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Chapter I – Whole Life Costing

Chapter I - Whole Life Costing January 2005

Table of Contents Chapter 1 – Whole Life Costing

1. Whole Life Costing ……………………………………………………………………. 1

2. Saving money: asphalt structure is a mean …………………………………………. 4

3. Quality of the materials ………………………………………………………………. 5

4. Strengthening …………………………………………………………………………. 5

5. Flexible pavement for lightly trafficked roads ……………………………………… 6

6. Indirect saving: availability of performance ………………………………………… 6

7. Life cycle costing ………………………………………………………………………. 7

8. Example: Benelux Bitume whole life costing study for the ring of Antwerp (2002) 8

9. Conclusions ……………………………………………………………………………. 9

10. References ……………………………………………………………………………... 9

Annex: Whole Life Costing Study Ring Antwerp by Benelux Bitume (2002) ………... 11



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Chapter I - Whole Life Costing

1. Whole Life Costing With all governments experiencing competition for financial resources, policy makers need to be assured that money spent is both cost-effective and necessary. This is particularly true with transport where spending on highways is always under close scrutiny and funds rarely meet the transport demands. In order to better justify road construction schemes, it has become necessary to consider the whole life costs (WLC) of a planned road from the initial construction stage through to the planned maintenance intervals over a design life of usually between 20 and 30 years and sometimes more.

If the philosophy is that roads are likely to last for 20 years, then, in the simplest scenario, it could be assumed that one twentieth of the road network is likely to require some kind of treatment every year. A study carried out in Australia identified various treatment costs to maintain a highway in a serviceable condition [19].

The theory underpinning whole life costing is that costs are discounted over the design life of the road (20, 30 or 40 years). The discount rate is expressed as a percentage and is usually set at a number of rates. Knowing initial costs of construction and the costs likely to be incurred at the planned maintenance stages, a whole life cost of the road over its design life can be determined. With this in mind, it is clear that a longer life design, which does not lead to a corresponding increased initial cost and/or a reduced maintenance strategy, which does not compromise on road performance, will appear a better option in the WLC model. Even if, for example, the initial cost is slightly higher, but the expected life under a given traffic intensity is doubled, the WLC will be improved when compared with a construction with lower initial cost and an expected life only half the first option. By using whole life cost models, it should be easier to convince government agencies of the benefit of considering the longer term for highway construction and maintenance schemes.

In the asphalt industry, 20 years was traditionally taken as the period over which to calculate the whole life costs with two or maybe three planned maintenance intervals. With newer and better bituminous designs, it is now possible to design for a forty-year life with 3 or four planned maintenance stages, which has the net result of greatly improving the WLC. Inputs into a whole life cost model are numerous and it is possible to arrive at realistic values for various construction scenarios. As an example, Table 1 shows two designs and their WLC analyses [19].



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Table 1 - Whole of Life Cost

Design 1 Design 2

20 year design life, carrying 5,000,000 esa 20 year design life, carrying 10,000,000 esa

For both designs: Subgrade CBR (Californian Bearing Ratio): 5%, 50 mm SMA (Stone Mastic Asphalt) surface course, structural asphalt layer of modulus 3200 MPa (25°C)

REHABILITATION TREATMENT

Trigger: cracking > 30%, Rutting > 15 mm,

Roughness > IRI (International Roughness Index) = 4

Life Cycle Cost (AUD/m2) discounted over 40 years at:

Asphalt Concrete thickness

0%

4%

7%

10%

13%

Design 1

5 x 106 esa 200 mm 130 91.7 77.3 69.1 64.4

Design 2

107 esa

220 mm 93 76.1 70.3 67.2 65.4

AUD: Australian dollar (price level year 2000)

In the same paper, the cost of "repairing at observed failure" is estimated, in today’s money, to be AUD 5.25 per m2 per year. Using the WLC model, the annualised costs of maintenance management, as opposed to repair at failure policy, for the designs given in Table 1 are shown in Table 2.

Table 2 - Annualised Maintenance Management Costs

Life Cycle Cost (AUD/m2) discounted over 40 years at:

Asphalt Concrete thickness 0% 4% 7% 10% 13%

Design 1

5 x 106 esa 200 mm 3.25 2.29 1.93 1.73 1.61

Design 2

107 esa 220 mm 2.33 1.90 1.76 1.68 1.64



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Calculation of whole life costing needs models which integrate the different parameters and provide the costs of each step. This should include indirect impacts and has the final aim of defining a construction, maintenance and rehabilitation policy. Figure 1 illustrates the content of this type of model [1], [2], [3], [4], [5].

