temporary road markings: working group findings · road marking paint is a good option in the right...
TRANSCRIPT
TEMPORARY ROAD MARKINGS:
WORKING GROUP FINDINGS
April 2003
CONTENTS
1 Introduction 1
2 Temporary Traffic ManagementDesign and Specification 1
2.1 Road Marking and masking 1
2.1.1 Options 1
2.2 Road Marking and masking 1
2.2.1 Hot Applied Thermoplastic Road Markings 1
2.2.2 Temporary Road Marking Tape 2
2.2.3 Temporary Reflecting Road Studs 2
2.2.4 Road marking paint 2
2.3 Masking 5
2.3.1 Hot applied Thermoplastic Road Markings 5
2.3.2 Temporary Road Marking tape 5
2.3.3 Road marking paint 5
3 Road Surface Types 6
3.1 Description 6
3.2 Advice on temporary markings for thin surfacings 6
4 Application and Removal 8
4.1 Application and Removal Issues 8
4.1.1 Hot Applied Thermoplastic 8
4.1.2 Temporary Tape 8
4.1.3 Temporary Studs 8
4.1.4 Road Marking Paint 9
4.2 Removal methods 9
4.2.1 Hot Compressed Air (H.C.A.) Lance 9
4.2.2 Mechanical Scabbling 9
4.2.3 Forced Air Abrasive (Shot Blasting) 9
4.2.4 Mechanical/hand chipping 10
4.2.5 New developments 10
5 Regulation and Approval Issues 11
5.1 Approved materials 11
5.1.1 Road markings 11
5.1.2 Road studs 11
5.2 Stud option for standard road markings 11
5.3 Authorisation of markings 11
6 Summary 12
7 References 13
Appendix 1 - Advice on temporary markingsfor thin surfaces – background 14
The members of the Temporary Road Markings Working Group were:
Mr Chris Glen (Chairman) Highways Agency
Mr Nigel Bayley Traffic Management Contractors Association (TMCA)
Mr Graham Coe TRL Ltd.
Mr David Edwards Road Safety Markings Association (RSMA)
Dr Cliff Nicholls TRL Ltd.
Mr Mike Pocklington Reflective Equipment Manufacturers Association (REMA)
Mr Brian Turner Department for Transport
Mr Sydney Xavier Highways Agency
1
1 Introduction
At major road works, road markings often need to be removed or masked and temporary markingsprovided. Temporary markings associated with the provision of speed cameras can also be required atroad works. The ease and success of the application, removal and the durability of temporary roadmarkings has always been subject to the nature of the road surface and the weather conditions.However, recent developments in surfacing materials have added another level of complexity to theseprocesses. The new EU Standard on marking materials has also complicated the specification ofproducts.
In response to these concerns, a working group was convened comprising representatives from theHighways Agency, Department for Transport, Traffic Management Contractors Association (TMCA),Road Safety Markings Association (RSMA), Reflective Equipment Manufacturers Association (REMA)and TRL Ltd. to investigate current issues relating to temporary road markings.
This document deals with the findings of the Working Group and is intended to provide guidance fordesigners in their choice and specification of temporary road markings, and for practitioners on issuesrelating to the application, maintenance and removal of temporary road markings at road works.
2
2 Temporary Traffic ManagementDesign and Specification
2.1 Road Marking and masking
2.1.1 Options
In choosing the form of temporary markings, account must be taken of the circumstances specific tothe project.
Use of each category of temporary marking material is constrained by factors such as weather,temperature and, in particular, the nature of the road surface to which the marking is to be applied.Section 3 discusses road surface types. The specification for each temporary marking material is dealtwith in Section 5.
Wherever practical, for the sake of consistency, the category of temporary marking material/productshould be continuous in each direction throughout the traffic management layout.
The removal of conflicting road markings can raise issues that need consideration before a product isspecified as a preferred option. An example might be the type of road surface to be encountered andwhether it may be damaged by a particular removal process. Section 3 deals with road surface typesand Section 4.2 deals with the removal of road markings.
