways.co.uk and study, Clause 921-Surface Macrotexture of Bituminous Surface Courses.

In previous editions of the "900 Series" , e.g. November 2004, the figure quoted was the single figure of 1.5mm. for "high speed roads" but with no clear indication of what a high speed road was so the default was 1.5mm.
In the current Clause 921 there is a table containing the minimum texture depth requirements for defined surfacing materials, road speeds and locations.


TRL PROJECT REPORT PR/H/58/93 - SCRIM - GRIPTESTER - SKID RESISTANCE MEASUREMENT COMPARISONS

This report is UNPUBLISHED at 31/12/93.
This Project Report has been prepared for the County Surveyors Society Griptester User Group.
The TRL Test Track was used for comparison of the GRIPTESTER and SCRIM machines.
TRL also analysed the results gained from the test track runs to produce the information in this report.
As this is an UNPUBLISHED report no mention of conclusions drawn will be referred to here, but they are "interesting".
Copies of the report may be obtained only by direct personal application to TRL.



TRL Report 125 : TRL Report 125 - Trials of high-friction surfaces for highways

The report gives information on the performance of the differing systems on the market, epoxy-resin, polyurethane-resin, acrylic-resin and rosin ester, this information being obtained from a series of road trials throughout the U.K..
Laboratory tests have also been devised to simulate accelerated wear under trafficking.



TRL Report 176 : Laboratory tests on high-friction surfaces for highways

A number of laboratory test have been devised to test for the quality of HIGH FRICTION surfacings with the purpose of assessing various materials for having the necessary level of quality to receive HAPAS approval.
This report describes the tests and testing procedures, but does not suggest the levels of performance materials must attain to receive the HAPAS approval / certification.



TRL Report 298 : Mechanical retexturing of roads : A study of processes and early-life performance.


TRL Report 299 : Mechanical retexturing of roads : An experiment to assess durability.


TRL Report 322 : Polished stone value of aggregates and in service skidding resistance


TRL Report 367 : High and low speed skidding resistance : the influence of texture depth


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 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 (2) above is considered in this report.
Point (1) is considered in TRRL REPORT 738



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


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.


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