Figure 1 - Components of a whole life costing system [5]

Among the existing construction types, asphalt structures offer the widest variety of alternative answers to solve local problems.

In the opinion of many designers and contractors, asphalt structures significantly reduce initial and total costs over the entire life cycle of a road [6].

For the duration of the considered period, asphalt pavements keep traffic running smoothly with occasional limited cost for maintenance to the top layer. It also permits possible overlaying to add structural capacity which can handle any unexpected increase in traffic loading.

Beyond this period, pavement life is maintained through defining the planning stages of reinforcement in accordance with the estimated budget (figure 2).



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Figure 2

All these points are developed in the following paragraphs.

2. Saving money: asphalt structure is a mean Technical advantages of asphalt structures have an effect upon the global cost of a pavement including building, maintenance, rehabilitation and indirect costs (such as road users’ costs) [6[, [7], [8], [9], [15], [16].

Road pavements are submitted to the effects of traffic loading and also to climatic factors with consequent variation in the damage they cause, depending of the type of structure.

Without explaining the mechanical behaviour of a pavement which is widely described in the chapter "Pavement design", it is important to mention some important points which are specific to bituminous materials.

The advantages of asphalt structures are mainly linked to the visco-elastic behaviour of bitumen and to the ease of controlling layer thicknesses. The following points are worth considering:

• Large range of bituminous materials provides the most suitable answers [10];

• The mechanical properties needed before trafficking are reached within a short time scale after the construction or the reinforcement (normally hours, versus days for cement concrete);

• Wide range of possibilities in planning the reinforcement stages;

• Bonding of the asphalt layers together which ensures continuous transfer and relaxation of the stresses inside the pavement which is crucial for the life expectancy;

• Easy recycling of the bituminous materials, hot or cold, in-situ or in a mixing plant, saves money and preserves non-renewable natural resources;

• Ease of trenching the urban road network with limited impact on pavement life span (asphalt concrete and mastic asphalt);

• Reinforcement does not need steel or heavy wire mesh, which drives up the initial cost for cement structures;

• Limited damage caused to the structure by corrosive effects of de-icing salts through cracks and joints which might cause full reconstruction in cement concrete pavements;



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• On environmental issues, some Research Centers such as the Center for Transportation Research at the University of Texas, or the Arizona Transportation Research Center find that the roadside noise levels with asphalt pavements are definitely lower than for concrete pavements. The Transportation Research Board (TRB) estimates that this effect can allow the use of lower sound barriers with consequent cost savings. An example has shown that a reduction in noise level of 5.6 dB allows a reduction in barrier height of 2 feet which saved some 10 million dollars per year. A lot of research has also been done in the Netherlands as shown in references [20], [21] and [22]. When the pavement reaches the end of its life, the bituminous base can typically be left in place with rehabilitation being limited to normal overlaying with an eventual surface treatment. With cement concrete, it needs to be completely broken up or removed for a total reconstruction;

• The presence of any cement concrete layers in the pavement will require its complete break-up or removal at the end of its life-time. Reinforcement of "old" cement concrete structures by asphalt top layers are only short-term solutions that will not last;

• Skid resistance that lasts long-term (10 years and more) can be achieved with Porous Asphalt and BBTM (Béton Bitumineux Très Mince – Very thin Bituminous Layers) without need of grooving (dangerous for motorcycles) [23].

3. Quality of the materials In common with every composite material, there is a close relationship between the composition of the mixture and its ultimate mechanical properties. Regular quality control of the bituminous binders and adjustment of the plant mixes will guarantee production of asphalt concrete with mechanical performance that comply with those determined for the theoretical compositions designed in laboratories.

This is of prime importance in managing both the initial construction and any subsequent reinforcement. If this is not achieved, then neither the recommendations of the pavement design will be met, nor will they be cost effective.

4. Strengthening One of the major parameters of the pavement design, for initial construction as well as for the strengthening, is the adequate prediction of traffic loading which is generally expressed as the number of "standard axles".

Sometimes, it is difficult to make a reliable forecast of the traffic, which can increase faster than the estimates. A typical illustration of this is the opening of the European Community road-network to heavy traffic whose growth is not predictable as it depends on the economies of individual countries.

Under-estimating the traffic loading has a major effect on the pavement life which is derived from calculation. Unexpectedly high trafficking will certainly mean pavements will require early strengthening which of course has a consequent financial impact.

When compared with rigid structures which are very sensitive to their thickness, the eventual, gradual strengthening of asphalt structures is easier due in part to lower thicknesses. The mechanical behaviour, failure modes and maintenance/repair of these two different types of pavement gives cost advantage to the asphalt construction.



