This document is published by National Highways.

Together with CS 229 [Ref 1.I] and CD 227 [Ref 1.N], this document supersedes HD 29/08 and HD 30/08, which are withdrawn.

This document forms part of the works specification. It does not purport to include all the necessary provisions of a contract. Users are responsible for applying all appropriate documents applicable to their contract.

Road pavements do not last indefinitely. At some stage in their lives signs of wear such as polishing, rutting, fretting and cracking may show on the surface. Maintenance is required when these signs of wear are judged to affect the standards of service provided to the road user and the integrity of the pavement structure.

The Overseeing Organisations use a hierarchical approach to assess the needs of the carriageways on motorways and all-purpose trunk roads:

1) Network-level surveys, undertaken on a routine basis, are used to identify lengths of pavement that potentially require maintenance. Wherever possible these surveys are undertaken at traffic speed. The requirements for this process are set out in this document. Requirements to be used to determine and assess skidding resistance on the network are set out in CS 228 [Ref 2.I].

2) Once a length has been identified as requiring maintenance then a detailed investigation is required to determine the maintenance need and to provide the information required to design the appropriate maintenance treatments. The requirements for this process are set out in CD 227 [Ref 1.N].

3) The technical requirements and associated advice for collecting the scheme-level data required to support this process are set out in CS 229 [Ref 1.I].

The assumptions made in GG 101 [Ref 2.N] apply to this document.

Where there is a requirement in this document for compliance with any part of a "British Standard" or other technical specification, that requirement may be met by compliance with the Mutual Recognition clause in GG 101 [Ref 2.N]Introduction to the Design Manual for Roads and Bridges (as the standard text in MDD v6 cl 4.39).

1.1 The requirements in this document shall be used to identify lengths of pavement on the carriageways of the Overseeing Organisations’ motorway and all-purpose trunk road network that require maintenance.

NOTE 1 The requirements for undertaking detailed investigations for determining maintenance need and providing the information required to design the appropriate maintenance treatments are set out in CD 227 [Ref 1.N].

NOTE 2 The technical requirements and associated advice for collecting the scheme-level data required to support the design process are set out in CS 229 [Ref 1.I].

NOTE 3 This document does not cover skid resistance. Requirements for determining and assessing skidding resistance on the network are set out in CS 228 [Ref 2.I].

1.2 This document shall be implemented forthwith on all schemes involving the design of pavement renewals on the Overseeing Organisations’ motorway and all-purpose trunk roads according to the implementation requirements of  GG 101 [Ref 2.N].

1.3 The requirements contained in GG 101 [Ref 2.N] shall be followed in respect of activities covered by this document.

2.2 Surface condition surveys shall be undertaken on the Overseeing Organisations’ motorway and all-purpose trunk roads in accordance with the National Application Annex (NAA).

NOTE 1 Surface condition surveys are undertaken at traffic speed using survey vehicles equipped with sophisticated measurement apparatus.

NOTE 2 Typically surface condition surveys provide data on rutting (transverse profile), ride quality (longitudinal profile), texture depth and road geometry (gradient, crossfall and curvature). They can include collection of forward and downward facing images.

NOTE 3 Some of the data collected by surface condition surveys can be used to provide information on the structural condition of the pavement.

NOTE 4 Skidding resistance is a property of surface condition. This document does not cover skidding resistance. Requirements for determining and assessing skidding resistance on the network are set out in CS 228 [Ref 2.I].

2.3 Structural condition surveys shall be undertaken on the Overseeing Organisations’ motorway and all-purpose trunk roads in accordance with the NAA.

NOTE Typically structural condition surveys provide data on the deflection response of the pavement. This data is used to assess the structural strength of the pavement.

This document is published by National Highways.

Together with CS 229 [Ref 1.N] and CD 227 [Ref 3.N], this document supersedes HD 29/08 and HD 30/08, which are withdrawn.

This revision includes additional requirements for the maintenance of legacy concrete pavements aligned with National Highways concrete roads programme.

This document forms part of the works specification. It does not purport to include all the necessary provisions of a contract. Users are responsible for applying all appropriate documents applicable to their contract.

This National Application Annex gives the National Highways-specific requirements for routine, network-level surveys of pavement surface condition and structural condition. It sets out the requirements for reviewing the outputs from these surveys in order to identify lengths of carriageway that are potentially in need of maintenance and that require a detailed assessment. It does not cover the routine measurement of skidding resistance which is dealt with in CS 228 [Ref 2.I].

This document also sets out the requirements for identifying technically simple pavement schemes (TSS) and lengths that may be suitable for a preventative maintenance treatment using an asphalt preservation system. Technically simple pavement schemes are lengths of carriageway where there are no structural problems i.e. where deterioration is confined to the surface course. These schemes can require renewal of only the surface course and are subject to a simplified development and assessment process. Lengths identified as being suitable for a preventative maintenance treatment using network data are subject to further laboratory investigation as set out in CD 227 [Ref 3.N].

This revision includes additional requirements covering the network level assessment of legacy concrete pavements.

The assumptions made in GG 101 [Ref 4.N] apply to this document.

Where there is a requirement in this document for compliance with any part of a "British Standard" or other technical specification, that requirement may be met by compliance with the mutual recognition clause in GG 101 [Ref 4.N].

E/1.1 Network level surface condition surveys on the National Highways motorway and all-purpose trunk road network shall be undertaken as part of the TRACS4 contract, centrally managed by National Highways.

NOTE 1 TRACS stands for TRAffic-speed condition survey.

NOTE 2 The coverage and frequency of surveys are set out in the TRACS4 contract. TRACS surveys cover all mainline running lanes and lane 1 of slip roads. Roundabouts are not included.

E/1.2 The TRACS vehicles shall be accredited by National Highways for use on their network.

