Regional Road Network

Home , Kilkenny, Regional road (Ireland), Roads in Ireland

REGIONAL ROAD NETWORK

Pavement Condition Study Report

September 2019

Department of Transport, Tourism and Sport

DOCUMENT CONTROL SHEET

Client Department of Transport, Tourism and Sport

Project Title Regional Roads Condition Study

Document Title Pavement Condition Study Report

Document No. Final Report v4.6 No. of This Document DCS TOC Text Tables Figures Appendices Comprises 1 1 50 14 20 4

Approved Rev. Status Author(s) Reviewed By Office of Origin Issue Date By Client A01 K. Feighan G. O’Dea KJF Dublin 08 Apr 19 Approval Client A02 K. Feighan B. Mulry KJF Dublin 26 Apr 19 Approval Client F01 K. Feighan B. Mulry KJF Dublin 18 Jun 19 Approval Client F02 K. Feighan B. Mulry KJF Dublin 30 Jun 19 Approval Final S. Flynn F03 K. Feighan B. Mulry Dublin 24 Sep 19 Issue RMO

Regional Roads Condition Study 2018 1

TABLE OF CONTENTS

SECTION 0: EXECUTIVE SUMMARY ...... 9

SECTION 1: INTRODUCTION AND BACKGROUND ...... 11

1.1 DTTAS REQUIREMENTS...... 11

1.2 ROAD SCHEDULE ...... 13

1.3 DATA ENTRY AND POST-PROCESSING ...... 16 1.3.1 Visual Rating Software ...... 16 1.3.2 IRI, Rut depth, MPD, LPV3 and CSC Post-Processing ...... 17

1.4 LOADING OF DATABASE ...... 17

SECTION 2: CONDITION PARAMETERS AND CONDITION CLASSES ...... 18

2.1 ROAD CONDITION DATA ...... 18

2.2 VISUAL CONDITION ...... 19

2.3 RATING PAVEMENT SURFACE CONDITION OF REGIONAL ROADS ...... 20

2.4 INTERNATIONAL ROUGHNESS INDEX (IRI) ...... 21

2.5 RUT DEPTH ...... 22

2.6 SURFACE TEXTURE ...... 23

2.7 SKIDDING RESISTANCE ...... 23

2.8 CONDITION CLASSES ...... 24

SECTION 3: REPORTING OF NATIONAL RESULTS ...... 25

3.1 GENERAL STATISTICS ...... 25

3.2 SUBGROUP OBSERVATIONS ...... 29

SECTION 4: RESULTS BY LOCAL AUTHORITY 2018 ...... 34

4.1 GENERAL STATISTICS BY COUNTY ...... 34

SECTION 5: REMEDIAL WORKS CATEGORIES ...... 44

5.1 DESCRIPTION OF REMEDIAL WORKS CATEGORIES ...... 44

5.2 ALLOCATION OF SAMPLE UNITS INTO MAINTENANCE CATEGORIES – 2018 METHODOLOGY ...... 45 5.2.1 Road Reconstruction ...... 46 5.2.2 Structural Rehabilitation ...... 47

Regional Roads Condition Study 2018 2

5.2.3 Surface Restoration ...... 47 5.2.4 Restoration of Skid Resistance ...... 47 5.2.5 Routine Maintenance ...... 48

SECTION 6: REMEDIAL WORKS REQUIREMENTS...... 49

6.1 NATIONAL REQUIREMENTS...... 49

6.2 REMEDIAL REQUIREMENTS BY LOCAL AUTHORITY ...... 50

Regional Roads Condition Study 2018 3

LIST OF FIGURES

Figure 1.1: Regional Road Network in Ireland ...... 13

Figure 1.2: Road Width Cumulative Frequency...... 16

Figure 2.1: PSCI Rating 1 to 10 ...... 20

Figure 3.1: Average IRI Cumulative Frequency Plot ...... 26

Figure 3.2: Left Rut Cumulative Frequency Plot ...... 27

Figure 3.3: Mean Profile Depth (mm) Cumulative Frequency Plot ...... 27

Figure 3.4: SCRIM CSC Cumulative Frequency Plot ...... 28

Figure 3.5: PSCI Cumulative Frequency Plot ...... 29

Figure 3.6: IRI Distributions by Subgroup ...... 31

Figure 3.7: Rut Depth Distributions by Subgroup ...... 32

Figure 3.8: CSC Distributions by Subgroup ...... 32

Figure 3.9: PSCI Distributions by Subgroup ...... 33

Figure 4.1: IRI (% Fair or Better) by Local Authority, 2018 ...... 36

Figure 4.2: Rut Depth (% Fair or Better) by Local Authority, 2018 ...... 38

Figure 4.3: PSCI (% with Rating of 5 or Better) by Local Authority, 2018 ...... 40

Figure 4.4: CSC (% Fair or Better) by Local Authority, 2018 ...... 42

Figure 4.5: Macrotexture (% < 0.6 mm) by Local Authority, 2018 ...... 43

Figure 5.1: Treatment/Works Type Categories ...... 44

Figure 6.1: 2018 Remedial Works Categories ...... 49

Figure 6.2: 2018 Structural Rehabilitation Requirements ...... 51

Regional Roads Condition Study 2018 4

LIST OF TABLES

Table 1.1: Regional Road Length (kilometres) surveyed by Local Authority ...... 14

Table 1.2: Average Regional Road Width (metres) surveyed by Local Authority ...... 15

Table 2.1: IRI Scale ...... 22

Table 2.2: Condition Class Definitions, 2018 ...... 24

Table 3.1: Average Performance Parameters, 2018 ...... 25

Table 3.2: Average Performance Parameters, 2011 ...... 25

Table 3.3: Subgroup Lengths by Local Authority ...... 31

Table 4.1: Condition Parameters – Average Values 2018 ...... 34

Table 4.2: IRI – Condition Classes by Local Authority 2018 ...... 35

Table 4.3: Rut Depth – Condition Classes by Local Authority 2018 ...... 37

Table 4.4: PSCI – Condition Classes by Local Authority 2018...... 39

Table 4.5: SCRIM CSC – Condition Classes by Local Authority 2018 ...... 41

Table 6.1: Maintenance Categories - % in 2018 ...... 49

Table 6.2: Percentage length of Regional Roads in each Remedial Work Category ...... 51

Regional Roads Condition Study 2018 5

APPENDICES

APPENDIX A: NATIONAL COMPARISONS: 2011 TO 2018

APPENDIX B: LOCAL AUTHORITY COMPARISONS: 2011 TO 2018

APPENDIX C: AVERAGE CONDITIONS BY ROUTE

APPENDIX D: EQUIPMENT USED IN 2018 SURVEY

Regional Roads Condition Study 2018 6

LIST OF ACRONYMS

ASTM - American Society for Testing and Materials CSC – Characteristic SCRIM Coefficient DMI – Distance Measuring Instrument DTTAS – Department of Transport, Tourism & Sport DV – Digital Video GIS – Geographic Information System GPS – Global Positioning System GSI – Geological Survey Ireland INAB – Irish National Accreditation Board INS – Inertial Navigation System

IRI – International Roughness Index ITM – Irish Transverse Mercator LGMA – Local Government Management Agency LPV – Longitudinal Profile Variance MPD – Mean Profile Depth OSI – Ordinance Survey Ireland PMS – Pavement Management Services Ltd. PSCI – Pavement Surface Condition Index RCD – Road Condition Data RMO – Road Management Office RSP – Road Surface Profiler RUT – Rut Depth SCRIM – Sideway-force Coefficient Routine Investigation Machine SFC – Sideway-force Coefficient SR – SCRIM Reading SQL – Standardised Query Language TRL – Transport Research Laboratory TII – Transport Infrastructure Ireland

Regional Roads Condition Study 2018 7

VR – Visual Rating ArcGIS – Geographic Information System

Regional Roads Condition Study 2018 8

SECTION 0: EXECUTIVE SUMMARY

The Department of Transport, Tourism and Sport (DTTAS) contracted with PMS Pavement Management Services Ltd (PMS) to carry out a pavement condition study on the entire Regional road network in 2018. The contract was administered by the Road Management Office (RMO) on behalf of DTTAS. The pavement condition study involved the use of machine surveys to collect road condition data, skidding resistance data and digital imagery on the Regional road network. The main objective of the 2018 Pavement Condition Study, carried out under the “Contract for the Provision of Road Condition Survey and Assessment/Analysis of the Regional Road Network”, was to establish, by local authority and nationally, the lengths and areas of various categories of Regional roads requiring remedial works.

