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Enhanced Road Condition Project

Part 2 Condition Performance Report 2009

Enhanced Road Condition Project: Final Performance Report Part 2: Condition Performance Report October 2009

Department of Transport and Main Roads

Prepared by Danny Pedri Title Senior Engineer Branch Road Asset Management Division Road and Delivery Performance Location 477 Boundary St, Spring Hill, 4000 Version no. 1.2 Revision date 27 October 2009 Status Final DMS ref. no.



Table of contents

1 Executive summary.......................................................................................... 4

2 Introduction....................................................................................................... 7

2.1. Objectives ......................................................................................................................... 7

2.2. Background....................................................................................................................... 7

2.3. Location and Program of Works....................................................................................... 8

2.4. Road Environment .......................................................................................................... 11

3 Project Feasibility Studies ............................................................................. 12

3.1. DTMR Feasibility Studies ............................................................................................... 12

3.1.1. Base Case Study ..........................................................................................................12

3.1.2. Base Case results.........................................................................................................13

3.1.3. Base Case Alternatives Study ......................................................................................13

3.1.4. Base Case Alternative Results .....................................................................................14

3.2. Contractor Feasibility Studies......................................................................................... 16

3.2.1. BMC Consortium Feasibility Study ...............................................................................16

3.2.2. Revised As-constructed Feasibility Study ....................................................................17

4 Condition Feasibility Criteria Outcome ........................................................ 19

4.1. Ride Quality .................................................................................................................... 19

4.2. Structural Performance................................................................................................... 19

4.3. Condition Quality Index .................................................................................................. 20

4.4. Surface Width ................................................................................................................. 20

5 Condition Feasibility by Treatment............................................................... 25



5.1. Asphalt Overlays............................................................................................................. 25

5.2. Asphalt and Shape Correctors ....................................................................................... 25

5.3. Bitumen Treated Base Treatments ................................................................................ 26

5.4. Reseals ........................................................................................................................... 27

5.5. Seal widening ................................................................................................................. 27

6 Conclusions .................................................................................................... 30

Appendix A – Site Photographs................................................................................. 32



1 Executive summary

The Enhanced Road Condition Project (ERCP) was an initiative of the Department of Transport and Main Roads (DTMR) to demonstrate the perceived benefits of alternative strategies for the planning and delivery of programmed maintenance and rehabilitation of road pavements. In essence the project involved the delivery of a 10 year program of capital maintenance works, largely within the first two years of the cycle.

The benefits of the project were said to center around preventive maintenance. Works carried out earlier in the maintenance intervention cycle would be cheaper and produce an asset in better condition over the cycle. The economies of scale brought about by an enhanced maintenance budget in the early years would allow for non-traditional treatments such as specialist rehabilitation treatments.

Several feasibility studies were prepared by DTMR prior to commencement of the project in 1998. They involved the modeling of a base case and alternative (accelerated) maintenance strategies in order to demonstrate the benefits of the project as well as establish performance and feasibility criteria for the project.

These studies were used as part of the tender preparation of the project. The feasibility studies concluded that an accelerated program of works would lead to user and agency benefits and an asset in no worse condition than the current maintenance strategy.

The road network in Southern Burnett was chosen largely on the basis of its existing condition. It was considered to be (as a whole) within the realm of the early intervention part of the maintenance cycle. There were few road sections at or beyond serviceable life, and very little need for capital works.

The winning contractor, a consortium of private contractors lead by Boral Asphalt known as the BMC Consortium, prepared a program of works and feasibility study that predicted a significant improvement when compared to DTMR studies. The consortiums’ use of asphalt overlays, Bitumen Treatment Base (BTB), profilographs and advanced leveling was regarded as superior to the other tenders in the project, and would deliver a significant benefit over the base case in terms of pavement serviceability (ride quality and lane width).

The consortium completed works by the end of 1999. A DTMR group was established to report on the performance of the project periodically. Several asset condition reports were prepared and these were largely focused on the performance of non traditional treatments.

Road condition data of the ERCP network was compared to the predictive condition feasibility criteria in order to compare actual with predicted performance and project success. This information was combined with a recent visit to the network to inspect its condition and with discussions on the network with maintenance staff to form several conclusions on the road condition:



o When compared to the base case scenario, roughness was significantly improved. An overall roughness of 68 NRM was achieved in the final year of the project.

o The project achieved a road network with greatly improved seal width characteristics;

o The rutting and cracking results were generally less than desirable. The works failed to achieve rutting performance criteria in the 10th year. This suggests that the original program of works was dedicated to improving road roughness as opposed to creating a durable (structurally sound) road network;

o The full depth BTB rehabilitation works were successful, and performed best on all indicators reported. Maintenance staff have reported that seals often fail on these sites due to difficulties with determining bitumen application rates; as a result, stripping and bleeding is common. It is not known if skid resistance is a problem on these surfaces. It is recommended that deflection and material testing of the BTB sites be carried out in order to provide further confidence for ongoing use of the treatment.

o Regional staff have suggested that the selection of sites for BTB treatment may have been misdirected somewhat by the requirement of rehabilitation and widen being the selection criteria for treatment. Some greater need sites missed rehabilitation because of an adequate existing seal width.

o The asphalt overlays were successful at reducing roughness but have not performed to expectations in other respects. Fatigue cracking is a problem, particularly on sites that have not been treated with a seal. The failures have been reported to have been caused by variability in placement depth of the overlay to correct for shape and cross fall deficiencies. This has lead to asphalt placed in thickness vulnerable to fatigue stress.

o The condition data results need to be viewed in the context of maintenance carried out after the initial construction years. Significant “non-scheduled” works were carried out to address structural defects that have arisen from the project works. For instance all sites treated with a 75-mm BTB treatment failed soon after construction and required remedial works to correct. A significant amount of insitu stabilisation works were carried out on Road Section 44A from chainage 8.0 to 16.0 to correct the poor performance of asphalt overlays.

o The contractor modeling of the program of works carried out by BMC Consortium proved to be accurate in relation to roughness and seal width predictions but less so for rutting and cracking. This may be due to the premature failures of asphalt related works.