E/1.3 TRACS surveys shall be controlled by a detailed quality audit procedure for the surveys, which includes regular independent checks to maintain quality assurance.

E/1.4 TRACS surveys shall provide the following information about the pavement:

NOTE 1 TRACS data is available in HAPMS and is referenced to the HAPMS network.

NOTE 2 The road geometry measures are used in the classification of site categories for assigning investigatory levels of skidding resistance. See CS 228 [Ref 2.I]

NOTE 3 The TRACS cracking measure was introduced in 2018 and there are currently no guidance levels for interpretation of this parameter.

NOTE 4 TRACS also measures retroreflectivity of road markings. Inspection and maintenance of road markings is covered in CS 126 [Ref 1.I].

NOTE 5 TRACS also collects high quality downward and forward facing images. These images provide information that can be used for detailed visual condition surveys of the carriageway as described in CS 229 [Ref 1.N] and for the network visual assessment of rigid pavements, as described in this document.

NOTE 6 For legacy concrete pavements, condition is assessed centrally by National Highways using condition data derived from a modified analysis of TRACS data.

NOTE 7 Detailed guidance on the TRACS parameters is provided in the TRACS guidance documents available to National Highways staff and authorised service providers.

NOTE 8 Further information is available from the National Highways HAPMS support team (HAST).

E/1.9 TRACS lane fretting Intensity shall be assessed against the guidance values shown in Table E/1.9.

NOTE 1 The categories apply to the 100-m TRACS length weighted (LW) average lane fretting intensity values as reported by HAPMS.

NOTE 2 TRACS lane fretting intensity applies to all asphalt surfaces.

NOTE 3 TRACS lane fretting intensity is reported within the range 0 to 625.

E/1.10 The TRACS bump measure shall be used to identify lengths containing short defects ("bumps") that are not effectively identified from eLPV.

NOTE 1 The parameter is reported from HAPMS as 100-m TRACS length weighted average bump measure.

NOTE 2 "Bumps" can cause jolt-like sensations within vehicles. Examples of "bumps" include sunken ironwork, potholes and poor transverse joints.

NOTE 3 The bump measure is reported as either 0 or 1.1 indicates that the length contains one or more "bumps".

E/1.11 TRACS surface type and noise shall be used to provide additional information about lengths of pavement that have been identified as potentially being in need of maintenance.

E/1.11.1 The TRACS surface type may be used to cross check the accuracy of the surface construction records in HAPMS.

NOTE The TRACS surface type provides a prediction of the surface type based on texture data and luminosity of the surface.

E/1.11.2 The TRACS noise measure may be used to aid the investigation of noise levels.

NOTE The TRACS noise measure provides a prediction of the noise levels generated by the surface/tyre interaction based on texture and the TRACS surface type.

E/1.12 The condition of legacy concrete pavements shall be assessed using condition data that is derived from a modified analysis of TRACS data.

E/1.13 Legacy concrete pavements shall be assigned a state as defined in table E/1.13.

E/1.14 TRACS downward facing images shall be reviewed and used to carry out a network visual condition assessment of each running lane of CRCPs designed in accordance with CD 226 [Ref 2.N].

NOTE The assessment is based on the number of significant defects per 100-m length in each lane (see CS 229 [Ref 1.N] for the definition of significant defects).

E/1.15 A procedure shall be put in place for reviewing all lengths of CRCP at least once every three years.

E/1.15.1 The review may be done by reviewing one third of the length each year or all lengths of CRCP every three years.

E/1.16 The level of visual defects that shall be used to define condition category are given in Table E/1.16.

E/1.17 Network level structural condition surveys on the National Highways motorway and all-purpose trunk road network shall be undertaken as part of the TRASS3 contract, centrally managed by National Highways.

NOTE 1 TRASS stands for TRAffic-speed Structural condition Surveys (TRASS).

NOTE 2 TRASS survey data is only valid for flexible pavements i.e. flexible with an asphalt base and flexible with an HBM base.

NOTE 3 The coverage and frequency of surveys are set out in the TRASS3 contract. TRASS surveys cover lane 1 and lane 2 of mainline and lane 1 of slip roads. Roundabouts are not included.

E/1.18 National Highways' traffic speed deflectometer (TSD) shall be used to carry out the TRASS surveys.

E/1.19 The TSD shall be accredited by National Highways for use on their network.

E/1.20 The TSD surveys shall be controlled by a detailed quality audit procedure for the surveys, which includes regular independent checks to maintain quality assurance.

E/1.21 TRASS surveys shall be used to provide information about the structural condition of flexible pavements.

NOTE TRASS data is available in HAPMS and is referenced to the HAPMS network.

E/1.22 The latest construction and traffic information shall be used when reviewing TRASS data for assessment purposes.

NOTE The robustness of the reported TRASS analysis results are critically dependent on the availability of accurate construction and traffic data in HAPMS.

E/1.23 The results from TRASS shall be assessed against the four network structural condition (NSC) categories defined in Table E/1.22.

NOTE 1 The categories apply to the 100-m TRASS NSC as reported by HAPMS.

NOTE 2 NSC is reported as “null” when it is not possible to complete the analysis procedure satisfactorily; for example where pavement quality concrete is present or where construction and/or traffic data are not available.

NOTE 3 Further information on the use of TRASS NSC categories for determining the need for deflectograph surveys as part of a renewal pavement investigation is given in CD 227 [Ref 3.N].

NOTE 4 Further information on TRASS and the TSD is given in Appendix E/B.

E/2.1 For legacy concrete pavements, condition data shall be reviewed in order to select lengths of the network that are candidates for lifecycle extension works (LEW) ahead of reconstruction.