A total of 13,150 kilometres comprising 686 Regional road routes was surveyed in one direction as part of the 2018 study. The pavement condition data was collected in accordance with the “Mechanical Road Condition Survey Specification for Regional and Local Roads in Ireland” The road condition data (RCD) was collected using two Road Surface Profiler (RSP) machines. The skidding resistance data was collected using two Sideway-force Coefficient Routine Investigation Machines (SCRIM). The data collection of the road condition data was completed over a 26 week period from April to September 2018. A detailed description of the equipment used is contained in Appendix D of this report.

The outturn condition parameters comprised a number of key pavement performance indicators. The key indicators were visual rating (PSCI), international roughness index (IRI), rut depth, mean profile depth (MPD) and characteristic SCRIM coefficient (CSC). The condition parameters are reported for each 100 metre length of the entire Regional road network. The visual rating was carried out from high definition video used to capture the road surface condition and using the Pavement Surface Condition Index (PSCI) 1 to 10 rating system. Section 3 of this report sets out the main findings on pavement condition at National level in 2018, while Appendix A compares the results from the 2011 and 2018 surveys at National level.

In line with best practice internationally, five condition classes, namely Very Good, Good, Fair, Poor and Very Poor, have been defined for many of the technical parameters. The condition classes are used in Section 4 of this report to characterise the performance of local authority Regional roads in 2018. Appendix B contains a comparison of local authority Regional road pavement conditions in 2011 and 2018.

Regional Roads Condition Study 2018 9

The remedial works categories considered in this report are set out and defined in Section 5. These are Routine Maintenance, Restoration of Skid Resistance, Surface Restoration, Structural Overlay and Road Reconstruction. These categories align with the five categories defined in the Pavement Survey Standard for Regional and Local Roads published by DTTAS in February 2018. The assignment of each surveyed sample unit to one of the remedial works categories is based on visual PSCI rating, with additional consideration of the machine data parameters of IRI, rut depth, MPD and CSC.

Section 6 outlines the percentage of the Regional road network in each of the 5 remedial works categories nationally in 2018. It further tabulates, for each local authority, the percentage in each remedial works category.

Regional Roads Condition Study 2018 10

SECTION 1: INTRODUCTION AND BACKGROUND

1.1 DTTAS REQUIREMENTS

The Department of Transport, Tourism and Sport (DTTAS) contracted with PMS Pavement Management Services Ltd. to carry out a pavement condition study on the Regional roads network in 2018. The pavement condition study comprised the use of machine surveys to collect pavement condition, skidding resistance data and digital imagery on the Regional roads network. The project specification states that “The Regional roads play a vital role in the development of key economic sectors such as industry, tourism and agriculture. In addition, the Regional roads provide mobility within and between local economies and are an important link to the national road network and to Ireland’s ports and airports which provide access to the wider European economy.”

The Regional road network comprises 686 routes totalling 13,150 kilometres of Regional road. This equates to about 15% of the entire non-national network. The main objective of the 2018 Regional Road Pavement Condition Study was to establish the lengths, average width and areas of Regional roads that require various types of remedial works. The lengths and areas were to be established nationally, and on a county-by-county basis. Under the study, the entire Regional road network would be surveyed for road condition and skidding resistance data.

The 2018 study consisted of the following data collection elements and project deliverables:

1. Complete fieldwork for SCRIM survey and associated video, capture and submission of raw data to the client. 2. Complete fieldwork for profile, texture and video surveys and submission of raw data to client. 3. Complete SCRIM data processing and video, and import into MapRoad system. 4. Complete data processing for profile and texture surveys and video and import into MapRoad system.

Another key objective was to compare the results of the 2018 Regional roads study with the results from the previous Regional roads study carried out in 2011. In addition, there were key requirements on the assessment/analysis reporting as follows:

Regional Roads Condition Study 2018 11

1. Review the parameters and remedial works categories and indicators previously developed by DTTAS and set out in the May 2012 Regional Road Network Pavement Condition Survey report. 2. Develop and make recommendations for consideration and agreement by DTTAS for the updating of these parameters, categories and indicators and /or the recording or calculation of additional parameters, categories or indicators.

This information is required both to quantify the current status of road conditions within counties and nationally, and to provide a benchmark measurement to compare against future Regional road survey outcomes.

Finally, it was a requirement that all survey data collected should be available in electronic format, and further that, where appropriate, maximum use was to be made of the Local Government Management Agency (LGMA) MapRoad system as this is already installed in all local authorities and provides the most appropriate and most efficient means of distribution of the collected data at local authority level.

Regional Roads Condition Study 2018 12

1.2 ROAD SCHEDULE

A full road schedule, listing all of the road sections in each local authority using a standardised road numbering system, was supplied by the Road Management Office (RMO). Figure 1.1 shows the Regional road network with just over 13,000 centreline kilometres of roadway.

Figure 1.1: Regional Road Network in Ireland

Regional Roads Condition Study 2018 13

Local Authority Length (km) CARLOW 185 CAVAN 400 CLARE 633 CORK 1368 CORK CITY 37 DUBLIN CITY 200 DUN LAOGHAIRE RATHDOWN 103 DONEGAL 782 FINGAL 254 GALWAY CITY 37 GALWAY 894 KERRY 529 KILDARE 493 KILKENNY 421 LAOIS 348 LEITRIM 332 LIMERICK 531 LONGFORD 151 LOUTH 274 MAYO 623 MEATH 575 MONAGHAN 297 OFFALY 392 ROSCOMMON 375 SLIGO 235 STH DUBLIN 116 TIPPERARY 894 WATERFORD 425 WESTMEATH 313 WEXFORD 475 WICKLOW 460 13150

Table 1.1: Regional Road Length (kilometres) surveyed by Local Authority

Table 1.1 shows the total length of Regional road surveyed in each local authority. For each road section, information was typically provided on the road number, road name, engineering area, descriptions of the start and end of the section, and the length and average width of the road. A unified GIS database showing all of the Regional roads with associated characteristics was provided by the RMO after extraction from each local authority’s MapRoad system.

Regional Roads Condition Study 2018 14

Aver- age Local Authority Road Width (m) CARLOW 7.30 CAVAN 6.91 CLARE 6.77 CORK 7.11 CORK CITY 9.35 DUBLIN CITY 10.19 DUN LAOGHAIRE RATHDOWN 8.71 DONEGAL 6.69 FINGAL 7.96 GALWAY CITY 9.15 GALWAY 7.09 KERRY 6.79 KILDARE 7.90 KILKENNY 7.34 LAOIS 7.60 LEITRIM 6.79 LIMERICK 7.20 LONGFORD 6.82 LOUTH 7.91 MAYO 6.72 MEATH 7.60 MONAGHAN 7.10 OFFALY 7.10 ROSCOMMON 6.96 SLIGO 6.92 STH DUBLIN 9.12 TIPPERARY 7.34 WATERFORD 7.39 WESTMEATH 7.51 WEXFORD 7.08 WICKLOW 6.86 Weighted Average 7.53

Table 1.2: Average Regional Road Width (metres) surveyed by Local Authority

The road width was measured at 100 metre lengths over the entire Regional road network in 2018. The average Regional road width by local authority in 2018 is shown in Table 1.2. The detailed road widths along each route are loaded into MapRoad and are available as a significant additional resource for use by the local authorities. A summary of the average road width on each Regional road is included in Appendix C of this report.