Overall the project was successful at achieving a condition better than the base case. There were some premature failures of treatments, asphalt overlays and half depth BTB treatments that resulted in poor performance at the end of the project and this was likely due to improper design.

The program of works was directed at achieving a pavement with a high pavement serviceability standard and this was achieved. The overall level of rutting, cracking and roughness



deterioration in the network implies that a better result would have been achieved if resources and program of works was balanced more towards improving the structural deficiencies.



2 Introduction

2.1. Objectives

The objective of this document is to report on the performance and condition of the road pavement delivered under the ERCP in Southern Burnett Shire in 1999. The main focus will be on reviewing the assumptions and predictions made of the works program in the lead up to the project and how it compares to the actual condition. The assessment of performance will be made by:

o Comparing the condition feasibility criteria predictions established at the start of the project with the actual road condition;

o An assessment of the objective of achieving a preventative maintenance outcome. i.e. the use of earlier, less costly treatments earlier in the maintenance cycle to achieve efficiencies and improved pavement condition;

o An assessment of the performance of the individual job sites as well as the various non-traditional treatments: bitumen treated base (BTB) rehabilitation, asphalt overlays and asphalt correctors.

This report will use discussions with Regional and Local Government staff involved in maintenance to the road network as well as key condition and maintenance data to draw its conclusions.

Several economic predictions and assumptions were made, that related to efficiencies in costs (of bulking up works and in the method of delivery) these are not in-scope to the current report and will not be addressed.

2.2. Background

The ERCP was an initiative of the DTMR and Treasury to determine the benefits of alternative strategies for the planning and delivery of programmed maintenance and rehabilitation of road pavements.

The project trialed the effectiveness of bringing forward capital maintenance works traditionally executed over a ten year cycle to within the first two years of the cycle.

The project had specific goals:

o To test whether non traditional patterns of funding could establish economies in the delivery of maintenance type projects;

o To test the concept of bringing forward works to achieve economies in the life cycle costing of road maintenance. i.e. the use of earlier, less costly treatments than traditionally been performed;



o To achieve economies of scale from the grouping of similar maintenance projects and;

o To allow for innovative products and processes in the maintenance of the road network.

The road network was chosen largely on the basis of its existing condition. It was considered to be (as a whole) within the realm of the early intervention part of the maintenance cycle. There were few road sections at or beyond serviceable life, and very little need for capital works.

After extensive planning and tender evaluation process the contract was awarded to a private consortium of contractors known as the BMC consortium lead by Boral Resources. An evaluation panel established to assess the merits of tender proposals found that BMC’s proposal was superior to others in several key respects:

o The use of quality materials and innovative treatments (BTB rehabilitation);

o Superior preliminary designs and 20 year design life of BTB treatments;

o The use of state of the art roughness control technology in overlay placement, generally not available on rural road networks;

o Superior organisational arrangements;

Works to the Southern Burnett road network was complete by the end of 1999. To maximize learning’s from the project a monitoring group was established to carry out performance evaluations to the network periodically over the next ten years. Several reports have been tabled, primarily focused on the performance of the non-traditional treatments.

This report will for part 2 of a final year 10 assessment of the project. The other parts will address the economic benefits, design and construct delivery mode as well as feedback from stakeholders.

2.3. Location and Program of Works

The ERCP road network is located within the current Wide Bay/Burnett Main Roads Region. It currently also lies within the two local government jurisdictions: Southern Burnett Regional Council and Gympie Regional Council. It consists of all or part of 40C, 41A, 45A and 45B and represents approximately 260km of road network. Some short sections within the network were excluded due to earlier programmed capital works (mainly realignments) at these locations. The location and program of works, (as-constructed plan) is presented in figure 2.0 below.



Figure 2.0: As-constructed works ERCP Project



In order to provide a sense of the scale of works carried out, table 2.0 quantifies each treatment in terms of the road lengths.

As-constructed Road Length (km)

Treatment No Widening

Includes Widening

Reseal 115.6 6.6 Shape Correction and Seal 2.6 0 Asphalt Overlay 37.7 3.2 Shape Correction and Asphalt Overlay 0.6 0 Asphalt Shape Correction 27.7 0 Full Depth BTB Treatment 0 41.2 Half Depth BTB Treatment 7.8 0 Excluded/No Treatment 15.5 0

Totals: 207.5 51.0

Table 2.0: As constructed Road lengths of ERCP Maintenance Works

Actual treatment Length Road No 40mm AC Overlay 6.181 40C 40mm AC Overlay (max 55mm) 1.32 40C 40mm Asphalt overlay 3.546 44A 40mm Asphalt overlay 1.86 45A 40mm Asphalt overlay 5.33 45B 40mm Asphalt overlay (max 55mm) 0.7 45A 40mm Asphalt overlay (max 55mm) 1.18 45B 70mm BTB overlay with 1m Gravel overlay on shoulder 4 45A 75mm BTB overlay with 1m Gravel overlay on shoulder 3.8 45B Asphalt shape correction 6.89 40C Asphalt shape correction 3.82 41A Asphalt shape correction 10.5 45A Asphalt shape correction 4.8 45B Asphalt shape correction & 25mm Asphalt Overlay 0.55 40C Asphalt shape correction- No spray seal (to reduce 1.17 40C Geofabric & 50mm Asphalt overlay 3.19 45B Ponding correction & Geofabric & reseal 1.815 45B Reseal 19.595 40C Reseal 0.67 41A Reseal 23.619 44A Reseal 22.46 45A Reseal 20.52 45B Reseal & Shape Correction (15mm) 1.08 44A