The categories of temporary marking material are given in Sections 2.2.1 to 2.2.4 and in Table 1.Masking is dealt with in Section 2.3.1 to 2.3.3 and Table 2.
2.2 Road markings
2.2.1 Hot Applied Thermoplastic Road Markings
Hot applied thermoplastic road markings perform well in terms of durability, conspicuity, speed ofapplication, cost to apply, and skid resistance. This form of marking is used throughout the networkas a permanent marking.
However, the removal of thermoplastic markings is slow and can leave a ghosting of the marking andscarring of the surface. If the surface is to be replaced, and there will be no need to remove thetemporary marking, then this is not an issue and hot applied thermoplastic should be the preferredoption. On new carriageway surfaces, residues are generally unacceptable. The likelihood of residueson negative texture surfaces is higher than on Hot Rolled Asphalt (HRA) because of the tendency forthe hot thermoplastic material to run into the voids within the surfacing layer.
2.2.2 Temporary Road Marking Tape
Temporary road marking tape is durable for up to 3 months subject to satisfactory application andoffers good conspicuity and skid resistance, though it is comparatively expensive and is slow to applybecause of the surface preparation required. White temporary road tapes are available in a variety ofwidths including 100mm, 150mm and 200mm.
3
The chief disadvantage of tape is that it will not adhere to the carriageway surface in wet and/or coldconditions. There are particular difficulties with negative texture surfaces; in the wet, the pumpingaction of the water can cause the tape to lift from the surface even when correctly applied in dryconditions. Temporary tape can be very hard to remove if it is constantly overrun (see Section 4.1.2).
2.2.3 Temporary Reflecting Road Studs
Temporary reflecting fluorescent green/ yellow road studs may be authorised as an alternative tomarkings for temporary delineation at road works (see Section 5.2 and Chapter 8 of the Traffic SignsManual, paragraph 3.3.10). These studs are usually approximately 100x50mm (4"x2") and are madefrom fluorescent green/ yellow high impact polystyrene, with self-adhesive vinyl reflectors. They areespecially noticeable in wet night-time conditions when their reflective system gives good guidance.The raised profile of the stud also acts as an audible warning to drivers if over-run.
Temporary road studs are designed to be trafficked but not constantly or heavily over-run, and higherbreakages than normal can occur if scheme designs indicate such use.
These studs can be fixed to the road either with a bituminous hot-melt adhesive (hot-melt) or by wayof a sticky butyl/bitumen pad pre-fixed to the stud (self-adhesive).
Hot-melt studs stick well to road surfaces but leave a clear mark on the carriageway after removal, soare less appropriate for new surfaces. They adhere well on dry negative texture surfaces but onceagain, when removed, they leave a mark on the road surface. The road surface can also be damagedwhen they are removed.
Self-adhesive studs are fast to lay and remove, and leave minimal traces, but are prone to becomingdislodged, particularly if they are used in place of lane lines. On negative texture surfaces in the wet,there can be problems with the self adhesive studs becoming dislodged because of the pumpingaction of the water, though the application of a glue prior to installation can help (see Section 4.1.3).This is less of a problem with hot-melt studs.
An issue with temporary road studs is their tendency to ‘sink’ into the surface if constantly over-run,particularly on thin surfaces with higher binder content (see Section 3). This can be minimised by theuse of studs with a large (approximately 100x100mm, 4" x 4") footprint. Hot-melt studs seem to sinkless than self adhesive, possibly because the hot-melt bitumen fills in the voids in open texturematerials.
Temporary studs cannot be masked and therefore must be removed when they are no longerrequired.
2.2.4 Road marking paint
Paint is generally applied through an airless spray machine, and can be applied at walking pace. As aroad marking, with glass reflective beads applied to the surface, it is very effective, with luminanceand retroreflectivity comparable with temporary tape. It is also much cheaper than tape or hot appliedthermoplastic. However, because of its thinness, paint is less visible than thermoplastic in the wet. Itis less durable than hot applied thermoplastic, but this may be less of a concern for temporaryapplications.