Regional Roads Condition Study 2018 15

Figure 1.2: Road Width Cumulative Frequency

Figure 1.2 shows the distribution of road widths across the Regional road network. It can be seen that c.14% of Regional roads have road widths of less than 6 metres. Around two thirds of the network has a road width between 6 and 8 metres, and this is also clearly reflected in the average road width by local authority in Table 1.2. The remaining 20% of the network shows considerably variability in road width, ranging from 8 to 14 metres.

1.3 DATA ENTRY AND POST-PROCESSING

1.3.1 Visual Rating Software

The rating of the Regional roads was carried out by PMS in-house personnel. The raters were provided with copies of the 1 to 10 PSCI survey manuals and data entry software to allow time for familiarisation. Training on details of distress identification, allocation of the 1 to 10 rating system, the remedial works categories and the rating software was carried out with the rating personnel. Clarification of the details of distress identification, followed by further rating inspections, was performed until all survey raters were producing consistent and repeatable survey results. A series of video clips of standardised road sections was developed, and all survey personnel rated the clips independently.

Regional Roads Condition Study 2018 16

Training and feedback continued until all personnel were rating the road conditions consistently.

To ensure consistency across all raters for the full c.13,000 km of Regional road, common stretches of Regional road were rated independently by all personnel and detailed analysis and comparison of the results was continually carried out to ensure consistent and repeatable survey results.

1.3.2 IRI, Rut depth, MPD, LPV3 and CSC Post-Processing

When the data is being collected in the field, data is collected and averaged over each 10 metre stretch. This raw data has been stored and is available for further detailed analysis if necessary. For the purposes of reporting, the 10 metre data is averaged over each 100 metre length, typically referred to as a 100 metre sample unit. This 100 metre reporting length is similar to the reporting of the National road data by Transport Infrastructure Ireland. Each 100 metre sample unit is separately referenced by local authority and road number. The start and end chainage, and the start and end georeferences in Irish Transverse Mercator (ITM) co-ordinates are also stored to allow multiple sorting and querying in SQL and GIS databases.

1.4 LOADING OF DATABASE

All of the post-processed condition data, as outlined in section 1.3 above, was loaded into a Microsoft Access database. Effectively, there are three key tables. The first table contains the Road Condition Data for every sample unit derived from the RSP survey. The second table contains the processed SCRIM results for every sample unit. The third table contains the Visual Rating (PSCI) results for every sample unit. There are a total of over 130,000 sample units with PSCI, IRI, CSC, LPV3, MPD and rut depth data in the final database. The process of uploading the data was extremely straightforward, and customised queries of the data tables were then defined within Microsoft Access to form the basis for the analysis, tables and figures set out in the remainder of this report. In addition, it is straightforward to export data on an individual local authority basis in SQL or Excel format. Furthermore, the structure of the final database is fully compatible with the requirements of the LGMA MapRoad software package.

Regional Roads Condition Study 2018 17

SECTION 2: CONDITION PARAMETERS AND CONDITION CLASSES

The pavement condition of the entire Regional road network was assessed in 2018 using the SCRIM and RSP machines. The outturn condition parameters comprised a number of key pavement performance indicators. The key indicators were visual rating (VR) now commonly known as pavement surface condition index (PSCI), international roughness index (IRI), rut depth, mean profile depth (MPD), and Characteristic SCRIM coefficient (CSC). The condition parameters are reported for each 100 metre length of the entire Regional road network.

2.1 ROAD CONDITION DATA

In common with the DTTAS 2011 Regional Road Survey, the 2018 survey is based principally around machine-based data. The project consisted of the collection of machine-based road condition and skidding resistance data on the entire Regional road network in one direction. The survey consisted of the following data collection elements:

1. Road Condition Data (RCD) and Skidding resistance data collection on the entire Regional road network 2. Provision of highly accurate 3D GPS traces of the network 3. Provision of digital video to a high quality and consistent standard

The road condition data (RCD) was collected using the Road Surface Profiler (RSP) machine. The skidding resistance data was collected using the Sideway-force Coefficient Routine Investigation Machine (SCRIM). The RSP and SCRIM machines are described in Appendix D.

The RSP machine provided the following survey data:

• 3 dimensional Spatial Co-ordinates (GPS) • Longitudinal profile (Raw) • Longitudinal profile parameters including International Roughness Index (IRI), 3 metre Variance (LPV3), 10 metre Variance (LPV10) • Transverse Profile (Raw) • Transverse profile parameters including Rut Depth, Shape Index and Edge Detection on narrow roads • Surface Texture (mean profile depth, MPD)

Regional Roads Condition Study 2018 18

• Pavement-Oriented Digital Video for Pavement Surface Condition Index Rating

The SCRIM equipment provided the following survey data for each 10m sub-section length:

• SCRIM Reading (SR) • Average speed, in km/h • Right of Way-Oriented Digital Video • Elapsed distance, in meters (Chainage) • 3-Dimensional Spatial Co-ordinates (GPS)

In addition to the machine based data parameters, the pavement-oriented digital video captured as part of the survey was used to carry out a rating of the road surface condition. The rating uses visual inspection to evaluate pavement surface conditions using a simplified rating scale of 1 to 10.

The RSP and SCRIM data were both chainage-referenced and geo-referenced for ease of post-processing. This ensures maximum compatibility with the MapRoad package (where the underlying data storage is chainage-based) as well as full compatibility with any GIS system including ArcGIS as the data is also accurately geo-referenced using GPS and Inertial Navigation System (INS) technology.

2.2 VISUAL CONDITION

A visual inspection of the pavement condition, identifying pavement distress types and severities is an invaluable aid in the evaluation of a pavement's performance. Manual condition inspection, where the pavement is examined by eye, and the distress quantities measured by hand is the most accurate and complete form of visual inspection. It also requires the least amount of additional equipment. However, there are situations where it is uneconomical to perform a detailed manual distress survey on pavement sections. This is particularly the case on lower class roads, where the available budget per kilometre is at a low level, and the costs of data collection per kilometre become excessively high as a percentage of the available budget.

Regional Roads Condition Study 2018 19

2.3 RATING PAVEMENT SURFACE CONDITION OF REGIONAL ROADS

The Pavement Surface Condition Index (PSCI) Manuals were developed in Ireland to provide a simple condition rating index for the evaluation and rating of the surface condition of Irish Regional and Local roads at network level. The manuals outline the different types of pavement defects for Irish roads, and provide a simplified 1 to 10 system to visually rate pavement surface condition. The manuals provide detailed descriptions of the distress types, how to link them to the 1 to 10 rating scale, and include high resolution colour photographs of the distress types and of road pavements in each of the 1 to 10 rating categories. The manuals provide a standardised approach to rate pavement condition and to link the pavement distress to specified treatment measures for Irish roads.

Figure 2.1: PSCI Rating 1 to 10

Regional Roads Condition Study 2018 20

The PSCI rating scale ranges from 10 for a pavement in excellent condition to 1 for a pavement in failed condition. For consistency of approach, the rating is assigned based on visible pavement defects only. The rating manual provides detailed descriptions on how to link the pavement defects to the 1 to 10 scale by identifying the distresses and the extent of those distresses visible on the pavement. There are three separate rating manuals for Rural Flexible, Urban Flexible and Urban Concrete roads.

