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The Delivery Hub health, safety and environmentRaising the bar 4

Temporary safety barriersVersion 2 - July 2014

An executive agency for the Department for Transport

The delivery hub healTh, safeTy and environmenT - raising The bar 3Temporary safety barriers - version 2 - July 20142

Email: [email protected]

Contents

Scope Page 3

Position Page 3

Risk Assessment Page 4

Surface Condition Page 4

Appendix 1 Page 6

Appendix 2 Page 14

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ObjectiveTo identify good practice in the installation of temporary barrier to protect the work-force and travelling public

BackgroundWith the increase use of temporary barrier guidance was needed on when/ where it should be implemented.

ScopeThis document applies to works delivered for the Highways Agency.

PositionMinimum requirementsFollowing a review of the use of temporary safety barriers (such as varioguard), the need is found to depend upon the individual contract and as a result, a site specific risk assessment should be conducted to assess the need. This will include:

• The speed of public vehicles (recommended on all high speed) • The road layout/sight lines • The duration of the works.

Other factors relevant to the environment of the scheme should also be taken into account.

Where roads are not closed, the temporary barrier decision tool should be used:

For works of less than 28 days the decision tool should be used to conduct a risk assessment. It is recognised that for works of less than two days the deployment of a temporary barrier system is unlikely to be applicable as this will disproportionately extend the duration of the scheme, however an assessment should be undertaken.

If works are greater than 28 days it would be expected that temporary barrier would be used unless a risk assessment showed that this disproportionately increased risk.

A temporary barrier decision tool can be found at http://www.dft.gov.uk/ha/standards/ians/pdfs/ian142.pdf



Risk Assessment

Where temporary barrier and associated works require moving running lanes closer to soft verges a risk assessment should be conducted to address the likelihood of vehicles entering the soft verge.

The risk assessment should consider:• Inspecting the soft verge and produce a plan identifying ‘high risk’ areas.• Implementing temporary verge hardening detail at ‘high risk’ areas.• Central reserve varioguard installations to be pinned at 60m centres.

(as a result of cases where vehicles stray onto soft verge and over correct crossing to central reservation).

• Engage with police to increase visible presence• Enhanced signage and mobile VMS.• Further engagement with freight transport association /road haulage

association to discuss how to reduce risk to road workers.• Installing temporary studs at 1m centres on the edge line where no kerb exists.• Temporary studs to be monitored for damage to identify any potential high risk

areas where vehicles may run off the edge of the carriageway.• Height of temporary barrier when placing temporary signage. • Laying out the barrier and then removing sections for access/egress so these

can be replaced and access/egress points moved as works progress. • The type of terminals (ramps or cushions) , cushions should be considered

good practice and used where available.

Good practice elements to consider are provided in Appendix 1 terminal ends on temporary vehicle restraint systems (TVRS).

Surface Condition

• Assess surface condition as on newly laid surfaces temporary barrier could result in depressions in the newly laid surface.

• Rubber pads can reduce the intensity of the pressure on the surface to avoid rework. Figures 1 and 2 demonstrate this with blue colour representing the most intense pressure.

• Research has shown the standard barrier far exceeds the loading sustainable by the asphalt surface, the addition of the Flexible base significantly reduces this effect to a reasonable level.

• Further detail is provided in Appendix 2 - use of rubber pads on varioguard (temporary restraint).



Workforce Awareness

It is widely quoted that temporary barriers should have a 600mm safety zone, based on N2 testing criteria from BS EN 1317-2:2010.

Workers should be aware that the barrier is likely to move more than 600mm de-pendant on the size of the vehicle, speed of impact and angle of impact.