E/2.2 TRACS and TRASS condition data, obtained from HAPMS, and the additional data described in CS 230 [Ref 5.N] Section 3 shall be collated and reviewed on an annual basis in order to identify lengths of pavement that are showing signs of deterioration.

E/2.3 The review of this data shall be used to select lengths of the network that warrant detailed investigation in order to determine the causes and extent of the deterioration.

NOTE 1 Isolated short (100 m) lengths which are exhibiting slight levels of deterioration are unlikely to require further investigation.

NOTE 2 Lengths that are exhibiting significant levels of deterioration, or adjacent lengths that are exhibiting moderate levels of deterioration, are likely to require further investigation.

E/2.4 For the network review, TRACS condition data (100-m reporting length) shall be obtained from HAPMS using the most recent TRACS length weighted average (LWAVG) data source.

NOTE The HAPMS database contains current and historical TRACS data.

E/2.4.1 TRACS data from earlier surveys may also be used to provide additional information on the rate of change of condition.

NOTE 1 Time series analysis can be useful in determining how quickly pavements are deteriorating.

NOTE 2 Some of the parameters have changed how they are reported over time and it is not appropriate to directly compare values for these parameters.

NOTE 3 Further information on the evolution of the TRACS condition parameters is available to National Highways staff and authorised service providers.

E/2.11 For the network review, TRASS condition data (100-m reporting length) shall be obtained from HAPMS using the most recent TRASS data source.

NOTE The HAPMS database contains current and historical TRASS data.

E/2.12 The structural condition of each 100-m reporting length shall be assigned one of four levels of network structural condition (NSC) category, as defined in Table E/1.22.

NOTE The NSC categories are used:

E/2.13 A review of the network level condition data described in this document and the characteristic skid coefficient data described in CS 228 [Ref 2.I] shall be used to select lengths of the network that warrant further investigation in order to confirm their suitability for receiving a preventative maintenance treatment.

NOTE Preventative maintenance can extend the service life of an existing thin surface course system.

E/2.14 Lengths suitable for investigation for receiving a preventative maintenance treatment shall meet all of the following criteria:

NOTE 1 The initial identification of sites is based on network level data.

NOTE 2 A visual assessment, either a drive-over or a review of video images, can be used to confirm that the length is free of visual defects.

NOTE 3 Assessment of characteristic skid coefficients and investigatory levels is set out in CS 228 [Ref 2.I].

E/2.15 Lengths that are selected from the review shall be subject to laboratory testing to confirm that the TSCS material is suitable to receive a preventative treatment as set out in Section 4 of CD 227 [Ref 3.N].

E/2.16 Technically simple pavement schemes (TSS) require renewal of only the surface course and shall be subject to a simplified development and assessment process.

NOTE 1 TSS are lengths of carriageway where there are no structural problems; that is where pavement deterioration is present but is confined to the surface course.

NOTE 2 It is expected that a TSS can consist of a number of contiguous HAPMS sections that each meet the selection criteria set out in Figure E/2.18.

E/2.16.1 The minimum length of a TSS should be 500 m.

E/2.16.2 All running lanes within the HAPMS sections making up the TSS should have the surface course renewed, apart from substantial, continuous lengths of thin surface course systems (TSCS) that are less than five years old.

E/2.16.3 HAPMS sections that do not meet the TSS criteria (i.e. they include some limited areas that have defects requiring deeper treatments) may be included within a TSS provided that the total works costs of the structural repairs, excluding surface course, are less than 10% of the scheme area and less than £100k for the whole scheme.

E/2.17 TSS shall not include replacement of the surface course of hard shoulders (unless they are a running lane), lengths of pavement over underbridges, or rigid pavement sections (including those with overlays).

E/2.29 Where the decision is taken to proceed with a technically simple pavement scheme, the surfacing shall be designed in accordance with Section 4 of CD 227 [Ref 3.N].

E/2.30 Any short lengths within the technically simple pavement schemes that require deeper treatment (within the £100k limit) shall be designed in accordance with Section 5 of CD 227 [Ref 3.N].

Surveys on the strategic road network in England carried out under the TRAffic-speed condition survey (TRACS) contract commenced in 2000. TRACS surveys are carried out using survey vehicles equipped with lasers, video image collection and inertia measurement apparatus to enable surveys of the road surface condition to be carried out whilst travelling at variable speeds, of up to 100 km/h, to match prevailing traffic, and hence cause minimum disruption to other road users.

As the TRACS contracts have progressed, the parameters measured and reported within HAPMS have changed as technology has moved on. This section provides a short description of each of the main pavement-related parameters reported under the current TRACS contract. More information on HAPMS is available to National Highways staff and authorised service providers.

The surface texture depth measured by TRACS survey vehicles is the coarser element of macrotexture and the finer element of megatexture formed by aggregate particles in the asphalt surfacing or by the brushing or grooving of concrete surfacing. Texture depth contributes to skidding resistance, primarily at medium and high speeds, in two ways. Firstly, it provides drainage paths to allow water to be removed rapidly from the tyre/road interface. Secondly, the projections, which contribute to hysteresis losses in the tyre, are an important factor in the braking process.

The MSP software calculates sensor-measured texture depth (SMTD) from the raw texture profile measurements collected by TRACS survey vehicles for the near side wheel-track, and averages them over 10-m lengths for storage as base data within HAPMS.

To measure rut depth, TRACS survey vehicles record the transverse profile of the road surface at 200 points over a minimum width of 3.8 m using lasers. They also record the road marking profile over a minimum width of 3.8 m and at the same transverse and longitudinal locations as the transverse profile. The 200 transverse profile measurements are processed in MSP, which uses an algorithm to simulate placing a notional 2-m straight edge on the recorded transverse profile, and measuring the largest deviation from the straight edge to the transverse profile, excluding any measurements made on road markings. This calculation is carried out for each wheel-track. MSP calculates the average of the individual rut depths for each wheel-track over 10-m lengths for storage within HAPMS.