2.4 INTERNATIONAL ROUGHNESS INDEX (IRI)

Road roughness has been defined as the variation in surface elevation that induces vibration in moving vehicles. In particular, the International Roughness Index (IRI) is a scale for roughness based on the response of a standardised motor vehicle to the road surface. The IRI simulates response to the surface profile, and also considers the effect of vehicle suspension. Roughness or ride quality is important as numerous studies have shown that there are strong correlations between motorists’ subjective ratings of ride quality and the ratings derived from measurement of IRI. In fact, the road user’s view of satisfactory or unsatisfactory road condition is primarily influenced by roughness or ride quality.

There are a number of different ways to measure ride quality, but the IRI has become the standard international scale. The IRI can be measured by an extensive range of equipment from rod and level through response-type meters to highly accurate laser-based profilometers.

The IRI is expressed in units of millimetres per metre, with low values indicating smooth roads, and high values indicating rough roads with poor ride quality. There is also significant correlation between IRI and the maximum speed at which a road user is comfortable. Table 2.1 shows a rough description of IRI scale translated into likely road defects and maximum speed with comfortable ride. The table is based on ASTM standard E1926-98, Standard Practice for Computing International Roughness Index of Roads from Longitudinal Profile Measurements.

IRI Value Comfortable Ride Speed Description (mm/m) 2 over 120 km/h Very Smooth 4 100 to 120 km/h Smooth 6 70 to 90 km/h Perceptible movement 8 50 to 60 km/h Some Swaying and Wheel Bounce

Regional Roads Condition Study 2018 21

10 40 to 50 km/h Significant Swaying 12 30 to 40 km/h Consistently Rough 14 < 30 km/h Very Rough

Table 2.1: IRI Scale

In the 2011 and 2018 Regional Road Surveys, the RSP laser profilometer system was used to measure the raw longitudinal profile and to calculate the IRI value. The RSP collects data at speeds up to 115km/hr. but is usually operated at typical vehicle speeds (c. 70km/hr), with continuous measurement. The entire data collection process is non- contact and the data from the surveys can be referenced to chainage or GPS.

The IRI was measured by the RSP laser profilometer system in both the left and right wheelpaths for each 10 metre interval surveyed. The average of the two wheelpath IRI readings, aggregated over 100 metre lengths, is calculated and reported over the full network, as this is considered a better measure of road surface roughness than the IRI for either individual wheel track.

In addition to IRI, the RSP longitudinal profile output is used to calculate 3 metre and 10 metre variance parameters at 10 metre intervals. This enhanced Longitudinal Profile Variance (LPV) required the collection of the short and medium wavelength features (3m and 10m variance) and the assessment of longitudinal profile in the nearside and offside wheel path at points separated by no more than 0.01m of longitudinal distance travelled.

2.5 RUT DEPTH

Rutting in the wheelpath is a structural distress induced by heavy vehicle traffic. Rutting is manifested as a permanent longitudinal deformation of the pavement creating channels in the wheelpaths. It is caused by the consolidation or lateral movement of material under repeated traffic loading, inadequate compaction of the pavement layers during construction or inadequate thickness of pavement layers.

Transverse profile measurements were recorded by the RSP machines for the entire Regional road network at a maximum longitudinal spacing of 1 metre in both the left and right wheelpaths. The basic RSP rut bar is 1.83m in width. Using a number of additional angled wing lasers on both ends of the basic rut bar, the total effective measurement width is increased to 3.2m.

Regional Roads Condition Study 2018 22

Rutting in the left wheelpath is generally more severe than in the right wheelpath and is typically reported internationally. Average rut values in millimetres (mm) were obtained for each 100 metre length from the measured transverse profile for the entire Regional road network. In addition to rut depth, the Shape Index and Edge Detection parameters on narrow pavements can also be calculated from the transverse profile data.

2.6 SURFACE TEXTURE

The macrotexture or surface texture of the pavement surface refers to the coarser texture defined by the shape of the individual coarse aggregate particles used in the surface course mix, and by the spaces between the individual aggregate chips. Macrotexture is the major influencing factor on frictional resistance at higher speeds (>50km/hr) and is particularly important in relation to wet conditions. The macrotexture provides the drainage channels for rainwater to escape to allow the vehicle tyre maintain greater contact with the pavement surface, in particular at high speeds. Macrotexture (texture depth) is expressed as mean profile depth (MPD) in millimetres.

The macrotexture profile of the Regional road network was measured to enable the MPD to be calculated at 1 metre intervals in accordance with ISO 13473-1:2004. The average MPD values were reported for each 100 metre length of Regional road.

2.7 SKIDDING RESISTANCE

The skidding resistance of a road pavement is a measure of the frictional resistance generated between the road surface and a tyre under standardised conditions. The microtexture of the road surface aggregate is the dominant factor in determining wet skidding resistance at lower speeds (<60km/h). Microtexture is primarily a property of the individual pieces of aggregate making up the road surface. The microtexture of the aggregate controls the contact between the tyre rubber and the pavement surface. From a skidding resistance viewpoint, the microtexture characteristics are measured to assess the degree of polishing and the ability of the aggregate to retain relatively rough microtexture under the abrasive action of tyre forces. Ultimately, it is the provision of adequate microtexture and macrotexture that is required for adequate surface friction resistance over the full spectrum of vehicle speeds.

The skidding resistance of the entire Regional road network was measured in the left hand wheel path using SCRIM. The output from the SCRIM is the sideway force coefficient (SFC) which is recorded at 10m intervals. It is a measure of the microtexture and low speed

Regional Roads Condition Study 2018 23 frictional resistance available on the pavement surface. The SFC values are adjusted to represent standardised conditions by applying speed and seasonal correction factors to the data recorded, resulting in a Characteristic SCRIM Coefficient (CSC). The CSC values were reported based on average values on each 100 metre length over the entire Regional network.

2.8 CONDITION CLASSES

In line with best practice internationally, five condition classes, namely Very Good, Good, Fair, Poor and Very Poor, have been defined for many of the technical parameters. Trend analysis showing percentages in each category, and changes in distribution over time, can be used to monitor overall network health, and impact of maintenance budgets on pavement condition. Table 2.2 below shows the Condition Class definitions for the Regional road network in 2018. The condition classes are used in Section 4 of this report to characterise the performance of local authority Regional roads.

Condition Class Very Good Good Fair Poor Very Poor IRI (mm/m) < 3 3 - 4 4 - 5 5 - 7 > 7 Rut (mm) < 6 6 - 9 9 - 15 15 - 20 > 20 CSC > 0.5 0.45 - 0.50 0.40 - 0.45 0.35 - 0.40 <= 0.35 LPV 3M < 2 2 - 4 4 - 7 7 - 10 > 10

Table 2.2: Condition Class Definitions, 2018

Regional Roads Condition Study 2018 24

SECTION 3: REPORTING OF NATIONAL RESULTS

3.1 GENERAL STATISTICS

The average values across the Regional road network from the 2018 survey are shown in Table 3.1 below. For comparison purposes, the average values from the 2011 survey are shown in Table 3.2 below.

Parameter Average Average IRI (mm/m) 4.0 Left Rut (mm) 9.1 MPD (mm) 1.4 CSC 0.5 PSCI 7.4 LPV 3m 3.8

Table 3.1: Average Performance Parameters, 2018

Parameter Aver- Average IRI (mm/m) age4.2 Left Rut (mm) 10.3 MPD (mm) 1.4 CSC 0.5 Visual Rating (PSCI) 7.2

Table 3.2: Average Performance Parameters, 2011

In general, it can be noted that the average values for each parameter are very similar in 2018 and 2011. For comparison purposes, the average IRI value on the Regional road network in the 2004 survey was 5.5 mm/m. The reduction in average network IRI value from 5.5 to 4.2 in 2011 was very significant, and showed a substantial improvement in ride quality on the Regional road network over the seven year period. It can be noted that the average IRI value shows a very small further reduction to 4.0 mm/m in 2018.