References

BS EN 1317-2:2010. Road restraint systems performance classes, impact test acceptance criteria and test methods for safety barriers including vehicle parapets http://www.bsigroup.co.uk/

Technical note A1 dishforth to leeming ECI scheme – use of rubber pads on varioguard (temporary restraint).See Appendix 1

DMRB volume 2 section 2 part 8 criteria and guidance for the provision of temporary safety barriers at road works TD 19/06 (2006)http://www.dft.gov.uk/ha/standards/dmrb/vol2/section2/bd2904.pdf

Road restraint systems part 3: performance classes, impact test acceptance criteria and test methods for crash cushions BS EN 1317 -3: (2010)http://www.bsigroup.co.uk

Highways Agency interim advice note 142/11 temporary barrier decision tool (2011)http://www.dft.gov.uk/ha/standards/ghost/ians/pdfs/ian142.pdf

Traffic signs manual chapter 8 traffic safety measures and signs for road works and temporary situations part 1 & 2 (2009)https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/203669/traffic-signs-manual-chapter-08-part-01.pdf

Hierarchy guidance and considerations incorporating lessons learnt for terminal ends on temporary vehicle restraint systems (tvrs) (2014)See Appendix 2

Appendix 1Hierarchy guidance and considerations incorporating lessons learnt for terminal ends on temporary vehicle restraint systems (tvrs)

Appendix 2 Technical note a1 dishforth to leeming eci scheme – use of rubber pads on varioguard (temporary restraint).

http://www.bsigroup.co.uk

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/203669/traffic-signs-manual-chapter-08-part-01.pdf

https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/203669/traffic-signs-manual-chapter-08-part-01.pdf



Appendix 1

Hierarchy guidance and considerations incorporating lessons learnt for terminalEnds on temporary vehicle restraint systems (TVRS)

Part one: First consideration eliminationA) Eliminate end terminal requirement through engineering solution.

B) Eliminate works access / egress points design out requirement for gaps in barrier (TD1906)

Transitions1.1 Engineering Solutions Transitions

Design out riskUse of transitions from permanent to temporary vehicle restraintSystem eliminates the need for p1 ramp taper or crash cushion .Insert 1 example a1 leeming to barton installed april 2014.

1.2 Technical ConsiderationsExisting VRS system must be suitable for connection.Ground conditions must be evaluated.Length of transition may be an issue, accommodating the length ofrequired transition needs to be considered i.e. may vary betweenTCB and OBB

Existing systems that are less than a W4 (working width class) willrequire a modified version of the transition.N2 systems can only be connected to N1 or H1 systems unless adeparture from standard is applied for and granted.

Installation time must be considered for length of works, i.e. if shortterm it might not be practical with risk factors when comparing withinstallation and remove durations. In this case crash cushion shouldbe considered.

Also length of time temporary layout is operational should beconsidered. For example Insert one layout operational for 370 days. Ifshort term crash cushion should be considered.

Consider visibility TD19 8.17/8.18 that must be included in the assessment.

The current criteria RRRAP do not consider Transitions directly andwill require development of a full checklist for implement



Part two: Use of crash cushions on temporary restraint2.1 Crash cushions to be used when traffic passes either side of barrier

A) Roadusers passing either side of Crash cushion.

Example shown insert 2 crash cushion m62 j25 –j30 smartMotorways scheme at j27 / m621.The splitter detail using crash cushion was required as gantry baseWas constructed just east of existing nosing.In splitter areas like this p1 ramps should not be used.

Another example of splitter detail at works access point insert 3.

(B) works traffic passes (works side) and road user (live carriageway side)

In this situation crash cushion should be given high consideration.This would also apply to works exit points this is even more importantas gap can be longer in length.

M1 junction 39 to junction 42 smart motorways - junction 40 entry Slip RoadSection 2 junction 26 to junction 27 E/B looking east (September 2012)



Other benefits of using crash cushion are maintaining works area /haul route width when compared with P1 terminal and flare.

Lessons learnt M62 junction 25- junction 30 in using crash cushions –

By reducing to minimum offset this can give minor damage to crashcushion see insert 4 M62 east junction 29 to junction 30.

Future offsets should follow guidance set in section 2.4 LateralDisplacement zones for crash cushions

2.2 Why use crash cushions

Example of crash cushion M1 junction 39to junction 42 RTC crash cushion hit whendriver fell asleep following long journey from Germany (April 2014).This crash cushion at works access point has possibly saved his life.See Insert five & six

Insert five Insert six



2.3 Technical Considerations Crash Cushions

TD1906“Where the use of crash cushions is proposed by the contractor forSafety reasons, the proposals must be supported by an analysis ofThe benefits* of such deployment which takes into account thePotential risks to both the workforce and the travelling public.”*This document seeks to analyse the benefits

TD1906“7.11 crash cushions should not normally be included in the designsFor temporary traffic management (TTM) designproposals. They may, however, be proposed by the contractor.”