Road marking paint is a good option in the right conditions (see Section 4.1.4), in terms of both costand performance on an old carriageway where the road surface is to be replaced and there will be noneed to remove the marking. The skid resistance of paint can be improved by the application of anti-skid material while it is still wet. When used on new carriageways or carriageways that will not bereplaced, paint is almost impossible to remove.
4
Tab
le 1
:R
oad
Mar
kin
g O
pti
on
s
Key:
****
*Hi
gh/G
ood
****
Abov
e av
erag
e**
*Av
erag
e**
Belo
w a
vera
ge*
Low
/Poo
rN
ote
1Th
ixot
ropi
c gl
ue m
ixed
can
be
used
with
a m
anuf
actu
rers
prim
er to
aid
adh
esio
n, b
ut it
can
be
very
diff
icul
t to
rem
ove.
Not
e 2
Can
be d
iffic
ult t
o re
mov
e if
cons
tant
ly o
ver-r
un fo
r lon
g pe
riods
. See
Sec
tion
2.2.
2.N
ote
3Th
ixot
ropi
c gl
ue a
pplie
d p
rior t
o fix
ing
the
self
adhe
sive
stu
d.
Perf
orm
ance
as a
mar
king
****
****
*
****
*
****
*
****
Suit
abili
tyfo
r co
nsta
ntov
erru
nnin
g
****
*
***
Not
e 2
** ***
*
Rem
oval
Wit
hout
Scar
ring
* ****
*
****
*
* *
Tem
pera
ture
Inde
pend
ent
****
*
* ***
****
*
*
Wea
ther
Inde
pend
ent
****
* ***
****
*
Adh
esio
nto
thi
nsu
rfac
e
Usi
ngPr
imer
N/A
****
*N
ote
1
****
*N
ote
3
N/A
N/A
Prod
uct
Ther
mop
last
ic
Tem
pora
ry ta
pe
Tem
pora
ry s
tud
– se
lf ad
hesi
ve
Tem
pora
ry s
tud
– ho
t-m
elt
Pain
t
Adh
esio
nto
new
HRA
surf
ace
****
*
***
****
*
****
*
****
*
Adh
esio
nto
old
HRA
surf
ace
****
*
** ***
****
*
****
*
Adh
esio
nto
thi
nsu
rfac
e
No
prim
er
****
*
* ** ****
*
****
*
Spee
d of
App
licat
ion
****
** ****
****
****
Spee
d of
Rem
oval
** ***
****
*
****
*
*
5
2.3 Masking
2.3.1 Hot applied Thermoplastic Road Markings
Black thermoplastic material can be effective in masking existing thermoplastic markings. However, inwet conditions the black material can reflect light and appear as a road marking and it is thereforeadvisable to apply black grit when laying the black material to give a matt finish to its surface. Whenadditional thermoplastic or paint is used for covering or reinstating existing markings, care must betaken to ensure that the total thickness of the marking does not exceed 6mm.
It is practically impossible to completely re-expose the white thermoplastic marking once it has beenoverlaid by black thermoplastic. Although it is not always necessary to remove black thermoplastic ifthe marking is under 6mm, the use of black thermoplastic should only be a temporary measurebecause wear of the black material will eventually leave the white marking showing through.
2.3.2 Temporary Road Marking tape
When used for masking, the majority of the adhesive area is thermoplastic to which the temporarytape adheres relatively well. The black tape should be 50mm wider than the marking that it iscovering. When removed, the tape generally leaves the road surface and the permanent marking ingood condition.
2.3.3 Road marking paint
As a masking material, paint can be effective for masking either paint or thermoplastic markings andis fast to apply and is inexpensive, although a black grit must be surface applied to give the requiredanti-skid characteristic and a matt finish. It is particularly effective masking painted white lines.However, like thermoplastic, application of black paint for masking purposes is a short term solutiononly because the black paint will wear eventually to reveal white markings underneath.