Average values are helpful for comparison purposes, but it is instructive to plot the cumulative frequency curves for each of the pavement parameters separately as this gives a better picture of the overall condition distribution of the network.

Regional Roads Condition Study 2018 25

Figure 3.1: Average IRI Cumulative Frequency Plot

It can be seen, for example, from Figure 3.1 that c. 20% of the Regional road network has an IRI value of 2.3 mm/m or less, c. 50% has an IRI value of 3.5 mm/m or less, and c. 90% of the network has an IRI value of 6.8 mm/m or less. The IRI values are quite evenly distributed across the network over the range shown, with the frequency curve being close to a straight line. While the average IRI value for the network is 4.0 mm/m, it can be seen from Figure 3.1 that 60% of the network has an IRI value of 4.0 mm/m or less.

Regional Roads Condition Study 2018 26

Figure 3.2: Left Rut Cumulative Frequency Plot

Figure 3.2 shows the Left Rut Cumulative Frequency plot. Unlike the IRI distribution curve, the left rut frequency curve is clearly curved, with just over 40% of the rut depth values measured less than 6 mm, and c. 10% of the values greater than 18 mm.

Figure 3.3: Mean Profile Depth (mm) Cumulative Frequency Plot

Regional Roads Condition Study 2018 27

Figure 3.3 shows a different distribution for the macrotexture parameter, MPD. There are c. 10% of the macrotexture measurements with a value of 0.7 mm or less. There is close to a uniform (straight line) distribution between 0.9 and 1.7 mm, with tails at the top and bottom of the distribution.

Figure 3.4: SCRIM CSC Cumulative Frequency Plot

Figure 3.4 shows the CSC distribution clearly has a long tail at the lower end, with relatively few values of 0.35 or less, and c. 12% of the 100 metre average values having a value of 0.40 or less. Most of the values measured range between 0.40 and 0.60, with another flattening out of the curve for values of greater than 0.6 CSC.

Regional Roads Condition Study 2018 28

Figure 3.5: PSCI Cumulative Frequency Plot

Figure 3.5 shows the PSCI Cumulative Frequency Plot, and there is clearly a different distribution to the other parameters. First, this is a discrete distribution, with only integer values between 1 and 10 used – all the machine parameters shown were continuous. It is clear that there is a very low percentage of 100 metre road sections on the Regional road network with Visual Rating values of 1, 2 or 3. The steepness of the curve between 7 and 9 shows that over 50% of the entire network had a Visual Rating of either 8 or 9 (generally in very good condition) based on a visual assessment of the Regional road network.

3.2 SUBGROUP OBSERVATIONS

Section 4 contains some detailed analysis of the results by local authority. However, it was also decided to group the Regional road network into five distinct subgroups to determine the extent of the differences in condition parameters across the subgroups. The subgroup definitions used were as follows:

Former National Roads These roads were reclassified as Regional roads over the course of the Inter-Urban Motorway developments

Regional Roads Condition Study 2018 29

Dublin All of the Regional roads from the four Dublin local authorities

Cities and Large Towns Cities were defined as Cork, Limerick, Galway and Waterford. Large towns were sourced from Ordinance Survey Ireland (OSI) polygons with Census Population > 10000.

Roads over Peat All Regional road segments overlying peat, as identified from a Geological Survey of Ireland (GSI) shapefile.

Remaining Regional Roads All other Regional roads not included in the four previous categories. These roads are predominantly rural in nature and will be referred to as Rural in the discussion that follows.

Total Length Per Local Authority (km) Total Former Dub- Remainder Local Authority Length City/Town Peat National lin (Rural) (km) CARLOW 185 24 0 10 0 152 CAVAN 400 3 0 0 28 369 CLARE 633 41 0 17 96 479 CORK 1368 52 0 0 102 1214 CORK CITY 37 0 0 37 0 0 DUBLIN CITY 200 0 200 0 0 0 DUN LAOGHAIRE RATHDOWN 103 0 103 0 0 0 DONEGAL 782 16 0 9 332 426 FINGAL 254 0 254 7 0 0 GALWAY CITY 37 2 0 37 0 0 GALWAY 894 118 0 0 180 595 KERRY 529 9 0 17 97 406 KILDARE 493 131 0 35 36 292 KILKENNY 421 86 0 0 4 330 LAOIS 348 61 0 0 28 259 LEITRIM 332 0 0 0 63 269 LIMERICK 531 42 0 32 18 439 LONGFORD 151 0 0 0 59 93 LOUTH 274 76 0 44 2 152 MAYO 623 7 0 12 200 404 MEATH 575 92 0 13 12 458 MONAGHAN 297 0 0 0 33 264 OFFALY 392 44 0 14 106 227 ROSCOMMON 375 20 0 0 70 285 SLIGO 235 4 0 10 70 151 SOUTH DUBLIN 116 0 116 0 1 0 TIPPERARY 894 121 0 18 32 724

Regional Roads Condition Study 2018 30

WATERFORD 425 14 0 40 5 366 WESTMEATH 313 64 0 9 35 205 WEXFORD 475 21 0 19 0 436 WICKLOW 460 42 0 26 32 361 Totals 13150 1087 673 405 1638 9356

Table 3.3: Subgroup Lengths by Local Authority

It can be seen from Table 3.3 that there are c. 1100 km of Former Nationals, close to 700 km of Dublin Regional roads, c. 400 km of other City/Large Town Regional roads, over 1600 km of Regional roads over Peat and c. 9,350 km of Rural Regional roads. The distribution of the subgroups varies widely across local authorities and contributes to some of the variability in average condition parameters.

Figure 3.6: IRI Distributions by Subgroup

It can be seen in Figure 3.6 that there is considerable variability in condition distributions across the subgroups when examining the IRI parameter. The Former Nationals show by far the best distribution with most of the subgroup in the best two classes (dark green and light green). Dublin and the Cities/Large Towns groupings are broadly similar, and clearly better than the Rural Regional roads. The Regional roads over Peat clearly show the poorest ride quality with a much lower percentage in the two best classes, and a much higher percentage in the worst (red) class.

Regional Roads Condition Study 2018 31

Figure 3.7: Rut Depth Distributions by Subgroup

It can be seen in Figure 3.7 that the Former Nationals and the Dublin subgroups are quite similar to one another, and considerably better than the other three subgroups. Regional roads over Peat again shows the poorest structural condition on average (as measured by rut depth) but the distribution is not as markedly different to the City/Large Towns and Rural Regional roads groupings as was the case with IRI.

Figure 3.8: CSC Distributions by Subgroup

Regional Roads Condition Study 2018 32

Figure 3.8 shows the distributions of CSC (skid resistance) across the subgroups. On this parameter, Roads over Peat has clearly the best distribution, with over 90% in the best two classes. Cities/Large Towns and Rural Regional roads again show very similar distributions – this was previously noted in the Rut Depth distributions. Dublin and Former Nationals have clearly much higher percentages in the bottom two CSC classes. This may reflect different surfacing materials and also higher traffic levels leading to polishing of the surface aggregates.

Figure 3.9: PSCI Distributions by Subgroup

Finally Figure 3.9 shows the PSCI (visual condition) parameter distributions across the five subgroups. This figure shows by far the most similar distribution pattern across all five subgroups. The Former Nationals have the highest percentage in the best (9-10) class, but the other four subgroups are very similar to each other across all four PSCI condition classes.

Regional Roads Condition Study 2018 33

SECTION 4: RESULTS BY LOCAL AUTHORITY 2018

4.1 GENERAL STATISTICS BY COUNTY

Table 4.1 below shows the average values of the machine and Visual Rating (PSCI) parameters in each local authority.