TD1906 is out of date crash cushions should now be considered andIf found to be required used in all TTM design.

TD1906 RRRP will not consider end terminals on TemporaryRestraint

Consider time elements of installation - TD 19 06 “Where eachcrash cushion installation is intended to be in position for less than 28days, the overall benefits to the workforce and road users may beoutweighed by the time/cost of installation, the risks to the installationteam and possible delays to the travelling public. In short durationworks, therefore, crash cushions should not normally be consideredunless there are overriding safety reasons.

Temporary barrier decision tool IAN 142/11“The use of a static crash cushion fitted to a steel plate at the start ofthe working area is a possibility for longer term works. These plateddevices must be installed by suitably qualified personnel inaccordance with approved manufacturer’s instructions in order forthem to provide the maximum protection.

Positioning of the crash cushion must meet the manufacturesSpecification and consideration of maximum practical setback shouldBe considered.

Crash cushions are free standing and do not require connection toexisting VRS systems like P4 terminals. Making crash cushion idealfor site access and egress.

As crash cushions act as attenuators/retarders (like P4 terminal) thevehicle is contained with good impact survival rates (note for impactswithin the tested criteria). Crash cushion testing EN1317-3 considersvehicle impacts up to 1500kg,

The specified approach lengths must be considered, no works shouldbe undertaken in that area – first 32m @ 40mph and 40m withspeeds 50mph and above this should be slow-down / stoppingexclusion distance with no works present. This exclusion zone should be made clear at site induction and regular briefings. If this area is highlight / indicated with equipment i.e. signs or cones maintainingequipment could be a hazard for workforce in such highly trafficked areas.

Location of breaks (gaps) within the temporary vehicle restraintSystem should be minimised and if practical eliminated on bends.

Crash cushions should be considered for contraflow on departure terminals.

TD19/06 8.22There must not be any gaps created in the temporary safety barrierbetween the two opposing flows of traffic in the contraflow.

Gaps cannot be introduced that will permit vehicles to crossover. If emergency access points are included crash cushions should not be considered for end treat-ments, gated systems to be included in the design.



Chevron Markings should be installed on all end terminals both approach and departure. This will help roaduser visually identify terminal end. This control will highlight end terminals during work operations, for example road closures at night hazard to works vehicles reversing.

Avoid coning at location of crash cushion. Use chevron markings this will remove maintenance for roadworker in hazardous area of works.

2.3 technical considerations crash cushions

Crash cushions are listed in the Highways Agency EN1317 Accepted List.For performance criteria you look at the ‘D’ value; this is a zone onboth sides of the cushion that when impacted the cushion may deflectinto. For a head-on impact the cushion will collapse and gain width onboth sides due to the nature of controlled collapse.

Crash cushions cannot have a working width – deflection + barrier asa taped cushion has a variable width.

‘D’ Zones are specified in EN1317-3:2010 in Table 12 copied insert 6;they may have been tested to EN1317-3: 1998 this is accepted by theHighways Agency.

Only D1 and D2 will be practical for traffic management schemes. Inthe case of works access and egress points only D1 should be usedas any further setback can reduce works area / haul route.

For roadwork’s Highways Agency projects should source D1 terminals this will givemore flexibility in minimum setbacks and relocations for different use.

The traffic face of the crash cushion must be the specified ‘D’ value of unitplus 100mm

If the cushion is tapered, the measurement should be made from the widestpoint of the cushion.

Examples:

1) The cushion to be used is a parallel (rectangular) D1 crash cushion (as above).

Minimum setback will be 500mm (D1) + 100mm = 600mm measured from the side face to traffic face of the demarcation line.

2) The cushion is a tapered D2 crash cushion (footprint below) Minimum setback will be 1000mm (D2) + 100mm = 1100mm this to be measured from the widest point (normally the rear).



Part three: Use of P1 ramp terminals3.1 P1 ramps can be safe solution when significant flare can be achieved. Recommend 1.5m minimum (Insert 8) if can be flared further this will reduce risk.

If significant flare can be achieved this will remove risk of vehiclelaunching off ramp. In situations described above a ramp terminal with significant flare could be safer solution than crash cushion.