Table 2: Road Marking Masking Material Options
Key:
***** High/Good**** Above average*** Average** Below average* Low/PoorNote 1 The solvent based primer softens the surface of thermoplastic markings and can leave a black film on the
marking surface.Note 2 Constant overrunning can also lead to removal problems. See Section 4.2.Note 3 The adhesion to existing road markings is reliant on the existing markings being of good quality prior to the
masking application.
Adhesionto existingmarking(Note 3)
***
*****
*****
Suitabilityfor constantoverrunning(Note 2)
****
***
*
MaskingPerformance
****
****
**
Re-exposureof originalmarking
****Note 1
N/A
N/A
TemperatureIndependent
*
*****
*
WeatherIndependent
*
****
*
Product
Temporarytape
Thermoplastic
Paint
Speed ofApplication
**
***
***
6
3 Road Surface Types
3.1 Description
In the last decade, thin surfacing systems, which are a diverse set of proprietary asphalt materials,have become the predominant surfacing option. For use on trunk and most county roads, a thinsurfacing system must have a Roads and Bridges certificate under the Highway Authorities ProductApproval Scheme (HAPAS) from the British Board of Agrément (BBA)1. For the purpose of this scheme,a thin surfacing system is defined as a proprietary bituminous product with suitable properties toprovide a surface course that is laid at a nominal depth of less than 40 mm (BBA(2000)). An exampleof a document that gives further information on thin surfacings is Nicholls (2002).
Because the definition of thin surfacings is relatively wide, it is impossible to identify definitiveproperties for these systems. However, those currently on the market are designed with thepreference for low-noise surfacings and have relatively open surfaces. As such, there are markeddifferences from the surfacings previously used for major roads which, in general, were of hot rolledasphalt with pre-coated chippings.
3.2 Advice on temporary markings for thin surfacings
When selecting the type of temporary marking to use on a particular scheme with newly laid asphalt,the properties of the asphalt layer should be taken in consideration. The acceptable options, based ona limited survey reported in Appendix A, are given in Table 3, but other factors, such as the type ofsite, may also have a significant effect but were not observed because of the similarity within the datareviewed.
The method for removing such markings should be considered before application is started.
1 BBA-HAPAS certificates
BBA-HAPAS certificates can be downloaded from the relevant page in the BBA site on the web,www.bbacerts.co.uk/
The relevant page can be found by searching either for the name of the product or supplier or for “thinsurfacing” to get a current list of the pages for all relevant certificates.
7
Table 3: Acceptable options for temporary markings on newly laidsurfacings
* Definitions:
Unmodified binder: Paving grade bitumen in accordance with BS EN 12591: 2000 (Bitumen andbituminous binders - Specification for paving grade bitumens)
Modified binder: Polymer-modified bitumen
** Based on small 100mm x 50mm (4" x 2") studs in use at the time of writing.
TemporaryTape
SuitablePossible
Unsuitable
SuitablePossible
Unsuitable
SuitablePossible
Unsuitable
SuitablePossible
Unsuitable
SuitablePossible
Unsuitable
SuitablePossible
Unsuitable
SuitablePossible
Unsuitable
SuitablePossible
Unsuitable
TemporaryStuds**
SuitableSuitableSuitable
SuitableSuitableSuitable
SuitableSuitableSuitable
SuitableSuitableSuitable
PossiblePossiblePossible
PossiblePossiblePossible
PossiblePossiblePossible
PossiblePossiblePossible
Binder type*
Unmodified
Modified
Unmodified
Modified
Unmodified
Modified
Unmodified
Modified
Layerthickness
< 35 mm
35 - 40 mm
Max. nom.agg. size
14 mm
10 mm
14 mm
10 mm
Bindercontent
> 6.0 %6.0 %
< 6.0 %
> 4.9 %4.9 %
< 4.9 %
> 5.4 %5.4 %
< 5.4 %
> 3.5 %3.5 %
< 3.5 %
> 6.0 %6.0 %
< 6.0 %
> 4.9 %4.9 %
< 4.9 %
> 5.4 %5.4 %
< 5.4 %
> 3.5 %3.5 %
< 3.5 %
8
4 Application and Removal
4.1 Application and Removal Issues
This section deals with the issues relating to the application and removal of temporary road markingmaterials. Section 4.2 gives more information on the methods available for removing the markingsand a summary of removal methods is given in Table 4.