Local Authority IRI RUT CSC MPD PSCI LPV 3m CARLOW 3.3 9.1 0.41 1.4 7.4 2.2 CAVAN 3.8 9.6 0.50 1.3 7.3 3.2 CLARE 4.5 10.4 0.51 1.5 7.4 4.2 CORK 4.7 10.9 0.51 1.3 7.1 5.0 CORK CITY 4.5 4.2 0.50 1.3 6.5 4.6 DUBLIN CITY 4.1 3.6 0.43 1.1 7.0 4.1 DUN LAOIGHRE RAT. 3.8 4.8 0.42 1.3 7.4 3.4 DONEGAL 5.0 11.0 0.58 1.4 7.5 6.5 FINGAL 3.4 5.3 0.46 1.3 7.6 2.9 GALWAY CITY 3.6 4.0 0.41 1.3 8.0 3.5 GALWAY 4.0 9.6 0.54 1.4 7.6 3.8 KERRY 4.0 9.5 0.51 1.3 7.5 3.0 KILDARE 3.1 5.5 0.44 1.4 7.8 2.5 KILKENNY 3.5 8.9 0.45 1.4 7.4 2.3 LAOIS 3.7 8.2 0.42 1.4 7.1 2.8 LEITRIM 3.4 9.0 0.60 1.3 8.1 2.9 LIMERICK 3.8 9.0 0.47 1.6 7.3 3.0 LONGFORD 3.3 8.2 0.51 1.4 8.2 2.5 LOUTH 3.0 6.3 0.47 1.4 7.7 2.6 MAYO 4.8 11.2 0.53 1.5 7.5 6.0 MEATH 3.5 7.4 0.45 1.4 7.6 2.7 MONAGHAN 3.2 6.9 0.47 1.2 7.4 1.9 OFFALY 4.3 9.9 0.47 1.4 6.6 4.1 ROSCOMMON 3.0 8.4 0.56 1.4 8.1 2.3 SLIGO 3.8 10.6 0.57 1.4 7.6 3.8 STH DUBLIN 3.3 4.4 0.45 1.4 8.1 2.6 TIPPERARY 4.4 11.0 0.46 1.5 7.1 4.1 WATERFORD 4.1 7.6 0.51 1.3 7.2 3.6 WESTMEATH 3.0 7.0 0.49 1.3 8.1 2.2 WEXFORD 4.0 9.7 0.41 1.3 6.8 3.3 WICKLOW 4.3 10.0 0.47 1.6 7.1 4.4

Table 4.1: Condition Parameters – Average Values 2018

It can be seen from the tables that there are significant variations in average road condition as measured by the various parameters across the local authorities. There are a number of factors that may influence the average value including underlying subgrade

Regional Roads Condition Study 2018 34 condition, pavement layer thicknesses, quality of material present and maintenance practices. In addition, some counties will show better average results due to the reclassification of former National routes to Regional routes as the Motorway network expanded in the past few years.

IRI Class (mm/m) Local Authority Very Good Good Fair Poor Very Poor CARLOW 58% 19% 9% 10% 4% CAVAN 35% 27% 18% 16% 4% CLARE 27% 18% 18% 26% 11% CORK 21% 21% 21% 23% 14% CORK CITY 18% 29% 18% 26% 9% DUBLIN CITY 30% 26% 19% 18% 8% DUN LAOGHAIRE RATHDOWN 33% 31% 17% 15% 5% DONEGAL 29% 17% 14% 20% 20% FINGAL 48% 25% 14% 9% 4% GALWAY CITY 39% 32% 15% 10% 4% GALWAY 36% 23% 15% 18% 7% KERRY 28% 28% 23% 16% 5% KILDARE 62% 19% 8% 7% 3% KILKENNY 46% 25% 14% 14% 2% LAOIS 37% 27% 19% 13% 4% LEITRIM 49% 24% 14% 10% 3% LIMERICK 33% 29% 20% 14% 3% LONGFORD 51% 26% 13% 8% 2% LOUTH 63% 19% 8% 7% 3% MAYO 29% 20% 14% 19% 18% MEATH 50% 20% 12% 13% 5% MONAGHAN 54% 25% 11% 8% 2% OFFALY 32% 18% 15% 25% 11% ROSCOMMON 66% 16% 8% 6% 3% SLIGO 40% 26% 15% 12% 7% STH DUBLIN 52% 25% 12% 8% 3% TIPPERARY 26% 20% 21% 23% 9% WATERFORD 46% 14% 8% 20% 13% WESTMEATH 62% 20% 8% 7% 2% WEXFORD 37% 19% 17% 19% 8% WICKLOW 34% 19% 15% 19% 13%

Table 4.2: IRI – Condition Classes by Local Authority 2018

Table 4.2 shows the distribution of IRI values across the 5 defined pavement classes for each local authority. Lower values of IRI indicate better ride quality. The IRI classes range from Very Good (< 3 mm/m) to Very Poor (> 7 mm/m) and are detailed in Table 2.2 earlier in this report.

Regional Roads Condition Study 2018 35

Figure 4.1 shows a colour graded map of the Percentage of the Regional road network in each local authority in Fair or Better condition (IRI of 5 mm/m or less). In this Figure, and in all of the colour graded maps in this report, lighter shades indicate a higher percentage in Fair or Better condition. The local authority values range from 60% to 90% in Fair or Better condition.

Figure 4.1: IRI (% Fair or Better) by Local Authority, 2018

Regional Roads Condition Study 2018 36

Table 4.3 shows the distribution of Rut Depth values across the 5 defined pavement classes for each local authority. Lower values of Rut Depth indicate better structural condition. The Rut Classes range from Very Good (< 6 mm) to Very Poor ( > 20 mm).

Rut Class (mm) Local Authority Very Good Good Fair Poor Very Poor CARLOW 40% 16% 26% 13% 6% CAVAN 37% 16% 26% 13% 7% CLARE 32% 14% 28% 17% 9% CORK 28% 15% 30% 17% 10% CORK CITY 84% 10% 5% 1% 0% DUBLIN CITY 88% 8% 3% 1% 0% DUN LAOGHAIRE RATHDOWN. 75% 10% 12% 3% 0% DONEGAL 32% 13% 25% 17% 13% FINGAL 70% 13% 13% 3% 1% GALWAY CITY 84% 12% 4% 1% 0% GALWAY 38% 16% 25% 14% 8% KERRY 35% 16% 28% 14% 7% KILDARE 71% 11% 11% 5% 2% KILKENNY 42% 15% 24% 13% 6% LAOIS 47% 16% 21% 11% 5% LEITRIM 40% 16% 25% 13% 6% LIMERICK 39% 17% 26% 12% 6% LONGFORD 45% 18% 23% 10% 4% LOUTH 64% 13% 15% 5% 3% MAYO 31% 13% 25% 17% 14% MEATH 56% 12% 17% 9% 5% MONAGHAN 55% 17% 19% 6% 2% OFFALY 38% 15% 23% 15% 10% ROSCOMMON 44% 15% 25% 10% 5% SLIGO 31% 15% 29% 15% 10% STH DUBLIN 79% 10% 9% 1% 0% TIPPERARY 31% 13% 26% 17% 12% WATERFORD 53% 13% 19% 10% 5% WESTMEATH 57% 14% 18% 8% 4% WEXFORD 38% 14% 26% 14% 8% WICKLOW 36% 14% 25% 16% 9%

Table 4.3: Rut Depth – Condition Classes by Local Authority 2018

Regional Roads Condition Study 2018 37

Figure 4.2 shows a colour graded map of the Percentage of the Regional road network in each local authority in Fair or Better condition (Rut Depth of 15 mm or less). The local authority values range from 70% to 99% in Fair or Better condition.