The transverse profile measurement method of rut depth determination used by TRACS vehicles has been shown to be highly comparable with the measurements made using a conventional straight edge and wedge.

It is recommended that, where any length has been identified for further investigation as a result of deep rut depths, that comparison be made between the left rut and right rut length weighted average values contained within HAPMS. This is to check that there are no excessive differences which could be caused by the inclusion of the edge line in the left or right rut measurements.

TRACS "lane fretting" has been reported since January 2014. This replaced the TRACS "fretting" parameter which was delivered between June 2004 and January 2014. The older fretting parameter provided an indication of the amount of fretting present on HRA surfaced pavements only and was calculated from the texture profile measured in the left wheelpath.

TRACS lane fretting has been introduced to improve the ability to identify fretting by using multiple lasers across the width of the survey vehicle to provide a measure of the amount of fretting present on the whole lane width. The parameter uses a different approach to calculating fretting so that the measure is able to identify fretting on all asphalt surface types. The values reported by the measure are not comparable to the values reported by the previous single line measure.

The lane fretting algorithm reports the intensity of lane fretting in the range 0 to 625. In general, the higher the value of the fretting parameter, the more likely it is that there is fretting present at that location on the network, and the more severe that fretting is likely to be. However, the way the parameter is calculated means that the values actually quantify how different a local part of the pavement is from its surroundings.

Significant weight should not be unduly applied to moderate proportional differences in the lane fretting Intensity. For example it should not be assumed that lengths with lane fretting of 8 are twice as fretted as lengths with lane fretting of 4. A value of lane fretting of 17.5 in one location is not necessarily more fretted than a value of 16.4 in another place – both locations are probably fretted and should be investigated.

It may not be possible to calculate a value of lane fretting intensity where the survey measurements include a large area of road markings, or where a number of surfacing changes were identified within a short distance of one another, or where the driving line of the survey vehicle deviated from the required survey line and the data were flagged as being out of line by the survey contractor. The values are not to be compared directly with measures obtained from manual visual condition surveys.

Non-invasive information on the structural condition of pavements can be provided from measuring the deflection response under load. These measurements have been provided by the deflectograph and the falling weight deflectometer (FWD). However these devices employ slow-moving (2.5 km/h) or static measurement techniques that require traffic management and cause traffic disruption, which is not ideal for routine network-level assessment.

In 2005, National Highways acquired a traffic speed deflectometer (TSD), developed in Denmark. Following research and development into the operation of this equipment, network-level surveys commenced with this machine on the English strategic road network in 2010 as part of National Highways' first TRAffic-speed structural survey (TRASS) contract.

The TSD comprises a complex array of instruments and recording equipment within an insulated, temperature-controlled, steel container mounted on a single rear axle trailer assembly having a rear axle load of approximately 10 tonnes.

Patented technology uses Doppler lasers, mounted in a stiff frame, to measure the velocity of the deflection of the road surface at three positions in front of the loaded nearside twin rear wheels of the trailer. A fourth velocity sensor, well in front of the loaded wheels, enables corrections to be made for the movement of the vehicle. Other motion sensors enable further corrections for unwanted movement of the mounting frame. Currently the equipment operates at a survey speed of between 50 and 80 km/h, with a target speed of 70 km/h.

The vertical deflection velocity measured at each point is scaled by the instantaneous survey velocity to provide what is known as the TSD “slope”, which is an indicator of the structural strength of the road. This slope is sampled at around 1000 times a second (every 19 mm of travel at 70 km/h) and reported over an average length of one metre.

Although the TSD does not measure the same response to load as the deflectograph, research has shown that a fairly strong relationship exists between the TSD slope and the peak deflection measured by the deflectograph in the nearside wheel-track. The research and development has also continued to identify and implement improvements to the machine operating procedures and its systems to support routine network surveys. These include the addition of a climate control system to reduce the influence of thermal gradients on the measuring beam and more robust distance and survey velocity measuring systems.

TSD surveys are carried out in accordance with standard operating procedures intended to ensure that climatic and machine conditions are suitable for reliable data to be obtained. For example, surveys do not provide valid data when the road surface is wet. The valid operating speed of the TSD has constrained upper and lower limits. This is so that data that is sufficiently robust for network level use can be obtained without need for correction of the results for the effect of vehicle speed.

The analysis of TRASS data is carried out within HAPMS and creates outputs at a base reporting length of 100 m. If the total length of a HAPMS section is not an exact multiple of 100 m then an output is also provided for the final sub-100 m length of the section. The analysis procedure uses an algorithm to convert each of the 1-m TSD slopes in the reporting length to an estimated peak deflectograph value.

The corresponding construction information held in HAPMS is used to calculate the “characteristic base type” (CBT) for each 100-m length. This can be “BITS”, “CEMT” or “GNCA” following the same rules for classifying base types as used for deflectograph analysis in HAPMS as described in CS 229 [Ref 1.N]. The CBT of a reporting length is defined as the base type present for the majority of that length. The estimated peak deflectograph values together with the construction and traffic information are used to calculate the network structural condition (NSC) category as described in Section E/2.

It should be noted that at the present time the analysis does not include correction of TSD slope values for the influence of survey speed or pavement temperature.

Further details of the analysis are provided in the HAPMS documentation, available to National Highways staff and authorised service providers.

The analysis of TRASS survey data is only valid for flexible pavements, with the robustness of the reported results being critically dependent on the availability of accurate construction and traffic data in HAPMS. Service providers should therefore ensure that this information is sufficiently accurate before using TRASS data in the planning of scheme level investigations.

