IMPORTANT UPDATE
Major changes have been introduced (from 1st. January 2008) relating to the way in which  bituminous mixtures are specified, both Hot Rolled Asphalts and Bitumen Macadams.
Rather than repeat myself on the process and nature of these changes may I suggest you study the Summer 2007 Newsletter to get up to date.
However do not throw away your BS 594's and your BS 4987's for a while, if ever, as they contain information on good designs and working practice, you will need them to convert your current "well tried" mixtures to an equivalent new BS EN specification using the new standard,

BS EN 13108-4 : 2006 : Bituminous mixtures - Material Specifications - Part 4 : Hot Rolled Asphalt.

Read on for information on BS 594 and its past development :-

Please do not be too discouraged by the amount of changes that have occurred in BS 594 over recent years, they are in fact relatively minor in relation to the overall content of the specification. 
This remains an excellent document for providing information and guidance on the specifying, transporting, laying and compaction of hot rolled asphalt. 
I still believe using the information provided in the standards BS 594 and BS 4987 ( bitumen coated macadams ) is a good basis for the future specifying of the requirements of bituminous mixtures for road construction and maintenance.
It is my opinion that "converting" existing generic designs for commonly used bituminous mixtures to the new form of BS EN  13108 family of specifications is the best and most economical method to adopt, especially for local highway networks.
But you, yes you, must be the one to know which is the best bituminous bound material for your site, you should not, and must not, rely on the contractor or supplier to do your job for you. 
Their choice could be influenced by factors other than the most cost effective option to the customer, i.e. you, and whoever you represent, most probably the general public. 
If you need guidance talk to your Materials or Road Pavement Engineer.
From what I have seen the new form of specifying bituminous mixtures will not be as dire as predicted, they are a mixture of good news and bad news.
( I particularly appreciate the publication of the standard for stone mastic asphalt, which now allows you to specify the type of SMA you want, although I personally still believe that no SMA's should be porous. )
Do not panic, as I feel that if you know the nature of the bituminous mixture you require you will be able to specify it from an "official" British (European) Standard, which I regard as good practice.
The danger may come, for local authority Engineers and Engineering Technicians, with the introduction of very large "Alliances" of local authorities to create "Framework" deals with large contractors and suppliers.
These "Alliances" will include the Highways Agency as a major, possibly controlling partner, and the Highways Agency may wish to introduce the practice of only permitting proprietary (branded) bituminous mixtures for surface course layers, as is currently the situation with motorways and trunk roads.

I personally believe the loss, or dilution, of such an excellent pair of understandable, specifications for Hot Rolled Asphalt in the UK is an error of judgment, a decision probably not made by practicing highway engineers, but by ill advising "advisers".
The distinct bituminous mixture that is hot rolled asphalt tends to be "special" to the UK and has provided many decades of safe, durable and cost effective road surfacing, as well as being entirely recyclable into "new" bituminous mixtures when the end of its ability to provide the necessary surface characteristics arrives.
Its dense, high bitumen content nature having kept the matrix of the material remarkably well preserved

I will repeat myself here to stress that now this (BS 594) specification is superseded the proven generic designs it contains can be replicated by the appropriate use of the new means of specification for bituminous mixtures., "a rose by any other name will smell as sweet".

However past updates/changes to BS 594 do need to be understood as they will be reflected when using the new forms of specification, and there have been some significant changes in the recent past that need noting, and that are included in the new BS EN 13108 : Part 4. 

The latest version of BS 594:Part 1 is,
BS 594 : 2005 : Hot rolled asphalt for roads and other paved areas : 
Part 1 : Specification for constituent materials and asphalt mixes
The only significant difference to the previous edition (2004) appears to be a request for producers to record retained amounts on extra sieves such as 4mm. and 1mm. when analysing samples, this being done with Factory Production Control (FPC) in mind in the future.
As I understand it, with FPC could come different "specifications" for HRA's manufactured at different production plants.

The newly introduced specification follows on the heels of the previous standard introduced on the 1st. of January 2004.
BS 594, Parts 1 & 2 were previously updated in August 2003 to include changes brought in due to the introduction of BS EN 13043 : 2002 : Aggregates for bituminous mixtures and surface treatments for roads, airfields and other trafficked areas
which will introduce a number of changes relating to the size designations of aggregate, the material description and associated test methods to determine aggregate and mixture performance.

I am still including reference to previous (recent) changes in BS 594 for background information, but this is not required learning for the user of the standard, just of interest to the more knowledgeable reader.