4.1.1 Hot Applied Thermoplastic
Hot applied thermoplastic adheres to the surface and, once applied, the bond cannot be penetratedby moisture. However, this bond cannot be created in the presence of moisture and debris and,therefore, the surface must be dried and cleaned prior to application. Nevertheless, thermoplastic canbe applied in low temperatures and to all surfaces. It can be applied in a wider range of weather andtemperature conditions compared with self adhesive studs and temporary tape.
Thermoplastic can be applied more thinly than in the permanent situation and this can lead tobenefits in terms of quicker removal and possible less damage to the road surface.
4.1.2 Temporary Tape
Temporary tape adheres to the road surface by a waterproof seal with the carriageway. If this seal ispenetrated by water, the adhesion fails. For good adhesion, the road surface must be dry, clean, freefrom salt, and the ambient temperature needs to be above 4oC. The surface is sprayed with a solvent-based primer which must then be left to dry. Tape is then applied onto the dry primer. Temporary tapedoes not perform well on open textured or rugous surfaces in wet conditions when water can flowthrough the surface and a pumping action causes the tape to lift.
At low temperatures, tape is less flexible and is less able to take the shape of the contours of thesurface. The solvent based primers will not cure at low temperatures and cannot be applied in wetconditions.
There are situations when temporary tape can be removed easily and quickly from the road surfacewithout leaving permanent residues, for example, when it is used as an edge line. However, if it hasbeen constantly overrun for long periods, the polymer matrix can break up such that it can only beremoved in small pieces. Under no circumstances should heat be employed to removetemporary tape as toxic fumes are given off.
4.1.3 Temporary Studs
Hot-melt temporary studs can be applied in all conditions, though this is dependent on the surfacehaving been dried. Problems with adhesion can occur when steam pockets are created by the hotbitumen coming into contact with moisture that is resident in the voids of open textured surfaces.
Self adhesive temporary studs can be applied in most conditions, but the bitumen pad adheres lesswell at low temperatures. Drying of the surface prior to application is required. The stud adheres tothe surface by the bitumen pad creating a waterproof seal with the surface. If this seal is penetratedby water the bond fails. Temporary self adhesive studs do not perform well on open textured orrugous surfaces. The application of a thixotropic glue prior to the installation of the self adhesive studcreates a waterproof seal between the bitumen pad and the surface and improves adhesion. This isparticularly useful on thin surfaces.
Temporary studs can be removed from the road surface by sliding a shovel or “chipping bar” underthe base of the stud. The most effective method of removal is by using a skid steer loader or tractorfitted with a bucket.
9
4.1.4 Road Marking Paint
Paint adheres to the surface by a chemical bond and its curing time is adversely affected by lowambient air temperatures, moisture and debris. The curing time prohibits its use during rain. Blackpaint requires a surface application of anti-skid material to aid abrasion and lessen highlight glare.White paint requires the application of glass beads to provide retroreflectivity.
Because paint is absorbed into the binder of the road, only the surface layer can be removed withoutdamage to the surface. Masking with black paint is the only effective method. However, paint can beremoved successfully from concrete carriageways because it is not absorbed.
4.2 Removal methods
Unless traffic is to be confined to a single lane delineated by closely spaced cones on each side (seeChapter 8, paragraph 3.1.3), where existing road markings conflict with temporary trafficmanagement arrangements they must be removed or masked to avoid confusion in the interest ofsafety. Masking of the markings can be undertaken using temporary tape, thermoplastic or paint (seeSection 2.3). The removal of road markings provides a permanent solution and avoids the possiblefailure of masking materials and consequent exposure of conflicting markings.
