Non National (Regional & Local) Road Needs Study

Pavement Condition Study on Non-National Roads (Regional & Local Roads)

The Department of the Environment, Heritage and Local Government (DEHLG) commissioned RPS MCOS Ltd. and PMS Pavement Management Services Ltd to carry out a pavement condition study on the Non-National roads. The main objectives of the 2004 Pavement Condition Study, as set out in Schedule 4 of the Request for Proposals document are:

• To establish, by county and nationally, the lengths and areas of various categories of non-national roads requiring remedial works, and
• To review existing pavement management systems and recommend a system suitable for use on the non-national road network

A 2001 National Roads Authority study on vehicle-kilometres of travel in Ireland indicated that the Non-National road network carries 59% of all car travel, 56% of all LGV travel, and 43% of all HGV travel, clearly showing the importance of the Non-National road network in the Irish context.

There has been a very large growth in Heavy Goods Vehicles (HGV) numbers since 1995. The HGV numbers have grown by 6% per annum over this period. Taking Light Goods Vehicles (LGV) and HGV together, there was an annual growth of 7.6% over this period, exactly the same as the average GDP growth rate of 7.6% per annum from 1996 to 2003.

The increase in HGV numbers has been predominantly in the provision of much larger and more damaging HGV.  The combination of growth in numbers and damaging power has dramatically increased the structural loading on the network since 1996.

Overall, it can be concluded that the economic boom in Ireland since the last condition survey in 1996 has fundamentally changed the loading regime on the Non-National road network, with much higher and more frequent loadings by heavier vehicles being the norm in 2004.

A total of over 8,000 kilometres of Non-National roads were surveyed in 2004. The Engineering Area was chosen as the base unit for sampling, with roads in all 4 road classes (Regional, Local Primary, Local Secondary, Local Tertiary) selected for survey in every Engineering Area in the country.

A data collection methodology to maximise the speed of data collection in the field was developed. The entire data collection effort was completed using 4 video vans over a 15 week period in early 2004.

The methodology relies on high-definition digital video to capture the road surface condition. The video is subsequently post-processed in the office to produce condition information on each 100 metre sample unit.

The condition measurement produces a Pavement Condition Index (PCI). A new pavement (theoretically distress-free) has a PCI of 100. For each distress measured, there are deduct values depending upon the nature of the distress, its severity and quantity. The deduct values are summed, adjusted to take into account the total number of distresses identified, and then subtracted from 100 to give the PCI index for the pavement.

In addition, a further condition parameter, the ride quality of each pavement section, was recorded in the 2004 survey. This parameter is measured in International Roughness Index (IRI) units. The IRI is important as the road users view of satisfactory or unsatisfactory road condition is primarily influenced by roughness or ride quality.

The remedial works categories are Surface Restoration, Road Reconstruction and Restoration of Skid Resistance. Surface Restoration was defined to include improvement of 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 reconstruction of existing road pavements, overlaying of existing road pavements with bound or unbound materials surface dressed, and raising of road levels to prevent flooding with provision of drainage. Restoration of Skid Resistance covers the application of a surface treatment to restore adequate skid resistance. A fourth category, Routine Maintenance, was defined by the consultants to include road section lengths not requiring any of the three remedial work types defined  above. Road sections in this category would be in very good existing condition.

The initial assignment of each surveyed sample unit to one of the remedial works categories is primarily based on the PCI value. This is consistent with the approach taken in the last major national study of Non-National road conditions in 1996.

In the 2004 study, the ride quality data is also used to modify the results derived from the visual survey. In particular, road segments with poor or very poor ride quality characteristics are moved into the Road Reconstruction category. Only the Road Reconstruction activities can restore the ride quality of the pavement section to an acceptable level.

There is a clear downward progression by road class in average PCI, from 68 on Regional (R) roads down to 50 on Local Tertiary (LT) roads. The IRI ride quality average values show a similar trend. The smoothest roads (lowest IRI) are on the R roads with an average value of 5.3 m/km, while the LT roads show the highest average value at 11.8 m/km, more than double the value for the Regional roads. The differences in PCI and IRI by road class are large, and reflect clearly different conditions nationally by road class.