Reseal (polymer) 3.84 45B Reseal 1999 0.685 40C Reseal 1999 11.69 41A Reseal 1999 2.95 45B Reseal 2000 2.55 45B Reseal 2001 2.1 44A Reseal 2006 6.61 45B Shape Correction & Geofabric & seal 0.3 45B Single Layer Asphalt overlay & Seal 11.855 44A Widen & 145mm BTB 8.3 44A Widen & 14mm Seal (8.5m) 5.56 41A Widen & Asphalt overlay (max 75mm) 0.175 41A Widen & BTB 3.68 40C Widen & BTB 21.18 41A Widen & BTB 7.06 45A Widen, asphalt shape correction (20mm) & seal (8.5 2.735 41A Widen, Shape Correction & 10mm Seal (8.5m) 1.28 44A Widen, Shape Correction & 10mm Seal (8.5m) 1 45A

242.146

Table 2.1: As constructed Road Works of ERCP

2.4. Road Environment

The ERCP network services the Southern Burnett rural district connecting the townships of Kingaroy, Goomeri, and Nanango with the Toowoomba Region and Warrego Highway in the South and South West, Brisbane, and the South East as well as the Bruce Highway in South East.

Traffic volumes are mid range between 1000- 5000 AADT, 3.5% of which are commercial vehicles. Growth in traffic volumes are moderate, in the range of 2.5% for commercial vehicles and 3.5% for vehicles overall. The traffic is predominately generated by the local community and industry, with a minor contribution from tourism and Inter-regional travel.

According to the Bureau of Meteorology, the region’s long term average rainfall is 780mm per annum. Drought has prevailed for most of the ERCP period with rainfall falling to 60% of the long term average; for 2005, rainfall was below 25% of the long term average.



3 Project Feasibility Studies

3.1. DTMR Feasibility Studies

Several feasibility studies were prepared by DTMR prior to the commencement of the tender process. The aim of the studies was to determine the base case capital and maintenance expenditure for the project as well as model the potential benefits that may be achieved by an accelerated maintenance program.

The results of the studies are presented in two main reports:

o The Enhanced Road Condition Project – Base Case Study Report, September 1996;

o The Enhanced Road Condition Project – Base Case Alternatives Study Report, December 1996.

The Base Case Study Report modeled a desirable, and conventional, maintenance strategy in order to determine the level of capital and maintenance expenditure (feasibility criteria) available to the ERCP project as well as the road conditions (condition feasibility) required to be achieved.

The Base Case Alternative Study Report predicted the likely outcome of an accelerated program of works to the asset condition. Two cases were examined; the first (case A) involved an accelerated program utilising conventional treatments, generally available to the study road network, and a second (case B) included an accelerated program with a wider selection of treatments, selected to maximise benefits to the road user.

3.1.1. Base Case Study

The base case predictions (pavement deterioration, maintenance requirements, and life cycle costs) were produced with Main Roads’ PAMINET system.

The base case maintenance and rehabilitation strategy was defined to be the elimination of identified pavement deficiencies as soon as available funding was allowed. Base case maintenance standards were established to represent both mandatory standards (which must be observed as soon as funding is made available) and desirable standards (which are observed wherever possible where funding allows). The mandatory standards apply to the seal type and surface width. Desirable standards apply to pavement condition triggers such as surface age, strength, roughness and rutting.

For example, a mandatory asphalt surface was selected for all town centers, while spray seals were used for all rural locations. Similarly mandatory seal widening was selected for any treatment triggered on sites with a seal width of less than 6.2m. The desirable standards related to surfacing age, strength and condition criteria. For instance reseals were triggered every seven years, sites beyond the desirable deflection for past traffic were selected for strengthening, sites with roughness greater than 160 NRM were selected for shape correction.



Once the potential candidates for treatment were selected using PAMINET, field inspections of the network were carried out to moderate and determine the appropriateness of the selected treatments. Treatment and their lengths were adjusted in accordance with field conditions, traditional job lengths, and programming.

Expenditure, over the ten years was determined by committee with Treasury Officials. The expenditure was determined on the basis of likely maintenance expenditure available for the road network.

3.1.2. Base Case results

The network feasibility criteria was determined by calculating and aggregating the present worth of the base-case capital and maintenance costs over the ten year period, discounting the yearly costs to the present (then 1996) dollars using a 6% discount rate. Routine maintenance costs were treated in a similar manner. The estimated present worth (1996 dollars) of all capital maintenance was found to be $19.01m. Similarly, the estimated present worth of all routine maintenance was found to be $3.64m. This value became the feasibility criteria, the contractor had to demonstrate that the value of works would be the same or less.

The end condition criteria (condition and surface width) were determined for each specified prediction year by calculating the length-weighted average of each performance attribute along each road.

Table 4.0 below sets out the upper and lower limits of road condition the contractor must achieve, or better, in order to have met the condition feasibility criteria.

3.1.3. Base Case Alternatives Study

Two alternatives to the base case funding were explored:

o Case A: accelerated timing of traditional treatments: that included only treatments and intervention standards for the base-case study, with the traditional funding regimes removed. The cost efficiency of bulking works into larger than traditional projects, as well as reflecting this in a likely lower unit rate, in the first two years of the cycle were explored.

The principle treatments adopted for use in the base case study are: reseals, thin AC surfacing (through centers) and for minor corrector courses, widenings, and granular overlay.

o Case B, where alternative treatments were combined with accelerated cash flow. This case represents the same approach as Case A with a wider range of treatments made available to select for each site. The selection of alternative treatments was made in order to maximize the overall benefits to the road user, rather than selecting a suitable program of works alone.



The alternative treatments to this Case Study included AC overlays in rural areas, where the Base Case Study restricted AC overlays to town centers; In-situ granular recycling with 2 coat PMB seal; these treatments included a selection of insitu granular recycling depths depending on the nature of the site, finally granular overlays with 2 coat PMB seal.

In both cases the present worth budget limits were derived from the base case study and were not to exceed $19.01m for rehabilitation and capital maintenance works, and $3.64m for routine maintenance works. Capital maintenance expenditure was maximised in the first two years of the 10 year cycle. Case A was required to achieve both the feasibility and condition criteria and Case B was required to meet condition, feasibility criteria and select treatments that maximised overall community benefits (road agency and community costs).