M1 junction 39- junction 42 smart motorways

M1 junction 39 northbound entry (no injuries) HGV (driver stated he had tyre blow out) then hits TVRS. If the flare had been set back furthersay 1.5m + or had crash cushion this accident could have beenavoided.

The width of works area behind TVRS is around 6 metres.This is adequate width to allow works vehicles through works zoneand also to have increased flare on TVRS.

P1 ramp being hit April 2014



Ramp terminals can be a risk to workforce as well as roaduser whenused at works exit and exit points even at 40mph. See insert 11

Consider crash cushions at works access and egress points.

See specified exclusion zones in Technical data 3.2

The flare on zoneguard was to minimum set back to maintain worksarea. For future schemes crash cushion should be considered if onlyminimum offset flare can be achieved.

A14 Kettering bypass incident at works access point speed limit 40mph.

3.2 technical considerations p1 ramp terminals temporary restraint

TD1906 RRRP will not consider end terminals on temporary restraint

Temporary barrier decision tool IAN 142/11 4.37 slight taper and ramped ends it is normal practice to taper barriers back away from trafficked carriageway by about 1m at the beginning and ramp down end, in accordance with manufactures requirements.

If P1’s are used with limited flare close cloning is required before theP1 and level to gage ramp. Recommendations 7 cones (3.5m)minimum; 10 cones (5m) preferred. This as a visual deterrent only.On P1 terminals that have significant flare and set back with good linemarking demarcations cones should be avoided as a maintenancerisk to roadworker and roaduser.

Chevron markings should be installed on all end terminals bothapproach and departure. This will help roaduser visually identifyterminal end. This control will highlight end terminals during workoperations, for example road closures at night hazard to worksvehicles reversing.



The specified approach lengths must be considered, no works shouldbe undertaken in that area – first 32m at 40mph and 40m at 50mph,and this should be slow It down/stopping exclusion distance with noworks present. This exclusion zone should be made clear at siteinduction and regular briefings. If this area is indicated with equipmenti.e. signs or cones maintaining equipment could be a hazard in suchhighly trafficked areas

Consider TD19 8.17/8.18 with regard to visibility.Crossover potential must also be considered with regard to departure terminals

Visibility and location must be prime concern during the planningphase. Location of breaks within the temporary vehicle restraint systemShould be minimised and if practical avoided on bend.

4.0 Next Steps

1) Continue to monitor terminal ends across all JV projects working within guidance of these documents. TD1906 suggest crash cushions should be monitored -record any damage and near miss incidents to all end terminals.

2) Produce a check list procedure for design stage to consider all the design criteria within available standards and using information and guidance contained within this document. This will show temporary works designer has shown standard of care / due diligence.

When designing for P1 flare TVRS Setback + Flare, so for example if TVRS setback was minimum 375mm and Flare 1500mm = total 1875mm.

Insert 11Setback (As specified by supplier)

Additional P1 Flare



Appendix 2

Use of rubber pads on varioguard (temporary restriant)

OverviewDuring the ECI stage of A1 dishforth to Barton in 2008 the project team workingalong side of asset international (part of the Hill and Smith group) identified the need to install rubber pads on Varioguard prior to installation on newly laid surface course which would cover a length of 22 kilometres of Varioguard was to be laid on new surface course.

Previous Lessons LearntThe last major issue was M25 junction 12-15, with Balfour Beatty, in 2004/ 2005, where the Varioguard was placed on the joint line between ‘rips’ without pads on newly laid surfacing. The total cost of resurfacing at that time was £499k. As a result pads became an option to A1 Dishforth to Leeming project at an additional cost of £72,000 which was included in target cost and accepted by Highways Agency as best practice.

Technical dataThe addition of the asset international varioguard flexible base represents asignificant improvement in barrier sinkage performance on freshly laid asphaltsurfaces. The castellated rubber pad, manufactured in 50º shore hard naturalrubber, maximises efficient rubber usage whilst providing excellent deformationcharacteristics under load.Laboratory based testing was performed at the transport research laboratory (TRL) to map the deformation characteristics of tarmac masterflex asphalt under steady state conditions. The results showed acceptable surface deformation (0.35Mm after 7 days) under controlled temperature conditions of 45ºc when loads of up to 12 tonnes/m2 (117.7 Kpa) were applied.