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Despite large increases in traffic volumes, there appears to be no technical limit to the use of asphalt in providing solutions to meet these extra demands [24], [25], [26], [27].

As demonstrated, in most practical cases, the process of strengthening must be considered in the evaluation and comparison of the global cost of each equivalent road pavement structure. This should occur at the design stage.

5. Flexible pavement for lightly trafficked roads Light traffic is considered to be less than 50 equivalent standard design axle loads to which the pavement will be subjected per day, during its design life. A large proportion of the road network falls into this category: for example in France, more than 60% of the road network qualifies.

An example comparing total construction and maintenance costs between flexible and rigid pavements handling light traffic has been carried out using the LCPC design methodology [11].

In this framework, from the available hydraulic materials, only concrete has been considered. For these types of structure, hydraulic bases courses such as "grave-cement" are unsuitable because:

- A minimum overlaying thickness of 150 mm is required for these road materials;

- Treatment of reflective cracking dramatically increases the maintenance which would otherwise normally be limited with these pavements;

- It is difficult to carry out work on smaller sites.

The main conclusions of this comparison are:

- Lower total costs are obtained with flexible structures particularly when considering the lowest traffic levels and sub-grades with highest stiffness moduli;

- Similar maintenance costs for both structures;

- The large range of possibilities for gradual strengthening and technical potential for adapting the thickness of bituminous pavements to compensate for increased traffic loads;

- The increased risk of premature damage due to sub-optimal design of rigid pavement structures. Often the design parameters are inaccurate, a situation that is not uncommon with these kinds of pavements (traffic predictions, soil mechanical characteristics…).

6. Indirect saving: availability of performance The expected increase in traffic over the following years make the managers of the infrastructures consider the impact of the maintenance steps, environmental effects such as noise, emission of polluting gases by delayed vehicles, and loss of economic productivity (non-productive travel time and freight) [12], [13]. All these elements related to increased traffic levels, cause higher costs for road users (i.e. tax payers).

Delayed deliveries due to road works can lead to significant costs. For example, in the United States of America, a simple construction on a busy interstate highway can cost the local economy more than 2 million US dollars per day (price level: year 2000) [15].

Another example from a survey in Texas revealed that values of time lost at roadworks for automobiles ranged between $8.7 to $12.6 per hour, and $21.1 and $26.4 for trucks (price level: year 1999) [18].



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Effects on human behaviour, of congestion due to construction, maintenance and rehabilitation are difficult to quantify. However some studies of driver behaviour indicate a direct relationship with a variety of adverse physiological conditions such as anti-social habits or tendencies, aggressive behaviour and stress-related health effects [13].

For all these issues, politicians have made it clear that these impacts on road users cannot be neglected and have to be taken into account in the choice of road construction engineering.

Asphalt materials are ideally suited to reducing the traffic disturbances:

- The required performance is obtained immediately after cooling with hot mixes or breaking of emulsion with cold mixes;

- During construction and maintenance, areas can be set up during off-peak hours when the traffic is low or if work must continue during rush hours, some lanes can be kept open;

- Rehabilitation does not need a complete reconstruction as it does when using cement concrete materials.

So, construction, strengthening and rehabilitation with asphalt construction have a more limited financial impact on the local economy.

7. Life cycle costing Life cycle costing involves direct and indirect outlays.

1) First come the initial construction, current wearing course maintenance and overlaying over a period which is generally between 20 and 30 years or possibly more.

2) The second are more difficult to estimate and generally not taken into consideration by the designers. Construction and maintenance have an effect on the local economy which cannot be neglected and consists of the environmental impacts (time costs, vehicle operating costs, accident costs, noise level…).

International literature only contains much data on direct costs [15], [16], [17], having been provided by many designers and contractors. Normally these figures are based on comparisons between equivalent pavements both in terms of bearing strength and service life expectancy.

Analysis of these figures leads to the following conclusions:

• When considering reflective cracking, semi-rigid structures are the most expensive to maintain whatever the life-time. Compared with a flexible structure, the consequence is an addition of 10 to 15% to the global cost;

• Over a period of 25 years and depending on the actual traffic, the global cost of asphalt structures is definitely less than cement concrete pavements. Some studies show differences in cost of up to 20%, sometimes even more!

• It is only when a 35-year maintenance period is considered, that the global costs of cement concrete pavements approach those of asphalt structures, but with significant increases in initial outlays for their construction;

• For low traffic levels, the comparison of flexible pavements and rigid pavements leads to the conclusion that the discounted total costs evaluated (on the basis of realistic assumptions) are still in favour of flexible pavements;



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• Recycling of asphalt concrete has been widely used for more than 20 years without particular technical difficulties. It reduces the need for aggregates (which are not always available in each area) and it contributes to protection of the environment;

• In most cases, the failure of concrete pavements requires full reconstruction of the road which implies extensive costs and lengthy consequences for traffic.