A null NSC category is reported for 100-m lengths when it is not possible for HAPMS to complete the analysis procedure satisfactorily. This includes where valid TSD data are not available for the reporting length. This occurs for HAPMS sections where TRASS surveys have not been undertaken (for example roundabouts) or where the TRASS survey data is invalid (for example if they are undertaken outside of the required speed range). In these cases the TSD slope value is also reported as "null".

While the reported 85th percentile slope values are not currently to be used for maintenance assessment planning, their presence is an indication that valid TRASS data has been collected for the corresponding 100-m length. It is possible for valid TSD data to be present but the NSC category to be reported as "null". This occurs where pavement quality concrete is present, where the construction is too thin to meet the classification criteria for BITS or CEMT base types, or where there is a lack of valid traffic information.

Where the NSC category is reported as null, the construction and traffic data held in HAPMS should be reviewed and updated if appropriate before rerunning the TRASS analysis procedure in HAPMS.

This document is published by National Highways on behalf of the Department for Infrastructure, Northern Ireland.

This document forms part of the works specification. It does not purport to include all the necessary provisions of a contract. Users are responsible for applying all appropriate documents applicable to their contract.

This National Application Annex gives the Department for Infrastructure Northern Ireland-specific requirements for routine, network-level surveys of pavement surface condition and structural condition. It sets out the requirements for reviewing the outputs from these surveys in order to identify lengths of carriageway that are potentially in need of maintenance and that require a detailed assessment. It does not cover the routine measurement of skidding resistance which is dealt with in CS 228 [Ref 6.N].

The assumptions made in GG 101 [Ref 3.N] apply to this document.

NI/1.1 Surface condition surveys of carriageways on the motorway and trunk road network shall preferably be carried out at traffic speed.

NI/1.1.1 Surface condition surveys may be undertaken on foot in agreement with the Department for Infrastructure.

NI/1.2 On the road network in Northern Ireland, traffic-speed surveys shall be carried out on designated roads using the Surface Condition Assessment of the National NEtwork of Roads (SCANNER) system.

NI/1.3 The thresholds, weightings and factors as set out in UKPMS Technical Note 42 Part 2, published on the UK Roads Liaison Group website (see UKRLG TN 42 [Ref 7.N], shall be used in the RCI calculations.

NOTE This survey system had been developed by the UK Roads Board to provide a consistent method of measuring the surface condition of local authority carriageways, using automated road condition survey machines, throughout the UK . Full details are given in the SCANNER Specification [Ref 5.N]and User Guide published by the UK Roads Board.

NI/1.4 Before a survey vehicle can be used to carry out a SCANNER survey, it shall pass accreditation tests each year and be operated with a defined quality assurance procedure with an independent auditor.

NI/1.5 The survey data produced by the survey machines shall be loaded into the pavement management system (PMS) for highway maintenance and management purposes.

NI/1.6 Network level (TRACS) surface condition surveys on designated roads of the Northern Ireland's motorway and all-purpose trunk road network shall be undertaken as per the requirements of the respective network management contract, centrally managed by the Department for Infrastructure.

NOTE 1 TRACS stands for TRAffic-speed Condition Survey.

NOTE 2 The coverage and frequency of surveys are set out in the respective network management contract.

NI/1.7 TRACS vehicles shall be accredited and approved for use by the Overseeing Organisation for use on their network.

NI/1.8 TRACS surveys shall be controlled by a detailed quality audit procedure for the surveys, which includes regular independent checks to maintain quality assurance.

NI/1.9 TRACS surveys shall provide the following information about the pavement:

NOTE 1 TRACS data is available in the PMS and is referenced to the PMS network.

NOTE 2 The road geometry measures are used in the classification of site categories for assigning investigatory levels of skidding resistance provided in DMRB CS 228 [Ref 6.N].

NOTE 3 The TRACS cracking measure was introduced in 2018 and there are currently no guidance levels for interpretation of this parameter.

NOTE 4 TRACS also measures retroreflectivity of road markings. Inspection and maintenance of road markings is covered in CS 126 [Ref 1.I].

NOTE 5 TRACS also collects high quality downward and forward facing images. These images provide information that can be used for detailed visual condition surveys of the carriageway as described in CS 229 [Ref 1.N] and for the network visual assessment of rigid pavements, as described in this document.

NOTE 6 Detailed guidance on the TRACS parameters is provided in the TRACS guidance documents available through National Highways staff at: http://hawacphap013/hapms/.

NI/1.14 TRACS lane fretting Intensity shall be assessed against the guidance values shown in Table NI/1.14.

NOTE 1 The categories apply to the 100-m TRACS length weighted (LW) average lane fretting intensity values as reported by HAPMS.

NOTE 2 TRACS lane fretting intensity applies to all asphalt surfaces.

NOTE 3 TRACS lane fretting intensity is reported within the range 0 to 625.

NI/1.15 The TRACS bump measure shall be used to identify lengths containing short defects ("bumps") that are not effectively identified from eLPV.

NOTE 1 The parameter is reported as 100-m TRACS length weighted average bump measure.

NOTE 2 "Bumps" can cause jolt-like sensations within vehicles. Examples of "bumps" include sunken ironwork, potholes and poor transverse joints.

NOTE 3 The bump measure is reported as either 0 or 1. 1 indicates that the length contains one or more "bumps".

NI/1.16 TRACS surface type and noise shall be used to provide additional information about lengths of pavement that have been identified as potentially being in need of maintenance.

NI/1.16.1 The TRACS surface type provides a prediction of the surface type based on texture data and luminosity of the surface. The measure may be used to cross check the accuracy of the surface construction records in the PMS.