The main removal methods are as follows:
4.2.1 Hot Compressed Air (H.C.A.) Lance
This equipment works by using hot compressed air to vaporise the road marking. Because of thenature of the equipment used, it is regarded as a mechanical method of removal. The temperaturesinvolved are likely to cause damage to the road surface and, for this reason, the equipment isinappropriate for use on thin surfaces. Noise, smoke and fumes are also important issues that needconsideration. The H.C.A. lance operates at a relatively high noise level (120 dB(A)) and itsappropriateness close to other site operations and urban areas must therefore be assessed. Thevaporised thermoplastic can cause clouds of smoke which will affect drivers’ visibility and, althoughnot toxic, may be a health and safety issue.
4.2.2 Mechanical Scabbling
Mechanical scabbling grinds the marking from the surface, but total removal is not possible withoutdamaging the surface. Small amounts of marking are left in the voids of the surface and this residuehas to be masked or removed by other methods. The main use of mechanical scabbling is forremoving the bulk of markings and the removal of raised ribline markings which are exceptionallythick. This method produces large amounts of debris that must be cleaned up quickly to avoid thethermoplastic particles re-adhering to the surface. The equipment is also relatively noisy and operatesat 90 dB(A), but can peak to 104 dB(A).
4.2.3 Forced Air Abrasive (Shot Blasting)
Abrasive particles are projected by high pressure air at the road marking. The particles abrade theroad marking from the road surface. This method leaves very little scarring because heat is notgenerated during the process but some polishing of the aggregate is likely. Total removal of roadmarkings from porous/thin layer surfaces can only be undertaken with this process. The equipment isrelatively noisy and operates at 105 dB(A). If this method is specified, the time factor must beconsidered because removal of road markings by shot blasting is very slow.
Consideration must be given to the environmental effects of the discarded abrasive material usedduring the removal process, especially in water courses. Captive shot blasting can be considered butthe binder that is recycled with the abrasive material tends to clog the machinery.
10
4.2.4 Mechanical/hand chipping
This method is only suitable for removing temporary studs and tape.
4.2.5 New developments
New methods of removing markings are being developed. One that is commercially available is amethod of forced air particle removal that employs dry ice as an abrasive particle. The dry icevaporises during the removal process leaving very little debris. Another new system uses a heatedmixture of sand and water applied at low pressure to remove markings. The developer claims that theremoval process yields a relatively small amount of damp residue that can be swept up for laterdisposal.
Table 4: Options for the Removal of Road Markings
Key:
***** High/Good
**** Above average
*** Average
** Below average
* Low/Poor
Note A Removal of markings by mechanical scabbling can only be done to the point of damage ofthe surface. Total removal is not possible without some surface damage.
Note B Paint does not have any “bulk” to it so removal by mechanical scabbling cannot be undertaken.
Note C Polishing of the road surface occurs.
TemporaryTape
N/A
N/A
N/A
**
***
Studs:Hot-melt, SelfAdhesive
N/A
N/A
N/A
**
****
Paint
*
*Note B
*
N/A
N/A
Thermoplastic
***
*****Note A
*
*
N/A
LowNoise/Fumes
*
***
**
*****
****
ThinSurface
*
***Note A
****Note C
*****
****
Method
Hot compressedair (HCA) lance
Mechanicalscabbling
Forced airabrasive
Hand“chipping”/picking
Mechanicalchipping
HRASurface
***
****Note A
****Note C
*****
****
Speed of removal of:Minimising damage to:
11
5 Regulation and Approval Issues
5.1 Approved materials
5.1.1 Road markings
All road marking materials are subject to European Standards BS EN 1436; BS EN 1790 for preformedmaterials (e.g. tapes) and BS EN 1824 for road trials for materials from both standards. The physicalproperties of road marking materials are covered by BS EN 1871.
Approved materials are issued with a road trial test report to the appropriate standards by the testingorganisation, like British Standards Institution (BSI), indicating which classes from the standard thematerial has achieved. The Manual of Contract Documents - Specification for Highway Works, Series1200, has stipulated the minimum classes which will be required of any marking to be used on atrunk road.