3.1.4. Base Case Alternative Results

The length weighted average conditions of the base case alternative studies were produced for all prediction years. These values are presented below as table 4.0.

The reports made the following conclusions:

o Each study case proved a substantial economic and community benefit over the base case. Study case B would offer the most beneficial program; a result that was expected as the program was designed to seek the greater economic benefit;

o Study case A resulted in a network in no worse condition than the base case. Study case B resulted in a moderately better network than the base case.

o Study case B demonstrated that the project constraints are somewhat incompatible. When community benefits are maximised not all parts of the road network will end up in a better condition, especially under financial constraints;

o Study case B, overall, achieved the goal of “accelerated preventative” maintenance – a more effective investment program which shifts the emphasis away from corrective maintenance work towards simpler, cheaper preventative maintenance works scheduled earlier in the pavement life cycle.

o Study case A has had less opportunity to show improvement as it was constrained to using traditional treatments, but with earlier timing. Nevertheless, some benefits are demonstrated, but with no significant improvement in overall network condition at year 10.



End Condition Feasibility Measures

Roughness (NRM) Av. Rut Depth (mm) Cracking Extent (%) Condition Quality Index (CQI)

Weighted Surface Width (m) Prediction

Year Road

Section Base Case

Case A

Case B

Base Case

Case A

Case B

Base Case

Case A

Case B

Base Case

Case A

Case B

Base Case

Case A

Case B

40C 95 81 70 6.7 4.3 2.1 7.1 1.5 0 51 69 81 7.7 7.7 8.3 41A 111 82 88 9.1 5.1 1.7 5.3 1.8 0 41 63 77 6.2 7.2 7.4 41B 167 124 169 11.5 4.5 12.1 13.7 0 22.3 14 52 13 5.8 6.6 5.8 44A 102 76 97 6.9 4.1 2.7 8.6 0 0 51 71 75 6.9 7.4 7.3

45A 84 79 82 5.7 3.7 1.3 3.1 0 0 63 75 81 7.7 7.9 8.2

45B 83 73 75 4.8 3.4 2.2 4.2 0 0 68 78 85 7.8 7.8 7.8

2 (1998)

Network 95 81 85 6.8 4.3 2.3 5.9 1.5 0.7 54 69 78 7.2 7.6 7.7

40C 87 86 77 5.2 4.5 2.3 4.3 2.4 0 60 70 81 8.5 8.5 8.3

41A 125 89 96 10.2 4.8 2.7 13.6 8.6 0 38 66 72 6.2 7.3 7.5 41B 136 135 156 5.2 5.3 2.8 0 0 0 52 51 42 6.6 6.6 6.6 44A 109 84 106 6.1 5.2 3.6 7.4 0 0 58 70 66 7.1 7.5 7.3 45A 85 86 90 4.2 4.3 1.9 0 0 0 72 74 79 8 8 8.2

45B 82 80 82 3.9 4.0 2.7 0.8 0 0 71 75 77 7.8 7.8 7.8

5 (2001)

Network 98 86 93 5.9 4.5 2.7 5.1 2.4 0 60 70 74 7.4 7.7 7.8

40C 99 100 87 3.9 4.3 2.5 0 2.7 0 69 65 77 8.5 8.5 8.3 41A 96 99 101 3.6 3.4 2.0 0 0 0 65 68 70 7.6 7.6 7.5 41B 160 164 159 6.3 6.2 0.6 12.4 35.8 0 36 32 42 6.6 6.6 6.6 44A 102 94 110 4.1 4.1 2.7 7.6 3.9 0 61 67 61 7.4 7.5 7.3

45A 101 100 97 4.9 4.9 1.8 4.9 4.4 0 62 61 75 8 8.0 8.2

45B 96 94 90 4.3 4.6 2.6 0.6 0 0 66 68 69 7.8 7.8 7.8

10 (2006)

Network 104 100 99 4.3 4.3 2.2 3 2.7 0 64 65 69 7.8 7.8 7.8

Table 4.0: Condition Feasibility Criteria (Base Case) and DTMR Modeling outcomes



3.2. Contractor Feasibility Studies

Two feasibility reports were prepared by the BMC consortium. The first report was submitted as part of a tender proposal and included a program of works along with predictions of asset performance. The second report was produced in 1999. It outlined a revised program of works and predictions following changes to the budget, road network and some input into the program of works from regional staff.

The BMC consortium proposal and post construction feasibility study were reported in:

o Feasibility Study and Report. Enhanced Road Condition Project – Project Number 73/45A/19, prepared by CMPS&F January 1997;

o Report on Remodeling of Pavements for Enhanced Road Condition Project – Project Number 73/45A/19, prepared by Egis Consulting Australia October 1999.

3.2.1. BMC Consortium Feasibility Study

The feasibility study and report presented a works program that would significantly improve the road condition to beyond that predicted by DTMR in its feasibility studies. The main benefit involved the use of materials and technology that would promote roughness reduction and seal width improvement above the other issues. Traditionally, significant use of asphalt materials, profilographs with advanced automated leveling has not been available for works in South Burnett. The ERCP funding arrangements allowed the consortium to establish a local asphalt plant and dedicated construction crew to achieve the results. The BMC Consortium claimed that their construction methods and materials would achieve roughness counts of 50-60 NRM regardless of the initial road condition.

The availability of an asphalt plant and quarried products allowed the trial of BTB rehabilitation treatments. This involved the blending, in a controlled environment, of base material (usually recycled) with bitumen products to be used as a road base material on rehabilitation sites. The BMC consortium claimed that BTB rehabilitation would provide a network with deflection characteristics superior to conventional rehabilitation works and this would translate into road network with lower routine maintenance costs and longer serviceable life.