Figure 4.2: Rut Depth (% Fair or Better) by Local Authority, 2018

Regional Roads Condition Study 2018 38

Table 4.4 shows the distribution of PSCI ratings across the 4 defined pavement classes for each local authority. Higher values of PSCI indicate better visual pavement condition.

PSCI Class Local Authority 9 and 10 7 and 8 5 and 6 1 to 4 CARLOW 29% 44% 22% 5% CAVAN 29% 38% 25% 8% CLARE 34% 30% 28% 8% CORK 26% 33% 29% 11% CORK CITY 11% 27% 44% 18% DUBLIN CITY 31% 21% 37% 11% DUN LAOGHAIRE RATHDOWN. 35% 32% 25% 9% DONEGAL 35% 30% 25% 10% FINGAL 47% 19% 23% 12% GALWAY CITY 57% 11% 32% 0% GALWAY 41% 27% 26% 6% KERRY 37% 29% 30% 5% KILDARE 42% 33% 18% 7% KILKENNY 29% 42% 25% 5% LAOIS 26% 37% 29% 9% LEITRIM 55% 25% 16% 4% LIMERICK 26% 36% 29% 9% LONGFORD 44% 42% 12% 2% LOUTH 44% 28% 21% 7% MAYO 43% 21% 31% 5% MEATH 44% 26% 22% 8% MONAGHAN 37% 32% 23% 9% OFFALY 20% 29% 31% 20% ROSCOMMON 59% 20% 17% 4% SLIGO 45% 24% 23% 8% STH DUBLIN 47% 35% 17% 1% TIPPERARY 27% 31% 33% 9% WATERFORD 26% 38% 28% 8% WESTMEATH 48% 38% 12% 2% WEXFORD 23% 30% 34% 13% WICKLOW 22% 43% 25% 10%

Table 4.4: PSCI – Condition Classes by Local Authority 2018

Regional Roads Condition Study 2018 39

Figure 4.3 shows a colour graded map of the Percentage of the Regional road network in each local authority with a PSCI rating of 5 or greater. This equates roughly with the Fair or Better approach used for the other machine parameters.

Figure 4.3: PSCI (% with Rating of 5 or Better) by Local Authority, 2018

Regional Roads Condition Study 2018 40

Table 4.5 shows the distribution of SCRIM CSC values across the 5 defined pavement classes for each local authority. The classes range from Very Good (CSC of > 0.50) to Very Poor (

CSC Class Local Authority Very Good Good Fair Poor Very Poor CARLOW 8% 17% 31% 21% 23% CAVAN 48% 27% 18% 6% 1% CLARE 56% 23% 13% 5% 2% CORK 58% 23% 11% 4% 3% CORK CITY 50% 34% 12% 3% 1% DUBLIN CITY 9% 21% 32% 27% 11% DUN LAOGHAIRE RATHDOWN 11% 16% 27% 29% 18% DONEGAL 85% 10% 4% 1% 0% FINGAL 26% 27% 25% 17% 6% GALWAY CITY 12% 13% 22% 31% 22% GALWAY 72% 14% 8% 4% 2% KERRY 58% 24% 10% 6% 3% KILDARE 19% 23% 27% 19% 13% KILKENNY 24% 26% 25% 14% 11% LAOIS 21% 16% 18% 18% 28% LEITRIM 93% 5% 2% 0% 0% LIMERICK 33% 25% 22% 13% 8% LONGFORD 65% 25% 8% 2% 1% LOUTH 31% 30% 26% 11% 2% MAYO 70% 18% 7% 3% 2% MEATH 22% 26% 32% 15% 5% MONAGHAN 32% 31% 23% 9% 5% OFFALY 32% 32% 20% 9% 7% ROSCOMMON 84% 11% 4% 1% 0% SLIGO 79% 13% 5% 2% 1% STH DUBLIN 22% 17% 25% 24% 12% TIPPERARY 32% 27% 19% 11% 11% WATERFORD 54% 25% 13% 6% 3% WESTMEATH 43% 32% 19% 5% 1% WEXFORD 14% 17% 27% 20% 23% WICKLOW 33% 24% 23% 14% 6%

Table 4.5: SCRIM CSC – Condition Classes by Local Authority 2018

Regional Roads Condition Study 2018 41

Figure 4.4 shows a colour graded map of the Percentage of the Regional road network in each local authority in Fair or Better condition (CSC of 0.4 or more). The local authority values range from 40% to 100% in Fair or Better condition. The values are likely to be significantly influenced by the type of surfacing material available in the area, traffic volumes and by the age and average resurfacing cycle length in the local authority. There is a clear difference between Eastern and Western local authorities, with the Western local authorities showing significantly higher values in Fair or Better condition.

Figure 4.4: CSC (% Fair or Better) by Local Authority, 2018

Regional Roads Condition Study 2018 42

Figure 4.5 shows a national distribution of Mean Profile Depth (MPD) results, an indicator of the skid resistance available from the pavement macrotexture. Unlike the other parameters discussed in this chapter, neither Very Low nor Very High values of MPD are desirable. Very Low values of MPD (< 0.6 mm) indicate relatively poor skidding resistance. Very High values of MPD typically indicate a loss of chippings from the pavement surface.

Figure 4.5 shows the Percentage of roads in each local authority with MPD values of 0.6 mm or less. The local authority values mapped range from close to 0% up to 10%. The average values are likely to be significantly influenced by the percentage length of surface dressing used within each local authority on the Regional network, as surface dressing tends to yield significantly higher average MPD readings compared with most hot mix bituminous materials.

Figure 4.5: Macrotexture (% < 0.6 mm) by Local Authority, 2018

Regional Roads Condition Study 2018 43

SECTION 5: REMEDIAL WORKS CATEGORIES

The primary outturn of the 2018 Regional Road Pavement Condition Study is the length, average width and area of Regional road in each county requiring various types of remedial works as defined in the consultancy brief. Figure 5.1 shows the Treatment/Works Type Categories as set out in the DTTAS Pavement Survey Standard for Regional and Local Roads (Feb. 2018).

5.1 DESCRIPTION OF REMEDIAL WORKS CATEGORIES

Figure 5.1: Treatment/Works Type Categories

The remedial works categories specified in the consultancy brief were:

• Routine Maintenance • Restoration of Skid Resistance • Surface Restoration, • Structural Rehabilitation • Road Reconstruction

Regional Roads Condition Study 2018 44

Surface Restoration was defined to include improvement of transverse and longitudinal drainage, pothole patching, restoration of road width and strengthening of road edges as well as localised surface dressing of the repaired areas. Road Reconstruction was defined to include excavation and reconstruction of existing road pavement. Structural Rehabilitation includes overlaying or inlaying of existing road pavements with bound or unbound materials to increase the structural capacity of the road section. Restoration of Skid Resistance covers the application of a surface treatment to reseal the road and restore adequate skid resistance.

Routine Maintenance was defined to include road section lengths not requiring any of the four remedial work types defined above. Road sections in this category would be in very good current condition.

5.2 ALLOCATION OF SAMPLE UNITS INTO MAINTENANCE CATEGORIES – 2018 METHODOLOGY

In the 2018 survey, there are a number of pavement parameters collected that can be used to determine the allocation of the Regional road network into the 5 maintenance categories. On the safety side, both SCRIM (CSC) and macrotexture (MPD) were measured, giving better measures of the requirement for Restoration of Skid Resistance than a visual survey alone can provide. Longitudinal profile (IRI) and transverse profile (rut depth) were measured directly in the 2018 survey by the RSP machine – these parameters give a measure of distress types such as rutting, depressions and deformation that are the most difficult to consistently identify visually from a video survey.

The 100m sample units for each Regional road are assigned to the remedial works categories based on the machine data parameters of safety (SCRIM and texture), ride quality (IRI and variance parameters) and structural (rutting) values.