When individual distress patterns are examined, it is clear that Ravelling occurs much more frequently than other distresses. Rutting is the second most frequently occurring distress. This is significant as Rutting is a structural distress, carrying a relatively high deduct value, and having implications for the maintenance requirements of the section.  Patching and Bleeding have a similar rate of occurrence, significantly higher than Edge Breakup. Potholes, Alligator Cracking and Depressions have a relatively low rate of occurrence, with Road Disintegration and Other Cracking having a very low rate of occurrence.

When the 1996 and 2004 surveys are compared, the main trends are:

There has been a substantial increase in the occurrence of Ravelling in 2004 compared to 1996. The percentage occurrence of Bleeding is lower in 2004. These differences may reflect the difference in the time of year when the survey was carried out.

There has also been a substantial increase in the occurrence of Rutting between 1996 and 2004. This reflects the much larger traffic volumes, and in particular the much heavier and wider commercial vehicles using the road network over the past 8 years. There has been a very significant increase overall in commercial traffic volumes in line with economic growth.

Without the strengthening programme that was put in place since the mid 1990s, the rate of occurrence of all structural distresses in 2004 would have been much higher than in 1996. In fact, the rate of occurrence of Potholes and Road Disintegration has effectively halved over the period from 1996 to 2004, while the rate of occurrence of Patching is also substantially reduced. This reflects the significant investment in the road network with priority obviously being applied to road sections with surface breaks.

Overall, the distress comparisons show that the Non-National network is very significantly better in 2004 in reducing the incidences of surface breaks (Potholes and Road Disintegration) that produce high levels of road user dissatisfaction. This reduction has occurred in the context of much heavier and more frequent loadings on all road classes of the Non-National network. However, this greater loading has increased the amount of rutting on the network substantially, and this has significant implications for the structural maintenance budgets required going forward.

Pavement Management System Review Report

The review of Pavement Management Systems was carried out as part of project commissioned by the Department of the Environment, Heritage and Local Government to carry out a Pavement Condition Study of the Non-National Road Network in Ireland.

This report describes the results of the review of Pavement Management Systems. It includes details of the determination of needs and requirements, evaluation of available Pavement Management Systems, and conclusions and recommendations arising from the study.

User needs and requirements were established through a series of questionnaires, circulated to local authorities in Ireland, followed by interviews with selected authorities, both in Ireland and in the United Kingdom. Information gathered during this process, together with information on good PMS practice, was used to develop a set of PMS System Requirements that could be used to evaluate the suitability of available pavement management systems. In addition, a number of factors and issues were identified that would affect any implementation process.

A total of ten commercially available pavement management systems were evaluated against these requirements to determine which best satisfied the needs. The conclusion of this evaluation was that four commercially available systems (Exor Highways, Insight Pavement Manager, dTIMS and Confirm Pavement Manager) provided excellent features and functionality, with the required degree of openness to allow for customisation to suit Irish conditions. The initial cost of a typical commercial system is around €45,000 per authority.

A possible alternative to purchasing a commercial PMS is to develop an in-house system that is designed to provide the functionality required by road authorities in Ireland. This alternative was explored through evaluation of MapRoad, an existing GIS-enabled Road Management Information System, provided by the Local Government Computer Services Board and currently installed in most road authorities. This evaluation concluded that the present system could be relatively easily modified and improved within a year to provide the majority of the PMS functionality that is required, with further improvements following thereafter. The total cost of this enhancement is estimated at €500,000 or around €14,700 per local authority.

The recommendations arising from the study are:

1.    That the enhancement of MapRoad be adopted as part of a structured implementation process, in cognisance of the following factors:

" The need for an incremental, structured approach towards implementation

" The timescale required to implement PMS in Ireland

" The need to properly define data and processing requirements before system implementation

" The availability of a strong, dedicated, system development team to enhance MapRoad

" The anticipated reasonable cost of MapRoad system development compared to commercial systems

2.    That the structured implementation process take into account, inter alia, the implementation factors identified in the report, to ensure the initiative is a success.

3.    That external expert assistance should be brought in to help guide the implementation process. 

4.    That a steering group be instituted to oversee and coordinate the implementation process, with working groups as needed to focus on specific data and processing issues. 

5.    That the implementation process should include a review of network definition rules and should ensure that the network definition system can accommodate all the anticipated data needs of the road authorities. 

6.    That the implementation process should also allow for raising the profile and awareness of PMS within local authorities, as this will pay dividends in obtaining participation in the process and in ultimately using the system.