Interstate Highway 75 was constructed in 1966, partly of concrete and partly of asphalt. The Ohio Department of Transportation has quantified the costs of individual sections of this highway [17] and concludes that the main advantage of asphalt over cement is that concrete pavement will have to be reconstructed or replaced at the end of its life. Full depth asphalt roads do not normally reach this level of damage and so do not require major reconstruction.

Unless a particular thickness of structure needs to be kept, strengthening by overlaying according to pavement design practices is the normal form of rehabilitation.

Figure 3 [17]

Figure 3 shows a comparison of total contract costs for the similar asphalt and concrete pavements which were constructed in 1966: a dramatic increase in the cost for concrete pavement incurred in 1987.

The main conclusion from this example indicates that asphalt pavements can provide continuous service for 35 years or more with resurfacing after 12 or 15 years. There is no need for significant rehabilitation such as the removal of the base.

8. Example: Benelux Bitume whole life costing study for the ring of Antwerp (2002)

In 2002 Benelux Bitume made an economic calculation for the ring around Antwerp. Note that we considered only the initial investments and the maintenance for a lifetime of 40 years.

The work consisted of the renewal of 12 km highway and 30 km of side roads. Everything was broken up and renewed. Benelux Bitume suggested 230 mm of asphalt with a surface of SMA included. The concrete suppliers suggested 230 mm of continuously reinforced concrete on 60 mm of an asphalt base course. The proposed maintenance strategies were:

Asphalt:

• Every year: small maintenance; • After 15 years: mill out the wearing course and the upper binder course of the right lane

and renew them;



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• After 30 years: mill out the wearing course and upper binder course over the whole surface.

And so on.

Concrete:

• Every year: small maintenance; • After 40 years: concrete was broken up and renewed.

The annex of this chapter gives the outcome of this WLC study.

9. Conclusions Selecting a pavement structure requires consideration of the costs for the road construction, maintenance, rehabilitation and also the costs related to the road users.

Numerous examples and studies have concluded that the costs for asphalt structures are lower than those for cement structures, particularly when recycling and rehabilitation are taken into account.

Additionally one needs to consider the other advantages offered by asphalt pavements:

• Pavement rehabilitation with rigid structures requires it to be dug up, whereas with asphalt structures, resurfacing and overlaying can be used. Keeping the base intact is significantly cheaper and demonstrates that asphalt can be considered as a "perpetual pavement".

• For lightly trafficked roads, which are a large part of the road network, asphalt structures are clearly favourable in respect of their economical and technical advantages.

• Lower roadside noise levels of asphalt wearing course (compared with concrete) can save money in reducing sound barrier height.

• Asphalt is 100% recyclable and asphalt pavements can be stage-constructed, stage-maintained and stage-recycled. This makes it possible to cope with the uncertainties of the future.

• In every case, asphalt should be more economical to install and maintain over the life of the pavement, which is sometimes over 40 years.

10. References 1. Lee and Lauter: Using pavement manager system concepts to determine the cost and

impact of utility trenching on an urban road network – Transportation Research Record 1999, paper 00-0342

2. Zimmerman et al.: Applying economic concepts from life cycle cost analysis to pavement management analysis

3. Bull and Warwick: An approach to the life cycle cost analysis of alternative pavement types – Proceedings 16th ARRB conference, part 3

4. Papagiannakis & Delmar: Computer model for life cycle cost analysis of roadway pavements – Journal of computing in civil engineering 2001, vol. 15, No. 2

5. PIARC Report 08.09.B, 2000: Whole life costing of roads (flexible pavements)

6. Shmuck and Ressel: Cost effectiveness: a comparison of economic efficiency for different road pavement – 5th Eurasphalt Congress, p 286



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7. APA: Life cycle cost analysis

8. APA: From beginning to end, asphalt costs less

9. APA: Hot mix asphalt life cycle costs

10. Flexible Roads (C8 plenary session): Recommendations for road decision makers – XXIst World Road Congress 3 – 9 October 1999

11. Coussin, Michaut, Serfass: Chaussées souples et chaussées rigides à faible trafic. Contribution à la comparaison des coûts globaux de construction et d’entretien. Revue Générale des Routes et Aérodromes, n° 668, novembre 1989

12. Nigel S. Organ: Is DBFO and whole life costing the answer to future road construction? – Eurasphalt & Eurobitume congress 1996