Black masking materials, including temporary tape, thermoplastic and paint, are not included in theEuropean Standards, but are covered by British Standard BS 7962.
It is essential that wear of the masking material should not expose the original white materialbelow it.
5.1.2 Road studs
Road studs are subject to European Standards BS EN 1463 Parts 1 and 2. The Traffic Signs Regulationsand General Directions 2002, including The Traffic Signs (Amendment) General Directions 2003,prescribe the minimum classes from those standards that must be achieved during trials of the studsto be used on the public highway. It would be unlawful to use a stud on the highway that was notcertified to those minimum classes.
5.2 Stud option for standard road markingsChapter 8 of the Traffic Signs Manual provides for the use of road studs at two metre spacing in placeof lane markings in detail J2. Seven studs at one metre centres have been found to provide a betterrepresentation of the six metre marking being replaced and to retain a clearer appearance of amarking should any of the studs become dislodged. It is therefore recommended that one metre studspacing should be used in situations where detail J2 is required.
5.3 Authorisation of markingsOnly traffic signs, including road markings, which are prescribed in the Traffic Signs Regulations andGeneral Directions or which have received special signs authorisation may be legally deployed on thepublic highway or other highway to which the public has access.
It is possible, in certain circumstances, to authorise the use of additional signs or markings byapplication in writing to the Department for Transport for England, and the appropriate organisationin Scotland, Wales and Northern Ireland. All applications are judged on their specific merits.
12
6 Summary
This report provides guidance for:
(a) designers in their choice and specification of temporary road markings, and
(b) practitioners on issues relating to the application, maintenance and removal oftemporary road markings at road works.
The relative advantages and disadvantages of the three marking materials currently in use, and thetemporary road stud alternative to markings, including their removal, are described and summarisedin the form of tables. The type of road surface to which the marking is to be applied is important and,in particular, advice is included for temporary markings for thin surfacings.
Removing road markings presents particular problems, some of which are dependant on the type ofroad surface. There are advantages and disadvantages associated with each the methods currentlyavailable and these are summarised in the form of a table.
13
7 References
Advice Note TA 64. Narrow Lane and Tidal Flow Operations at Road Works on Motorways and DualCarriageway Trunk Roads with Full Width Hard Shoulders.(Design Manual for Roads and Bridges 8.4.3). The Stationery Office. (ISBN 0-11-551607-7)
British Board of Agrément (2000). Guidelines document for the assessment and certification of thinsurfacing systems for highways. BBA-HAPAS SG3/98/169, Working Draft 3,British Board of Agrément, Watford.
Department of Transport (1985). The Traffic Signs Manual – Chapter 5 ‘Road Markings’.(ISBN 0-11- 550708-6)
Department of Transport (1991). The Traffic Signs Manual – Chapter 8 ‘Traffic Safety Measures andSigns for Road Works and Temporary Situations’. (ISBN 0-11-550937-2)
Nicholls J C (2002). A history of the recent thin surfacing revolution in the United Kingdom.TRL Report 522. Transport Research Laboratory, Crowthorne. (ISSN 0968-4107)
The Traffic Signs Regulations and General Directions 2002. (SI 2002 No. 3113). (ISBN 0-11-042942-7)
The Traffic Signs (Amendment) General Directions 2003. (SI 2003 No. 393). (ISBN 0-11-044996-7)
British Standards:
BS EN 1436:1998 Road marking materials – Road marking performance for road users
BS EN 1463-1:1998. Road marking materials – Retroreflecting road studs.Part 1. Initial performance requirements
BS EN 1463-2:2000. Road marking materials – Retroreflecting road studs.Part 2. Road test performance specifications
BS EN 1790: 1998. Road marking materials – Preformed road markings
BS EN 1824: 1998. Road marking materials – Road Trials
BS EN 1871: 2000. Road marking materials – Physical properties
BS 7962:2000. Black materials for masking existing road markings – Specification
14
Appendix 1 - Advice on temporary markingsfor thin surfaces – background
Observations on the M6
In recent years, a series of sections of the M6 in Cheshire and Lancashire have been laid with a varietyof thin surfacing systems that have behaved differently in terms of the embedment of temporary roadstuds and the adherence of road marking tape. The systems have been identified and some simplecharacteristics of the mixtures used have been obtained. These characteristics are nominal maximumaggregate size, the nominal layer thickness, the target binder content and whether modified orunmodified binder was used. These characteristics, together with the observed behaviour oftemporary road markings, are given in Table A1.