The total discounted cost of the capital maintenance works was $21.3m (compared to a base case of $19.01m) while the total discounted cost of routine maintenance was $2.3m (base case $3.64m). This represented an additional expenditure of $1.09m when compared to the base case, and was in excess of the feasibility requirements. BMC claimed that the additional cost would result in a substantial improvement in road network condition and represent a premium in benefit for the cost involved.

The results of the pavement performance model carried out by BMC consortium is presented in the table 4.1 below. The Base Case results, that conducted by DTMR is presented for comparison.



3.2.2. Revised As-constructed Feasibility Study

Following the award of the contract, BMC consortium in conjunction with DTMR revised the original program of works to accommodate changes to the available funding, road network exclusions and the advice from regional staff. The program of works was re-modeled by BMC consortium using the same model and assumptions used in the feasibility study.

The results (condition feasibility) declined slightly from that of the original proposal but were still significantly better than the base case. These revised predictions are presented in table 4.1 below as the “As-Con Report”.




Roughness (NRM) Av. Rut Depth (mm) Cracking Extent (%) Condition Quality Index (CQI) Weighted Surface Width (m) Prediction Year

Road Section

Base Case

Tender Feasibility

Report

As-Con Report*

Base Case

Tender Feasibility

Report

As-Con Report*

Base Case

Tender Feasibility

Report

As-Con Report*

Base Case

Tender Feasibility

Report

As-Con Report*

Base Case

Tender Feasibility

Report

As-Con Report*

40C 95 55 58 6.7 2.2 3.0 7.1 0.5 0.4 51 94 88 7.7 8.4 8.4

41A 111 55 57 9.1 3.0 3.1 5.3 0 0 41 87 91 6.2 8.0 8.0

41B** 167 55 11.5 1.7 13.7 0 14 100 5.8 7.4

44A 102 55 57 6.9 3.1 3.6 8.6 0 0 51 92 89 6.9 7.7 7.7

45A 84 56 58 5.7 3.5 3.6 3.1 0.1 0 63 85 90 7.7 8.4 8.4

45B 83 59 62 4.8 3.4 3.6 4.2 0.1 0 68 89 89 7.8 7.9 7.9

Year2 (1998)

(2001 for as-con)

Network 95 56 59 6.8 3.0 3.3 5.9 0.1 0.1 54 90 87 7.2 8.0 7.8

40C 87 60 62 5.2 2.6 3.4 4.3 0 0 60 89 86 8.5 8.5 8.5

41A 125 59 61 10.2 3.5 3.7 13.6 0 0 38 90 90 6.2 8.2 8.2

41B** 136 59 5.2 2.3 0 0 52 90 6.6 7.6

44A 109 60 61 6.1 3.5 4.0 7.4 0 0 58 88 86 7.1 7.8 7.8

45A 85 61 63 4.2 4.0 4.1 0 0 0 72 88 87 8 8.5 8.5

45B 82 64 66 3.9 3.8 4.0 0.8 0 0 71 87 84 7.8 8 8.0

Year5 (2001)

(2004 for as con)

Network 98 61 63 5.9 3.5 3.7 5.1 0 0 60 88 84 7.4 8.2 7.9

40C 99 68 71 3.9 3.0 3.9 0 0.3 0.9 69 78 71 8.5 8.7 8.7

41A 96 67 69 3.6 3.9 4.1 0 0 0 65 70 71 7.6 8.4 8.4

41B** 160 67 6.3 2.8 12.4 0 36 80 6.6 7.8

44A 102 68 69 4.1 3.9 4.5 7.6 0.1 0.1 61 70 71 7.4 8.1 8.1

45A 101 69 71 4.9 4.5 4.7 4.9 0.1 0.1 62 76 75 8 8.7 8.7

45B 96 73 75 4.3 4.2 4.4 0.6 0.5 0.4 66 69 72 7.8 8.1 8.1

Year 10 (2006)

(2009 for as-con)

Network 104 69 71 4.3 3.9 4.2 3 0.2 0.3 64 72 70 7.8 8.4 8.1

Table 4.1: Condition Feasibility Criteria (Base Case) and BMC Consortium Modeling outcomes

* The Prediction years for the as-con have been moved forward to reflect the project commencement in 1999. The comparison to the previous predictions is still largely valid.

** The final as-constructed length on road 41B was 100m. Road 41B was excluded in the post-construction analysis.



4 Condition Feasibility Criteria Outcome

Road Condition data of the ERCP network was compared to the predictive condition feasibility criteria in order to compare actual with predicted performance and project success.

4.1. Ride Quality

When compared to the base case scenario, ride quality (roughness) of the network has been significantly improved, and is largely sustained throughout the 10 year project period. The BMC consortium predictions of roughness for the study period proved to be very accurate when matched with actual roughness.

4.2. Structural Performance

Deflection testing was not carried out at year 10 for this study, the level and extent of rutting and cracking has been taken as the indicator for structural performance. A result that achieved or bettered the base case results for rutting and cracking would indicate a pavement performing at its desirable structural capacity.

The rutting results, as presented in table 4.2 and chart 4.1, reveals that the base case was achieved in years 2 and 5 but not achieved in year 10. Moreover the data shows an improvement in rutting between year 2 (4.8mm) and year 5 (3.3mm) then a significant decline in year 10 (6.9 mm).

It is not clear why rutting should improve in year 5 when compared to year 2. It may be due to corrector courses and reseals and other routine maintenance carried out in the subsequent years or improvements to edge drop-offs and shoulder repairs to the asphalt overlay sections.

The cracking results, as presented in chart 4.2, have revealed very little change between assessment years 2 and 5, at 0.9% and 1.0% respectively, then a substantial increase to 2.8% in year 10. Despite this relatively rapid rate of increase, the cracking results have appeared to have achieved the condition feasibility criteria.

The relatively rapid change in rutting and cracking between years 5 and 10 is of interest. More than 98% of the road network was either resealed or reconstructed for the project. A soundly designed, constructed and maintained pavement seal should show negligible signs of cracking in the first 10 years of serviceable life. According to model deterioration rates, cracking onset commences in year 10 of pavement life.