The PSCI rating scheme was developed specifically with the aim of directly mapping the PSCI rating to the desired maintenance categories. Thus, PSCI of 1 to 2 maps to the Road Reconstruction category, PSCI rating of 3 and 4 maps to the Structural Rehabilitation category. PSCI rating of 5 and 6 maps to the Surface Restoration category, PSCI rating of 7 and 8 maps to the Restoration of Skidding Resistance category, and PSCI rating of 9 and 10 maps to the Routine Maintenance category. A number of combinations of parameters can be considered in this light.

Regional Roads Condition Study 2018 45

Every 100 metre road segment is examined first to determine if it meets any of the criteria for Road Reconstruction. If the segment meets one of the criteria, it is assigned to Road Reconstruction and is excluded from consideration for any other category.

If none of the criteria are met, the road segment parameters are successively examined to determine if they meet the criteria for Structural Rehabilitation, Surface Restoration or Restoration of Skid Resistance. As before, if the segment meets one of the criteria, it is assigned to that maintenance category and is excluded from consideration for any other maintenance category.

If the segment does not meet any of the criteria for these 4 maintenance categories, it is assigned to the Routine Maintenance category.

This allocation mechanism applies to all Regional road segments except for those segments with a road width of less than 4 metres. This is a very small percentage of the total, with just over 60 kilometres out of 13,150 kilometres falling into this group. For these very narrow roads, where road width rather than pavement condition will govern the operating speed of the road used, the PSCI rating only is used to determine the maintenance category. For all other Regional road segments, the criteria in sections 5.2.1 to 5.2.5 below apply.

5.2.1 Road Reconstruction

The criteria for inclusion in the Road Reconstruction category are as follows:

IRI > 12 mm/m

Left Wheelpath Rut Depth > 40 mm

PSCI Rating of 1 or 2

Effectively, this category captures sections with extremely poor ride quality, very significant structural weakness or extremely poor visual condition.

Regional Roads Condition Study 2018 46

5.2.2 Structural Rehabilitation

The criteria for inclusion in the Structural Rehabilitation category are as follows:

IRI between 7 and 12 mm/m

Left Wheelpath Rut Depth between 20 and 40 mm

PSCI Rating of 3 or 4

This category captures sections in need of structural strengthening.

5.2.3 Surface Restoration

The criteria for inclusion in the Surface Restoration category are as follows:

PSCI Rating of 5 or 6

IRI between 6 and 7 mm/m AND PSCI Rating of 7 to 10

The PSCI categories of 5 and 6 were designed to map to the Surface Restoration category. In addition, 100 metre stretches with better Visual Rating, but relatively poor ride quality, were included in the second criterion shown.

5.2.4 Restoration of Skid Resistance

The criteria for inclusion in the Surface Restoration category are as follows:

PSCI Rating of 7 or 8

PSCI Rating of 9 or 10 AND CSC of 0.35 or less

Regional Roads Condition Study 2018 47

PSCI Rating of 9 or 10 AND MPD of 0.7 mm or less

The PSCI categories of 7 and 8 were designed to map to the Restoration of Skid Resistance category.

In addition, 100 metre stretches with better Visual Rating (9 or 10), but relatively poor skid resistance as indicated by SCRIM value (CSC) or MPD (macrotexture) were included in the second and third criteria above.

5.2.5 Routine Maintenance

All other 100 metre segments not already allocated to one of the other four maintenance categories are included in this category. By a process of elimination, 100 metre stretches in this category have very good visual rating (9 or 10), IRI values of less than 6 mm/m, rut depth values of less than 20 mm, CSC values greater than 0.35 and MPD values greater than 0.7 mm.

Regional Roads Condition Study 2018 48

SECTION 6: REMEDIAL WORKS REQUIREMENTS

6.1 NATIONAL REQUIREMENTS

Chapter 5 of this report laid out the basis for assignment of road sample units to the different remedial works categories. There are almost 131,000 sample units, each 100 metres in length, on the Regional road network.

On the basis of these remedial works category definitions, Table 6.1 and Figure 6.1 outline the percentage length of Regional roads nationally in each of the 5 maintenance categories when the 100 metre sample units are assigned to the categories:

Per- Treatment Category Length (km) cent Road Reconstruction 60 0.5% Structural Overlay 2418 18.6% Surface Restoration 2952 22.7% Skid Resistance 3663 28.2% Routine Maintenance 3887 29.9%

Table 6.1: Maintenance Categories - % in 2018

Figure 6.1: 2018 Remedial Works Categories

Regional Roads Condition Study 2018 49

The results are not directly comparable with the 2011 out-turn as there are five maintenance categories considered in 2018 compared with four categories in 2011. In addition, there have been some minor adjustments to the individual criteria used to allocate segments to maintenance categories in 2018.

6.2 REMEDIAL REQUIREMENTS BY LOCAL AUTHORITY

Table 6.2 shows the percentage of Regional road length in each of the 5 remedial works categories for all of the local authorities based on the 2018 survey results.

ROAD STRUCT SURFACE SKID ROUTINE Local Authority RECON. OVERL. REST. RESIST. MAINT. CARLOW 0.1 12.6 18.7 45.9 22.7 CAVAN 0.1 16.6 23.3 35.6 24.5 CLARE 0.3 21.5 24.5 23.9 29.8 CORK 0.5 26.4 24.4 27.2 21.5 CORK CITY 0.6 22.6 40.0 26.3 10.6 DUBLIN CITY 0.1 16.6 35.7 21.9 25.6 DUN LAOGHAIRE RATHDOWN. 0.1 12.9 24.5 32.3 30.2 DONEGAL 2.4 26.9 19.2 23.7 27.8 FINGAL 0.1 14.7 22.6 19.8 42.8 GALWAY CITY 1.0 3.5 32.6 16.0 46.9 GALWAY 0.5 16.8 23.3 23.5 36.0 KERRY 0.1 13.0 27.3 25.9 33.7 KILDARE 0.3 10.9 18.2 34.9 35.7 KILKENNY 0.1 11.5 23.3 40.4 24.7 LAOIS 0.1 14.4 26.4 38.1 20.9 LEITRIM 0.2 10.7 16.2 25.7 47.2 LIMERICK 0.1 15.8 27.2 34.3 22.7 LONGFORD 0.0 7.1 12.5 40.5 40.0 LOUTH 0.1 11.4 19.6 28.3 40.6 MAYO 1.8 25.2 21.0 17.2 34.8 MEATH 0.1 14.0 19.6 26.0 40.2 MONAGHAN 0.1 11.2 22.5 32.6 33.5 OFFALY 0.4 29.9 26.4 25.5 17.9 ROSCOMMON 0.1 9.8 14.8 19.1 56.1 SLIGO 0.2 20.4 18.1 22.2 39.1 STH DUBLIN 0.1 4.2 17.3 37.6 40.8 TIPPERARY 0.3 23.6 27.0 25.7 23.5 WATERFORD 0.1 20.2 22.6 33.8 23.3 WESTMEATH 0.1 6.7 11.5 37.4 44.3 WEXFORD 0.4 22.8 28.2 29.8 18.8 WICKLOW 0.6 24.2 23.3 34.1 17.9

Regional Roads Condition Study 2018 50

Table 6.2: Percentage length of Regional Roads in each Remedial Work Category

Figure 6.2: 2018 Structural Rehabilitation Requirements

For comparison purposes, the categories of Road Reconstruction and Structural Overlay were combined for each local authority and plotted using a colour graded map in Figure 6.2 above. As before, darker shades indicate higher quantities of required Structural Rehabilitation. There is a large range across the local authorities, with rural authorities showing a range from 7% to 30%.

Regional Roads Condition Study 2018 51