NI/1.16.2 The TRACS noise measure provides a prediction of the noise levels generated by the surface/tyre interaction based on texture and the TRACS surface type. The noise measure may be used to aid the investigation of noise levels.

NI/1.17 TRACS downward facing images shall be reviewed and used to carry out a network visual condition assessment of each running lane for all jointed rigid pavements and continuously reinforced concrete pavements (CRCP).

NOTE 1 For jointed rigid pavements, the assessment is based on the percentage of bays that have cracked, broken or been replaced in each 100-m length in each lane.

NOTE 2 For jointed unreinforced pavements, a bay is considered to be cracked or broken if it contains one or more of the following defects:

NOTE 3 For jointed reinforced pavements, a bay is considered to be cracked or broken when the total length of cracks (>1.5 mm wide) exceeds the width of the bay.

NOTE 4 For CRCP, the assessment is based on the number of significant defects per 100-m length in each lane (see CS 229 [Ref 1.N]] for the definition of significant defects).

NI/1.18 A procedure shall be put in place for reviewing the network at least once every three years.

NOTE The review can be done by reviewing one third of the network each year or all of the network every three years.

NI/1.19 The level of visual defects that shall be used to define condition category are given in Table NI/1.19.

NOTE 1 Categories apply to each 100-m length in each lane in each PMS section.

NOTE 2 The assessment applies to all pavements with a concrete surfacing and to all rigid pavements with asphalt cover of 50 mm or less.

NI/1.20 The results of the assessment shall be uploaded to the PMS.

NI/1.21 Deflectograph surveys shall be carried out in accordance with CS 229 [Ref 1.N] and at the frequency prescribed in network management contracts, for designated roads, or by the Overseeing Organisation's policy for roads managed by the road authority.

NI/1.22 All deflectograph survey data shall be processed centrally through the PMS using the most recent traffic and construction data.

NOTE Further details are available from the Overseeing Organisation.

NI/2.4 The PMS database contains current and historical TRACS data. For the network review, TRACS condition data (100-m reporting length) shall be obtained from the PMS using the most recent TRACS length weighted average (LWAVG) data source.

NI/2.4.1 TRACS data from earlier surveys may also be used to provide additional information on the rate of change of condition.

NOTE 1 Time series analysis can be useful in determining how quickly pavements are deteriorating.

NOTE 2 Some of the parameters have changed how they are reported over time and it is not appropriate to directly compare values for these parameters.

NOTE 3 Further information on the evolution of the TRACS condition parameters is available through contacting National Highways.

TRACS surveys are carried out using survey vehicles equipped with lasers, video image collection and inertia measurement apparatus to enable surveys of the road surface condition to be carried out whilst travelling at variable speeds, of up to 100km/h, to match prevailing traffic, and hence cause minimum disruption to other road users.

This section provides a short description of each of the main pavement-related parameters reported under the current TRACS contract.

The surface texture depth measured by TRACS survey vehicles is the coarser element of macrotexture and the finer element of megatexture formed by aggregate particles in the asphalt surfacing or by the brushing or grooving of concrete surfacing. Texture depth contributes to skidding resistance, primarily at medium and high speeds, in two ways. Firstly, it provides drainage paths to allow water to be removed rapidly from the tyre/road interface. Secondly, the projections, which contribute to hysteresis losses in the tyre, are an important factor in the braking process.

The MSP software calculates sensor measured texture depth (SMTD) from the raw texture profile measurements collected by TRACS survey vehicles for the near side wheel-track and averages them over 10-m lengths for storage as base data within the PMS.

To measure rut depth, TRACS survey vehicles record the transverse profile of the road surface at 200 points over a minimum width of 3.8 m using lasers. They also record the road marking profile over a minimum width of 3.8 m and at the same transverse and longitudinal locations as the transverse profile. The 200 transverse profile measurements are processed in MSP, which uses an algorithm to simulate placing a notional 2-m straight edge on the recorded transverse profile, and measuring the largest deviation from the straight edge to the transverse profile, excluding any measurements made on road markings. This calculation is carried out for each wheel-track. MSP calculates the average of the individual rut depths for each wheel-track over 10-m lengths for storage within the PMS.

The transverse profile measurement method of rut depth determination used by TRACS vehicles has been shown to be highly comparable with the measurements made using a conventional straight edge and wedge.

It is recommended that, where any length has been identified for further investigation as a result of deep rut depths, that comparison be made between the left rut and right rut length weighted average values contained within the PMS. This is to check that there are no excessive differences which could be caused by the inclusion of the edge line in the left or right rut measurements.

TRACS "lane fretting" has been reported since January 2014. This replaced the TRACS "fretting" parameter which was delivered between June 2004 and January 2014. The older fretting parameter provided an indication of the amount of fretting present on HRA surfaced pavements only and was calculated from the texture profile measured in the left wheeltrack.

TRACS lane fretting has been introduced to improve the ability to identify fretting by using multiple lasers across the width of the survey vehicle to provide a measure of the amount of fretting present on the whole lane width. The parameter uses a different approach to calculating fretting so that the measure is able to identify fretting on all asphalt surface types. The values reported by the measure are not comparable to the values reported by the previous single line measure.

The lane fretting algorithm reports the intensity of lane fretting in the range 0 to 625. In general, the higher the value of the fretting parameter, the more likely it is that there is fretting present at that location on the network, and the more severe that fretting is likely to be. However, the way the parameter is calculated means that the values actually quantify how different a local part of the pavement is from its surroundings.

Significant weight should not be unduly applied to moderate proportional differences in the lane fretting Intensity. For example it should not be assumed that lengths with lane fretting of 8 are twice as fretted as lengths with lane fretting of 4. A value of lane fretting of 17.5 in one location is not necessarily more fretted than a value of 16.4 in another place – both locations are probably fretted and should be investigated.