Models to estimate performance
By comparing the characteristics, it is possible to produce models that estimate the performance of athin surfacing system when temporary road markings are used. The embedment of studs is assumedto depend on the layer thickness (and hence the potential extent of any deformation) whilst theadherence of tapes is assumed to depend on the “stickiness” of the system, as indicated by thebinder content and whether the binder is modified.
Table A1: Properties of thin surfacing systems on M6
* Studs fixed with thixotropic glue;only short lengths of transverse tape used, so adherence would have been moredifficult than with longer lengths of longitudinal tape.
The characteristics of the thin surfacing systems are considered to be the type that can bereadily attainable for any particular location.
Bindercont (%)
6.0
5.0
5.5
6.0
4.9
6.0
5.4
6.0
Tapesadhere
No
Yes
Yes
Yes
No
Yes
No
Yes
Studsembed
No
Yes
Yes
No
No
No
No
No
Thickness(mm)
30
45
35
35
30
35
20
35
Junction
18-19, Holmes Chapel
18-19, central
18-19, Knutsford
23, Haydock
26-27, Gathurst *
28-30, Leyland
34, Lancaster
35, Carnforth
Agg size(mm)
14
14
14
14
14
14
10
14
Bindertype
Unmod
Mod
Mod
Unmod
Unmod
Unmod
Mod
Unmod
15
The data indicate a possible model for the embedment of temporary road studs could be that studs:
● can or will embed if the nominal layer depth is equal to or greater than 35 mm
● will not embed if the nominal layer depth is less than 35 mm
The data indicate that a possible model for the adhesion of road marking tape could be that tape:
● will debond if the adjusted modified binder content is less than 4.9 %
the adjusted unmodified binder content is less than 6.0 %
● can debond if the adjusted modified binder content equals 4.9 %
the adjusted unmodified binder content equals 6.0 %
● will adhere if the adjusted modified binder content is greater than 4.9 %
the adjusted unmodified binder content is greater than 6.0%
where the adjusted binder content is the target binder content times cube root of the ratio of themaximum nominal aggregate size and 14 mm. This ratio is used to compensate for extra bindercontent needed to provide the same binder film thickness on finer aggregate skeletons.
A comparison of the observed and estimated behaviours is given in Table A2, with an overall accuracyof both models of 75 %. The limitations are the range of values where the estimated behaviour isuncertain.
However, the models are only indicative because they are based on relatively few subjectiveobservations. Furthermore, they relate specifically to freshly laid asphalt surfacings, and may not beapplicable to surfacings that have been in service for some time.
Table A2: Comparison of observed and estimated behaviour on M6
6.0
0.75
Tapesadhere
No
Yes
Yes
Yes
No
Yes
No
Yes
Studsembed
No
Yes
Yes
No
No
No
No
No
Tapesadhere
(?)
Yes
Yes
(?)
No
(?)
No
(?)
Studsembed
No
Yes
(?)
(?)
No
(?)
No
(?)
Tapesadhere
0.5
1.0
1.0
0.5
1.0
0.5
1.0
0.5
Studsembed
1.0
1.0
0.5
0.5
1.0
0.5
1.0
0.5
Junction
18-19, Holmes Chapel
18-19, central
18-19, Knutsford
23, Haydock
26-27, Gathurst
28-30, Leyland
34, Lancaster
35, Carnforth
Observed Estimate Accuracy
Total
Average
6.0
0.75