Thin Surfacing in the News
I have recently noticed a correspondence taking place in one of the major engineering journals relating to Thin Surfacing, and whether Thin Surfacing is as good as it is claimed to be in all the advertising and hype that is associated with these bituminous mixtures.
So, I thought I would state a few simple truths, for those following the debate, to think about.

• The term Thin Surfacing relates to proprietary bituminous mixtures (blends of aggregate and bitumen, possibly modified) that are laid less than 40mm. thick as the surface course, they are not "magic" materials.
• There is no such thing as Thin Surfacing, if you are thinking it is one material, there are now many dozens of Thin Surfacings, some sold under different product names from one company, some sold as different types of mixture under the same company brand name.
• Thin Surfacings are laid at differing thickness, generally from 25mm. to 40mm., and this will have a huge bearing on the performance of the mixture.  
• Thin Surfacings are likely to be porous so that the road surface will attain the required 1.5mm. (sand-patch) texture depth.
• HAPAS, the Highways Authority Product Approval Scheme, does not approve individual products as the name implies, it approves "systems" for producing products, and it is possible that the product (bituminous mixture) that you are purchasing has not been through performance trials for that particular mixture. 
  Aggregate source, bitumen source, and even bitumen grade may have been changed from that used in the performance trial.
• It is interesting to note that if you visit the BBA/HAPAS website it states that the "Guide Lines" for assessing the performance of "Thin Surfacing" are still under development.
  But it might be nice to offer the current "Guide Lines" document as a download in .pdf format so that engineers and technicians might better understand the information contained in each "product" certificate
• Included in each HAPAS certificate is a disclaimer with words to the effect that the British Board of Agrement (BBA) is not responsible for any failure of the "product" or any other claim related to the "product" failure.
  So it follows any premature failure, short life span, of a Thin Surfacing will have the same consequences as the failure of a generic mixture, i.e. it will be the responsibility of the main contractor, who will seek redress from his supplier, or the specifying organisation.

What I am trying to bring home to the purchasers of these mixtures is that you still need a good Materials Engineer / Road Pavement Engineer to assist in choosing the Thin Surfacing that is most suitable for the site conditions where you are going to use it. There are Thin Surfacings available that are excellent products and when correctly selected for particular site conditions will perform very well, but just any thin surfacing will not meet the demands of every site. 
However, do not choose, a branded, more expensive bituminous mixture, until you have ruled out less costly, but well proven generic products that are specified in BS 4987 and BS 594.
HAPAS certified products are just not necessary in most local authority situations.
But on motorways and trunk roads in England it is a requirement that Thin Surfacings with a HAPAS certificate are used as the surface course.

So, it is likely that all the letters that were included in that well known engineering journal were correct because Thin Surfacing is such a diverse subject.
But please, do not believe the sales pitch and the glossy brochures, not if you call yourself an engineer/engineering technician. 
In any organisation I believe it is the responsibility of someone to ascertain the engineering properties of the actual material you will be receiving, before using it, and if you do not know the right questions to ask, and you would not understand the answers if they were supplied, you had better go looking for a good Materials Engineer, if you can find one.

Learning about Bituminous Mixture Design and Properties
If you wish to gain some understanding of bituminous mix design and the properties associated with particular designs I can recommend a visit to the outstanding website of the Turner - Fairbank, Highway Research Center, with its considerable library of freely available material.
In particular the section on Asphalt Pavement Technology, it is an excellent source of information on the subject of mix design. I know of no UK based website that offers the depth of information on bituminous mixtures that this site does, much of it able to be downloaded in .pdf format.
If you are starting out on a bituminous mixture learning curve I would suggest the "Superpave Mixture Design Guide". I will leave you to find the link to this document so that you may explore other aspects of the site and perhaps research why the "Superpave" programme was set up 
in the first place.
You will find other links to excellent websites offering guidance and knowledge relating to bituminous mixtures on the page on this website,
LINKS TO SOURCES OF INFORMATION ON OFFICIAL AND SEMI-OFFICIAL WEBSITES

Assessing Road Surface Skid Resistance
I will keep this item brief as all I wish to do is direct you to a report on the website of the Highways Agency, the Corporate Documents section.
This report relates to an incident that may have involved a road surface with low resistance to skidding, but which was found not to be the case. However the the implications of the incident are not relevant the bulk of the report, and this is what I wish to bring to your attention.
This report although of nine pages is an excellent concise, yes concise, but comprehensive document on the entire subject of road surface friction/skid resistance.
I thoroughly recommend its reading to all of you involved in highways maintenance who wish to gain initial knowledge on this subject, which you can then pursue in greater depth by exploring the pages of this website that give guidance on skid resistance.

Motto of the Month

"One should take good care not to grow too wise for so great a pleasure of life as laughter."