The information in the tables below will still be very useful as a GUIDE but only as a GUIDE, refer to the current British Standard for up to date information.

NOTE, the more significant changes occurred in 2002 edition.

BS 594 : 2002 : Hot rolled asphalt for roads and other paved areas: 
Part 1 : Specification for constituent materials and asphalt mixes. 
Part 2 : Specification for the transport, laying and compaction of rolled asphalt. 

# bitumen grade reference are now in accordance with, 
BS EN 12591 : 2000 : Bitumen and bituminous binders - Specification for paving grade bitumens 
# the terms surface course (wearing course), binder course (basecourse) and base (roadbase) are now used to describe pavement layers
Note - I have not yet changed the material descriptions in the table below !
# now includes specification requirements for testing surface course mixtures relating to deformation resistance
# there is reference to in plant blending of bitumens to create further viscosity grades of binder
# the design type R surface course mixtures have been deleted
# introduction of bond coats with reference to BBA/HAPAS approval
# tack coats and bond coats are now specified according to the binder percentage of the upper layer and the rate of bitumen actually deposited on the surface rather than the rate of spread of bitumen emulsion

There are other changes which may be significant in certain circumstances so you need the most recent standards, and probably a good Materials Engineer to point them out to you.

One of the principle differences you will find in the amended specifications is the of viscosity of binder grades, this can be briefly described as,
the 50pen. binder option remaining, 
but 100pen. has been replaced by 125pen, 
and 70pen. has been replaced by an 85pen. binder, that is if your bituminous material producer actually carries 85pen. as a stock item. 
If an 85pen. binder is unavailable it means the difference in binder stiffness between 50pen. and the next binder option, i.e. 125pen. has increased and careful thought will be needed with regard to the grade of bitumen used. 
Do you select a stiffer 50pen. binder or a less stiff 125pen., now that the 100pen binder option has been removed and the 85pen binder is not available.
Which ever binder you choose with regard to its engineering properties, it may require some changes in working practice as a result of the change.

A great deal of information is presented here on the many hot rolled asphalts that are specified in,
BS  594 : Part 1
If you are in any way responsible for ordering / purchasing / supervising the laying of hot rolled asphalts you,
MUST have access to both Parts 1 and 2, of BS 594 of the appropriate edition quoted in the contract.
The information contained in them is excellent, and if you follow their guidance you will not go far wrong, but it would be even better if you could also consult with your Materials Engineer / Technician, if your organisation still has such a person.

With the more recent editions of the standard there is an ever increasing amount of "small print", I am afraid this needs studying closely to avoid NOT being supplied with the nature of bituminous mixture that you thought you had specified.

A look at the main use off hot rolled asphalt as a durable surface course employing the economic use of high specification aggregate as a precoated chipping can be viewed by pressing -----------------------------------------> HERE

SUMMARY OF RECENT CHANGES, to specifying Hot Rolled Asphalt (from 1st. January 2008)

A great deal of information is presented below on the many hot rolled asphalt mixturs that were specified in BS 594.
If you wish to use the bituminous mixtures described below in the future, after 1st. January 2008, you will need to convert them to an equivalent bituminous mixture using,
BS EN 13108-4 : 2006 - Bituminous mixtures - Material specifications - Part 4 : Hot Rolled Asphalt 
If you were in any way responsible for ordering / purchasing or supervising the laying of hot rolled asphalt you should have had access to both Parts 1 and 2, of BS 594 of the appropriate edition quoted in the contract.
The information contained in them is excellent, and if you follow their guidance to specify "equivalent"  bituminous mixtures you will not go far wrong, but it would be even better if you could also consult with your Materials Engineer / Technician, if your organisation still has such a person.

Guidance on the transformation of specifying from BS 4987 and BS 594 to BS EN 13108 can be found in, 
PD 6691 : 2007 : Guidance on the use of BS EN 13108 Bituminous mixtures - Materials Specifications

It is also necessary to be aware that the "Part 2's" of both BS 4987 and BS 594 have been combined in to the document, 
BS 594987 : 2007 : Asphalt for roads and other paved areas - Specification for transport, laying and compaction and type testing protocols.

If you are actively involved in the specifying, ordering or use of Bituminous Mixtures you do need to have access to the above new documents.

BE FULLY AWARE ! ! ! ! !
THE INFORMATION BELOW HAS BEEN SUPERSEDED IT REMAINS FOR GUIDANCE PURPOSES ONLY