It may not be possible to calculate a value of lane fretting intensity where the survey measurements include a large area of road markings, or where a number of surfacing changes were identified within a short distance of one another, or where the driving line of the survey vehicle deviated from the required survey line and the data were flagged as being out of line by the survey contractor. The values are not to be compared directly with measures obtained from manual visual condition surveys.

This document is published by National Highways on behalf of Transport Scotland.

Together with DMRB CS 229 [Ref 1.N] and CD 227 [Ref 2.N], this document supersedes HD 29/08 and HD 30/08, which are withdrawn.

This document forms part of the works specification. It does not purport to include all the necessary provisions of a contract. Users are responsible for applying all appropriate documents applicable to their contract.

This national application annex gives the Transport Scotland-specific requirements for routine, network-level surveys of pavement surface condition and structural condition. It sets out the requirements for reviewing the outputs from these surveys in order to identify lengths of carriageway that are potentially in need of maintenance and that require a detailed assessment. It does not cover the routine measurement of skidding resistance, which is dealt with in DMRB CS 228 [Ref 6.N].

This document also sets out the requirements for identifying technically simple pavement schemes (TSS). Technically simple pavement schemes are lengths of carriageway where there are no structural problems i.e. where deterioration is confined to the surface course. These schemes will require renewal of only the surface course and are subject to a simplified development and assessment process.

The assumptions made in GG 101 [Ref 4.N] apply to this document.

S/1.1 On the National Network in Scotland, traffic-speed surveys shall be carried out using the Surface Condition Assessment of the National Network of Roads (SCANNER) system.

NOTE This survey system had been developed by the UK Roads Board to provide a consistent method of measuring the surface condition of Local Authority carriageways, using automated road condition survey machines, throughout the UK . Full details are given in the five-volume User Guide and Specifications published by the UK Roads Board (2007).

S/1.2 Before a survey vehicle can be used to carry out a SCANNER survey, it shall pass accreditation tests each year and be operated with a defined quality assurance procedure with an independent auditor.

S/1.3 The survey data produced by the survey machines shall be loaded into the pavement management system (PMS) for highway maintenance and management purposes.

S/1.4 SCANNER surveys of the Trunk Road network shall commence no earlier than the 1st April and are to be completed by the 30th June each year.

S/1.5 The SCANNER texture depth, rut depth, longitudinal profile variation and cracking survey data shall be assessed against the three condition categories defined in Table S/1.5.

This document is published by National Highways on behalf of the Welsh Government.

Together with DMRB CS 229 [Ref 1.N] and CD 227 [Ref 2.N], this document supersedes HD 29/08 and HD 30/08, which are withdrawn.

This document forms part of the works specification. It does not purport to include all the necessary provisions of a contract. Users are responsible for applying all appropriate documents applicable to their contract.

This national application annex gives the Welsh Government (WG) requirements for routine, network-level surveys of pavement surface condition and structural condition. It sets out the requirements for reviewing the outputs from these surveys in order to identify lengths of carriageway that are potentially in need of maintenance and that require a detailed assessment. It does not cover the routine measurement of skidding resistance which is dealt with in DMRB CS 228 [Ref 1.I].

This document also sets out the requirements for identifying technically simple pavement schemes (TSS). Technically simple pavement schemes are lengths of carriageway where there are minimal structural problems i.e. where deterioration is mainly confined to the surface course. These schemes will require renewal of the surface course and are subject to a simplified development and assessment process.

The assumptions made in GG 101 [Ref 3.N] apply to this document.

W/1.1 Network level road condition surveys on the WG motorway and all-purpose trunk road network, shall be undertaken as part of the Integrated Roads Information System (IRIS) contract or future alternatives managed by Welsh Government.

W/1.2 Network level road condition surveys shall include:

NOTE 1 SCANNER has been developed by the UK Roads Board (now UKRLG) to provide a consistent method of measuring the surface condition of carriageways. Full details are given in the 5-volume User Guide and Specifications published by the UK Roads Board (2011).

NOTE 2 Details of accredited devices are available on the UKRLG website at the following link: https://ukrlg.ciht.org.uk/ukrlg-home/guidance/road-condition-information/data-collection/scanner/

NOTE 3 The survey coverage and frequency are documented in the IRIS contract. These network level surveys will be undertaken as follows:

W/1.3 All survey data produced by the survey shall be capable of being loaded into IRIS and be controlled by a detailed quality assurance procedure for the surveys, which includes the processing of the survey data.

W/1.4 The SCANNER surveys will be undertaken within the appropriate financial year; however, no surveys shall be be undertaken in December and January unless explicitly agreed by WG.

W/1.5 The SCANNER survey shall capture the full list of parameters detailed in the SCANNER specifications, including:

NOTE Road geometry measurements are used to assist in the assessment of site category and investigatory levels of skidding resistance. See DMRB CS 228 [Ref 1.I].

W/1.6 Primary reporting from SCANNER shall be the 10-m data, and 100-m summary data. The 10-m data will be used for asset management purposes, and the 100-m data used with other condition data for the management of works programmes.

W/1.7 The SCANNER rut depth, texture depth, longitudinal profile variance (LPV) and cracking data shall be assessed individually and collectively against the three condition categories defined in Table W/1.7.

W/1.10 The values to define condition category for LPV, shall be in accordance with Tables W1.10 a&b below.

W/2.4 Only the most current data available from IRIS PMS, must be used for the initial network review.

W/2.4.1 Previous year's data may be used to provide an indication of the rate of change of condition.

NOTE 1 Deterioration modelling can be useful in determining how quickly pavements can deteriorate.

NOTE 2 Some of the parameters have changed how they are reported over time and it is not appropriate to directly compare values for these parameters.