This figure has been taken as the control for subsequent trials to determine the relative performance of the varioguard flexible base.

Extensive flatness trials were carried out at TRL on a number of varioguard units.The results displayed a generalised trend which suggested that the majority of theBarrier weight is carried by the two ‘end feet’.

These findings were reflected in the physical trials of the flexible base. The barrierWas placed on raised blocks under the two extreme feet to replicate the ‘worst case’Condition of deployment. The assumption was made that the mass of the barrierWould be equally distributed between the two points. A computational pressure matSystem was used to establish the loading conditions of the barrier with and withoutThe asset international varioguard flexible base. The results of this can be seen inFigures 1 and 2.



Although the pressure maps above show an uneven pressure distribution, this datasheet will assume uniformity due to the individual signature of each barrier.Based on the figures presented for the difference in area between the standardbarrier and the Flexible Base, a pressure difference can be calculated.

These figures should be compared to the control for asphalt shear of 117kpa.Standard barrier306.1 Kpa

Varioguard flexible base96.4 Kpa

It can be concluded that whilst the standard barrier far exceeds the loadingsustainable by the asphalt surface, the addition of the Flexible base significantlyreduces this effect to a reasonable level.

Existing surfacingThe A1 D2L project did not install pads on existing A1 carriageway and encountered no damage to carriageway. This is due to the surface being fully cured and ‘workhardened’ through use. The key factors in asphalt deformation are temperature, and curing time. Bitumen, the binder in asphalts, is a visco-elastic material whose strength is very dependant on the temperature. Deformation in the surfacing of roads tends to occur in the few hours each year when temperature is highest. This phenomenon is more acute in the early life of a surfacing when it is cleanest (ie black and absorbs more heat), and the exposed binder has not oxidised, increasing its stiffness. There may be some difference depending on the aggregate size, but this should be minor. As you move further away from the aggregate interlock type of mixture, the more the behaviour of the asphalt can be different. For instance, hot rolled asphalt, or mastic asphalt rely on the mortar for strength, and as a result are far more temperature susceptible (eg the wheel tracking rate at 60 degrees C of SMA will be two or three times that at 45 degrees C, but for HRA it will generally be an order of magnitude greater.)

Lessons learntThe A1 Dishforth to Leeming scheme site team laid permanent lining prior toinstallation of varioguard; the aim being when varioguard was removed lanes couldBe opened without any other operations required.On reflection the project would not have laid permanent lining as the rubber pads

Created indentations in line markings for around 11 kilometres of 2m lines, remedialAction was scabbling damaged line markings within 1mm of surface course and relay at a remedial cost of £11,500. The cause of indentations on line markings could have been partly due to residual heat in surfacing, or heat transfer through varioguard during the summer months.

Further mitigationBefore installation, it is essential that the main contractor establishes from the surfacing contractor both the asphalt shear data for a static load (as opposed to a wheel load[travelling]), and also details the curing time for the product, at differenttemperatures. This must be factored into the project so that sufficient lead time isallowed prior to installation of Varioguard.



ConclusionIf the A1 joint venture Carillion Morgan Sindall had not installed rubber pads onVarioguard, then hypothetically varioguard had been placed on newly laid surfaceCourse, the cost of resurfacing of two lanes (as varioguard straddles joint line) without pads on newly laid surfacing lanes with longitudinal indentations requiring 160,600 m2 of planning and resurfacing at a cost of £2.4 Million plus attendances.When the tolerance in flatness on the base of varioguard is combined with toleranceIn asphalt surfacing flatness, the surface pressure on the asphalt can be such thatdeformation occurs. The use of the varioguard rubber pads, specifically designed by TRL for use with this product, considerably evens out, and thus effectively reduces the bearing pressure on the asphalt.

For future road projects Carillion Morgan Sindall will not be laying permanent linemarkings prior to installation of varioguard on new surface course, however willalways use rubber pads on newly laid surface course using all the considerationslisted in this document.

© Crown copyright 2012. You may re-use this information (not including logos) free of charge in any format or medium, under the terms of the Open Government Licence. To view this licence, visit http://www.nationalarchives.gov.uk/doc/open-government-licence/ or write to the Information Policy Team, The National Archives, Kew, London TW9 4DU, or email: [email protected].

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