Moreover the rutting and cracking results need to be viewed in the context of maintenance carried out after the initial construction years. Regional maintenance staff have stated that significant “non-scheduled” works were carried out under routine maintenance contracts to address specific structural defects that have arisen from the project. For instance all sites treated with a 75-mm BTB treatment fatigued soon after construction and required remedial treatments. A significant amount of insitu stabilisation occurred on Road Section 44A from



chainage 8.0 to 16.0 to correct poor performance from asphalt overly constructed under the project. (Plate A4 – Appendix A)

4.3. Condition Quality Index

The Condition Quality Index (CQI) is an amalgamation of all the road condition data. It scores each section of road pavement with a number between 0 and 100. A value of 100 would indicate a road in the best condition possible, a score of 0 would indicate a pavement in its worst possible condition.

A summary of all predictions and the outcome of CQI for the road network is presented in chart 4.3. Because of the poor rutting results, and to some lesser extent cracking, the project failed to achieve or better the base case result in year 10.

4.4. Surface Width

The ERCP had a significant effect on improving the lane widths of the road network and the base case was achieved and bettered in all years. A final year 10 result of 9.0-m weighted average seal width was achieved against a base case of 7.8-m. The results are presented in chart 4.4. The results would also indicate that further widening works, likely programmed within routine maintenance, has been carried out after the ERCP works.




Roughness (NRM) Av. Rut Depth (mm) Cracking Extent (%) Condition Quality

Index (CQI) Weighted Surface

Width (m)

Prediction Year

Road Section

As-constructed Treatment

Section Length (km) Base

Case Outcome Base Case Outcome

Base Case Outcome

Base Case Outcome

Base Case Outcome

40C 40.07 95 63 6.7 4.3 7.1 0.5 51 74 7.7 8.8

41A 45.83 111 58 9.1 4.8 5.3 0.1 41 75 6.2 8.2

41B** 0.10 167 11.5 13.7 14 5.8

44A 51.78 102 55 6.9 5.5 8.6 3.8 51 64 6.9 7.4

45A 47.58 84 55 5.7 4.6 3.1 0.1 63 77 7.7 7.8

45B 56.89 83 58 4.8 5.2 4.2 0.6 68 75 7.8 8.9

Year2 (1998)

(2001 for as-con)

Network 242.25* 95 55 6.8 4.8 5.9 1.0 54 71 7.2 8.0 40C 40.07 87 58 5.2 3.5 4.3 2.2 60 78 8.5 9

41A 45.83 125 59 10.2 2.6 13.6 0.3 38 85 6.2 8.4

41B** 0.10 136 5.2 0 52 6.6

44A 51.78 109 59 6.1 3.9 7.4 1.5 58 76 7.1 7.4

45A 47.58 85 53 4.2 3 0 0 72 88 8 8.2

45B 56.885 82 61 3.9 3.9 0.8 0.9 71 78 7.8 9.1

Year5 (2001)

(2004 for as con)

Network 242.25* 98 63 5.9 3.3 5.1 0.9 60 79 7.4 8.2 40C 40.07 99 62 3.9 6 0 1.6 69 63 8.5 10.7

41A 45.83 96 65 3.6 6.6 0 0.8 65 68 7.6 8.7

41B** 0.10 160 6.3 12.4 36 6.6

44A 51.78 102 71 4.1 8.5 7.6 2.8 61 55 7.4 8.2

45A 47.58 101 60 4.9 6.8 4.9 2.1 62 66 8 8.6

45B 56.885 96 66 4.3 7.2 0.6 6.6 66 52 7.8 10.3

Year 10 (2006)

(2009 for as-con)

Network 242.25* 104 68 4.3 6.9 3 2.8 64 59 7.8 9.0

Table 4.2: Condition Feasibility Criteria (Base Case) and Outcome

* Total as-constructed final length was 242.15km, excluding road 41B.

** The final as-constructed length on road 41B was 100m. Road 41B was excluded in the post-construction analysis.



Feasibility Studies - Roughness Predictions

0

20

40

60

80

100

120

Prediction Year

Net

wor

k R

ough

ness

(NR

M)

Base Case 95 98 104

Case A 81 86 100

Case B 85 93 99

Tender Feasibility Report 56 61 69

As-Con Report* 57 61 69

Outcome 55 63 68

2 (1998) 5 (2001) 10 (2006)

Chart 4.0 Roughness Predictions vs. outcome

Feasibility Studies - Rutting

0

2

4

6

8

Prediction Year

Aver

age

Rut D

epth

(mm

)

Base Case 6.8 5.9 4.3

Case A 4.3 4.5 4.3

Case B 2.3 2.7 2.2

Tender Feasibility Report 3 3.5 3.9

As-Con Report* 3.3 3.7 4.2

Outcome 4.9 3.4 7.1

2 (1998) 5 (2001) 10 (2006)

Chart 4.1 Rutting Predictions vs. Outcome



Feasibility Studies - Cracking Predictions

0

2

4

6

8

Prediction Year

Cra

c C

rack

ing

Exte

nt (%

)

Base Case 5.9 5.1 3

Case A 1.5 2.4 2.7

Case B 0.7 0 0

Tender Feasibility Report 0.1 0 0.2

As-Con Report* 0.1 0 0.3

2 (1998) 5 (2001) 10 (2006)

Chart 4.2 Cracking Predictions vs. Outcome

Feasibility Studies - Condition Quality Index

0

20

40

60

80

100

Prediction Year

Con

ditio

n Q

ualit

y In

dex

(CQ

I)

Base Case 54 60 64

Case A 69 70 65

Case B 78 74 69

Tender Feasibility Report 90 88 72As-Con Report* 87 84 70Outcome 73 81 60

2 (1998) 5 (2001) 10 (2006)

Chart 4.3 CQI Predictions vs. Outcome



Feasibility Studies - Weighted Surface Width (m)

0

2

4

6

8

10

Prediction Year

Wei

ghte

d Su

rface

Wid

th (m

)

Base Case 7.2 7.4 7.8

Case A 7.6 7.7 7.8

Case B 7.7 7.8 7.8

Tender Feasibility Report 7.8 7.9 8.1

As-Con Report* 7.8 7.9 8.1

Outcome 8.0 8.2 9.0

2 (1998) 5 (2001) 10 (2006)

Chart 4.4 Weighted Surface Width Predictions vs. Outcome



5 Condition Feasibility by Treatment

The condition feasibility criteria have been compared to each treatment type. The aims of the analysis are to rank and weight each treatment, and determine its overall contribution to road condition. The length weighted average of condition for each treatment was collated and is presented on charts 5.1 to 5.4 below.