NOTE 3 The analysis of the rate of change of data over time is an excellent way of determining deterioration, as is the use of additional data sets that can be derived from the raw data collected by SCANNER survey vehicles.

W/2.8 For the network review, Deflectograph condition data (100-m reporting length) shall be obtained from IRIS PMS using the most recent deflectograph data source.

NOTE The IRIS PMS database contains current and historical deflectograph data.

W/2.9 The structural condition of each 100-m reporting length shall be assigned one of the five levels of structural condition as defined in Table W/1.22.

NOTE Deflectograph survey data can be used to assist in the identification of pavement schemes.

W/2.10 Technically simple pavement schemes (TSS) are lengths of carriageway where there are no structural problems, i.e. where pavement deterioration is present but is confined to the upper layers. These schemes require renewal of only the surface and binder course and shall be subject to a simplified development and assessment process.

NOTE Isolated areas of structural deterioration that require deeper treatment can be included within TSS, provided they are less than 10% of the scheme area.

W/2.11 TSS shall not include lengths of pavement over structures or rigid pavement (including those with overlays).

W/2.14 Where the decision is taken to proceed with a technically simple pavement scheme, the surfacing shall be designed in accordance with Section 4 of CD 227 [Ref 2.N].

W/2.15 Any short lengths within the technically simple pavement schemes that require deeper treatment (within the limits of W/2.22) shall be designed in accordance with Section 5 of CD 227 [Ref 2.N].

NOTE All planned schemes are listed and prioritised within the 'WG Value Management Process, which can be provided upon request to WG Pavement Team.

The surface texture depth measured by SCANNER survey vehicles is the coarser element of macro-texture and the finer element of megatexture formed by aggregate particles in the asphalt surfacing or by the brushing or grooving of concrete surfacing. Texture depth contributes to skidding resistance, primarily at medium and high speeds, in two ways. Firstly, it provides drainage paths to allow water to be removed rapidly from the tyre/road interface. Secondly, the projections, which contribute to hysteresis losses in the tyre, are an important factor in the braking process. The UKPMS software calculates sensor measured texture depth (SMTD) from the raw texture profile measurements collected by SCANNER survey vehicles for the near side wheel-track and averages them over 10-m lengths for storage as base data within the PMS database.

To measure rut depth, SCANNER survey vehicles use scanning lasers to record the transverse profile of the road surface at a minimum of 22 points over a minimum width of 3.2 m and a maximum width of 3.8 m. The transverse profile measurements are processed, using an algorithm to simulate placing a notional 2-m straight edge on the recorded transverse profile, and measuring the largest deviation from the straight edge to the transverse profile, excluding any measurements made on road markings. This calculation is carried out for each wheel-track. The software calculates the average of the individual rut depths for each wheel-track over 10-m lengths for storage within the client’s PMS.

The transverse profile measurement method of rut depth determination used by SCANNER vehicles has been shown to be highly comparable with the measurements made using a conventional straight edge and wedge.

It is recommended that, where any length has been identified for further investigation as a result of deep rut depths, that comparison be made between the left rut and right rut length weighted average values contained within the PMS database. This is to check that there are no excessive differences which could be caused by the inclusion of the edge line or verge in the left or right rut measurements

The main parameter currently used for the assessment of ride quality, or profile unevenness, is the enhanced longitudinal profile variance (LPV) of individual deviations of the profile relative to a datum obtained by removing (or filtering) longer wavelengths from the measured longitudinal profile.

For example, the variance of deviations from a 3-m filter reflects the unevenness of profile features with wavelengths equal to or less than approximately 3 m. The measurement of profile unevenness can be used to investigate the ride quality of the pavement. The short, medium and long wavelength features that are found to relate with the perceived effect on vehicle ride are represented by variance from 3-m, 10-m and 30-m filters respectively. Due to the nature of the A Road network the 30-m filter is not recommended for use, but it can still be derived from the raw data if required. LPV values are calculated from the SCANNER longitudinal profile measurements by the processing software and averaged over 10 m lengths for storage within PMS database.

Extremes of 3 m LPV may arise from poor reinstatements along the wheel-track, the presence of high and/or variable levels of rutting, and indicate localised failures on evolved rural roads. Extremes of 10 m LPV may also arise from poor reinstatements along the wheel-track, the presence of high and/or variable levels of rutting, the presence of inverted crowns or cambers around junctions and underlying substrate issues on evolved rural roads. High levels of 30 m enhanced longitudinal profile variance may be associated with subsidence particularly in areas of high/fluctuating water tables.

High levels of profile unevenness, particularly in the 3-m and 10-m wavelength ranges, have been shown to contribute to increased dynamic loading of the pavement, hence accelerating the deterioration of the road pavement. Extremes of profile unevenness can also lead to increased stopping distances, and can have an adverse effect on vehicle manoeuvrability and safety.

Research carried out on SCANNER measurements has shown that some SCANNER survey vehicles provide LPV data having lower levels of accuracy when surveying at slow speed, or under conditions of significant acceleration or (more commonly) deceleration. To reduce the occurrence of low accuracy data, limits have been specified for the SCANNER surveys for speed and acceleration/deceleration beyond which the data is considered invalid. These limits will be shown on the TRL Accreditation Certificate for the survey vehicle and will potentially affect the survey coverage and potentially compliance with Table 4.12 of the SCANNER Specification.

The latest NH TRACS specification has introduced a measure for lane fretting intensity, the width of the survey vehicle to provide a measure of the amount of fretting present on the whole lane width. The parameter uses an approach to calculating fretting that is able to identify fretting on all asphalt surface types and is able to quantify how different a local part of the pavement is from its surroundings.

Depending on the survey machine set up it is possible to derive a lane fretting intensity from SCANNER survey data.