5.1. Asphalt Overlays

Asphalt overlays were designed using a DG10 asphalt mix at a minimum depth to achieve a smooth non-structural wearing course. In rural areas the overlays were spray sealed for additional protection against water penetrating the surface. In urban areas no seal was applied to minimize noise. The original intent was to lay the asphalt to a depth no greater than 55-mm.

The asphalt overlays were successful at reducing the roughness to below base case levels for the duration of the project. However roughness deterioration rates, as presented in chart 5.0, are high compared to other treatments, and the base case. Rutting and cracking rates, as presented in charts 5.2 and 5.3, are high and did not achieve the base case results.

Cracking was particularly problematic in townships, where asphalt overlays were constructed without seals. The seals on the asphalt overlays appeared to be necessary to prevent moisture infiltrating in the pavement and maintain structural performance. (Plate A2 – Appendix A)

Discussions with regional maintenance staff have confirmed that the treatments were not successful, and often required remedial works to repair fatigue and other failures. The causes of the failures have been traced to design. The original intent was to construct a non-structural overlay less than 55-mm in depth. Because of poor cross fall and shape however the actual depth, on some sections, varied significantly, resulting in the thicker asphalt sections sensitive to effects of tensile strain in the lower layers and hence fatigue. (Plate A1 – Appendix A)

Regional staff have also expressed some concern that the extensive sections of asphalt will present difficulties with resealing and reflective cracking in future; especially through townships where the problems are severe. They have suggested that a more conventional approach of granular overlays in place of the asphalt overlays would have been more desirable from a management perspective, albeit at the expense of a rougher road network. The advantages of granular overlays are in managing the consequences of failure, with simpler less costly remedial measures. Asphalt and BTB treatments are less forgiving and the original design is far more critical for a successful performance.

5.2. Asphalt and Shape Correctors

The shape correctors were selected to improve ride quality and cross fall, the thickness has been developed to ensure that the longitudinal profile is optimized.



Based upon the condition data provided the asphalt correctors experienced similar problems as the asphalt overlays, but to a less degree. Roughness and rutting deterioration rates are high.

5.3. Bitumen Treated Base Treatments

Bitumen Treated Base (BTB) is a plant mixed material, consisting of quarried and graded base material mixed with bitumen content of approximately 3.5% depending upon design. It is placed on a pre-prepared sub base and shoulders. The treatment is subsequently spray sealed to provide a wearing course.

The full depth BTB treatments were designed to a 20 year design life standard. For the ERCP project full depth varied from 130-mm to 185-mm depending on subgrade CBR and future traffic. It was the view of BMC Consortium that the only treatment during the design life is a reseal at around year 12. At worst the pavements would have reached their fatigue design life around years 15 and 20 and would require a SAMI and 50-mm asphalt overlay. This however would have been extended if the reseal at year 12 was a PMB seal to stop reflection cracking.

The candidate sections for BTB treatment were selected on the basis of poor deflection and seal width characteristics. Regional staff present during the program development of the project have suggested that the seal width restriction of selecting rehabilitation sites may have lead to some misdirection in sites selected for treatment; greater need sites were not rehabilitated because seal width was adequate.

The half depth BTB treatments, which were under designed at depths of up to 75-mm were acknowledged by regional staff to have been experimental. All sites required extensive remedial works, soon after the project completion, to address failures associated with fatigue. The roughness deterioration rates are the highest when compared to other treatments and this is despite the remedial works.

The full depth BTB sites have proved to be successful and contributed most to pavement stability and serviceability. BTB sites had the lowest roughness and roughness deterioration rate at approximately 0.62 NRM counts per year. They have the lowest level of cracking and rutting, which indicates good structural performance.

Regional maintenance staff have confirmed the quality of the works. The only difficulties with the treatments are with determining suitable bitumen application rates for sealing. The porous nature of the material have caused seals to bleed and strip resulting in a motley appearance of stripped aggregate between wheel paths and bleeding along the wheel paths. This was confirmed by recent site inspections on BTB sites that where the original seal is still in place. Despite the poor seal condition, water ingress, does not appear to have affected pavement stability. (Plate A3 – Appendix A)

It is not known if the poor seal performance of these sites has contributed to skid resistance problems.



It is recommended that deflection testing, along with suitable material testing be carried out over these areas to determine a remaining useful life. The data and analysis will provide further confidence for ongoing use of the treatment.

Roughness Deterioration 2001 - 2009

0 0.5 1 1.5 2 2.5

BTB Full Depth

Reseal

Base Case

Asphalt Overlay

Asphalt Shape Correction

BTB Half Depth

Trea

tmen

t

Roughness Counts (NRM/yr)

Chart 5.0 Roughness Deterioration Rates

5.4. Reseals

The reseals were designed in accordance with standard Main Roads Practice. Candidate sites were selected on the basis of age and condition (field inspection).

The reseals largely met the base case performance criteria, but did not meet the base case requirements for rutting in the 10th year. Despite the results for rutting, reseal have largely performed to expectations.

5.5. Seal widening

The average seal width of the road network increased to an average of 9-m as a result of the ERCP project and further maintenance works. The benefits of the improvements to reducing overall routine maintenance costs have been acknowledged by regional staff. However savings brought about by improvements to shoulder widths may have been offset by addition costs of maintaining the asphalt overlay sections.



Roughness by Treatment Type

0

20

40

60

80

100

120

Year

Roug

hnes

s (N

RM) Base Case

Asphalt OverlayAsphalt Shape CorrectionBTB Full DepthBTB Half DepthReseal

Base Case 92 99 100

Asphalt Overlay 73 76 81

Asphalt Shape Correction 56 57 67

BTB Full Depth 52 55 57

BTB Half Depth 55 63 73

Reseal 64 64 72

2001 2004 2009

Chart 5.1 Roughness by Treatment Type

Average Rutting by Treatment Type

0

1

2

3

4

5

6

7

8

9

Year

Aver

age

Rutti

ng (m

m)

Base caseAsphalt OverlayAsphalt Shape CorrectionBTB Full DepthBTB Half DepthReseal

Base case 6.8 5.9 4.3

Asphalt Overlay 5.5 3.4 6.4

Asphalt Shape Correction 5.0 3.0 7.0

BTB Full Depth 3.8 1.7 5.5

BTB Half Depth 3.9 2.6 6.8

Reseal 5.3 4.1 7.9

2001 2004 2009

Chart 5.2 Average Rut Depths by Treatment Type



Cracking by Treatment Type

0

2

4

6

8

10

12

14

Year

Crac

king

(%)

Base CaseAsphalt OverlayAsphalt Shape CorrectionBTB Full DepthBTB Half DepthReseal

Base Case 5.9 5.1 3

Asphalt Overlay 1.1 3.1 11.8

Asphalt Shape Correction 0.3 0.5 0.7

BTB Full Depth 4.4 0.1 0.9

BTB Half Depth 0.0 1.0 2.5

Reseal 0.4 0.8 1.6

2001 2004 2009

Chart 5.3 Cracking by Treatment Type

CQI by Treatment Type

0

20

40

60

80

100

120

Year

CQI I

ndex

Base CaseAsphalt OverlayAsphalt Shape CorrectionBTB Full DepthBTB Half DepthReseal

Base Case 54 60 64

Asphalt Overlay 68 69 45

Asphalt Shape Correction 73 86 63

BTB Full Depth 77 96 81

BTB Half Depth 87 78 56

Reseal 70 76 57

2001 2004 2009

Chart 5.4: CQI by Treatment Type



6 Conclusions

o Roughness was significantly improved. An overall roughness of 68 NRM was achieved in the final year of the project.

o The project achieved a road network with greatly improved seal width characteristics;

o The rutting and cracking results were generally less than desirable. The works failed to achieve rutting performance criteria in the 10th year. This suggests that the original program of works was dedicated to smoothening the road network as opposed to creating a durable (structurally sound) road network;

o The full depth BTB rehabilitation works were successful, and performed best on all indicators reported. Maintenance staff have reported that seals often fail on these sites due to difficulties with determining bitumen application rates; as a result, stripping and bleeding is common. It is not known if skid resistance is a problem on these surfaces. It is recommended that deflection and material testing of the BTB sites be carried out in order to provide further confidence for ongoing use of the treatment.

o Regional staff have suggested that the selection of sites for BTB treatment may have been misdirected somewhat by the requirement of rehabilitation and widen being the selection criteria for treatment. Some greater need sites missed rehabilitation because of an adequate existing seal width.

o The asphalt overlays were successful at reducing roughness but have not performed to expectations in other respects. Fatigue cracking is a problem, particularly on sites that have not been treated with a seal. The failures have been reported to have been caused by variability in placement depth of the overlay to correct for shape and cross fall deficiencies. This has lead to asphalt placed in thickness vulnerable to fatigue stress.

o The condition data results need to be viewed in the context of maintenance carried out after the initial construction years. Significant “non-scheduled” works were carried out to address structural defects that have arisen from the project works. For instance all sites treated with a 75-mm BTB treatment failed soon after construction and required remedial works to correct. A significant amount of insitu stabilisation works were carried out on Road Section 44A from chainage 8.0 to 16.0 to correct the poor performance of asphalt overlays.

o The contractor modeling of the program of works carried out by BMC Consortium proved to be accurate in relation to roughness and seal width predictions but less so for rutting and cracking. This may be due to the premature failures of asphalt related works.

Overall the project was successful at achieving a condition better than the base case. There were some premature failures of treatments, asphalt overlays and half depth BTB treatments that resulted in poor performance at the end of the project and this was due to improper design.



The program of works was directed at achieving a pavement with a high pavement serviceability standard and this was achieved. The overall level of rutting, cracking and roughness deterioration in the network implies that a better result would have been achieved if resources and program of works was balanced more towards improving the structural deficiencies.



Appendix A – Site Photographs



Plate A1 - Asphalt overlay and seal on Road 40C D’Aguilar Highway (Yarraman to Kingaroy) Tdist 8.4 km

Variable thickness in design has resulted in poor performance. Photo illustrates fatigue reflective cracking appearing through the seal as well as extensive rutting.



Plate A2 - Asphalt overlay without seal in Township of Yarraman on Road 40C D’Aguilar Highway

The spray seal on the asphalt overlays appeared to have made an important contribution to preventing moisture ingress into the pavement and fatigue failure.



Plate A3 – Full Depth BTB site and original seal on Road 40C D’Aguilar Highway Tdist 49 km.

The full depth BTB sites are all in good condition, and have maintained stability since construction. The photo illustrates stripping between wheel paths. Regional maintenance staff have had difficulties in

designing suitable bitumen application rates when designing seals for these sites. Pavement stability has not been affected by the poor seal performance.



Plate A4 – Insitu stabilisation works on Road 44A Wide Bay Highway (Gympie to Goomeri) Tdist 8–16km

Remedial works carried out during the 10 year project to correct problems associated with Asphalt overlays.

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