13. Solstice: Legislation, Policy & Economics 15/11/01

14. Shell: Asphalt v Cement – Report SM/R/86/53

15. APA: Asphalt pavement life cycle cost. Background

16. Roude: Chaussées souples et chaussées rigides. Contribution à la comparaison de leurs coûts globaux de construction et d’entretien – Revue Générale des Routes et Aérodromes No. 660, février 1989

17. APA: Ohio asphalt interstates are long lasting and economical

18. Daniels, Ellis, Stockton: Techniques for manually estimating road user costs associated with construction projects – Texas Transportation Institute, December 1999

19. Yeaman J.: How long is "whole life" for pavements – 1st International Conference, World of Asphalt Pavements, 2000, Sydney

20. CROW: Het wegdek gecorrigeerd op akoestische eigenschappen (Pavements adapted for acoustic purposes, in Dutch). Publicatie 133 – 1999

21. Stille wegdekken zijn kostenefficiënte geluidsmaatregelen. M+P Raadgevend Ingenieurs (Cost effectiveness of low noise pavements, in Dutch) – 2000

22. Website: www.stillerverkeer.nl – CROW

23. Brosseaud Y., Abadie R. and Legonin R.: Very thin and ultra-thin bituminous concretes, specific properties and perspectives, in the Institute of Asphalt technology, Irish branch – Journée technique Dublin, 1996.

24. PIARC report 08.06.B, 2000: Choice of materials and design of flexible pavements for severe traffic and climates, page 171

25. EAPA: Heavy duty Surfaces, the arguments for SMA, ISBN 90 801214-8-7, 1998

26. EAPA: Heavy duty Roads, the arguments for Asphalt, ISBN 90-801214-6-0, 1995

27. CROW: Workshop Heavy Duty Pavements, October 1997, Ede



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Annex: Whole Life Costing Study Ring Antwerp by Benelux Bitume (2002) 1. Maintenance strategy

Table 1 -Asphalt with lifetime of 30 years

Year 5 10 15 20 25 30 35 40 Small maintenance 5% of the surface

New upper binder course right lane New wearing course SMA total width

New upper binder course total width New wearing course SMA total width

Table 2 - CRC with lifetime of 40 years

Year 5 10 15 20 25 30 35 40 Maintenance Reconstruction

2. Cost calculation Asphalt (Price level 2002)

Year 2002

Construction Unit Euro/unit Unit/m2 Euro/m2 Binder course AB3A (60 mm) Ton 46.15 0.15 6.92

Bond coat M² 0.15 1.0 0.15

Binder course AB3A (60 mm) Ton 46.15 0.15 6.92

Bond coat m² 0.15 1.0 0.15

Binder course AB3A (60 mm) Ton 46.15 0.15 6.92

Bond coat m² 0.15 1.0 0.15

Wearing course SMA (40 mm) Ton 59.20 0.1 5.92

Total 27.13

Years 2007, 2012, 2022, 2027, 2037, 2042

Small maintenance SMA (ca. 5% from the surface in 5 year) Unit Euro/unit Unit/m2 Euro/m2 Filling cracks m 1.36 0.2 0.01 Local surface treatment m² 2.70 1.0 0.14 Local repair SMA m² 10.55 1.0 0.53 Total 0.68



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Year 2017

New binder course right lane, New wearing course SMA total width

Unit Euro/unit Unit/m2 Euro/m2

Milling 40 mm total width m² 4.96 1.0 4.96 Milling 60 mm right lane m² 3.71 1.0 3.71*1/3 = 1.24 Construction binder course AB3A (60 mm) right lane Ton 46.15 0.15 6.92 *1/3 = 2.31Construction wearing course SMA (40 mm) Ton 59.18 0.1 5.92

Total 14.43 Year 2032

New binder course and new wearing course total width Unit Euro/unit Unit/m2 Euro/m2

Milling 100 mm total width m² 7.03 1.0 7.03

Construction binder course AB3A (60 mm) Ton 46.15 0.1375 6.35

Construction wearing course SMA (40 mm) Ton 59.18 0.1 5.92

Total 25.65 Concrete (Price level 2002)

Construction Unit Euro/unit Unit/m2 Euro/m2

Construction sublayer AB3A (60 mm) ton 66.79 0.15 10.02

Construction Continuously Reinforced Concrete m² 35.31 1.0 35.31

Total 45.33

Maintenance Unit Euro/unit Unit/m2 Euro/m2

Maintenance m² 0.02 1 0.02

Total 0.02

Reconstruction Unit Euro/unit Unit/m2 Euro/m2

Construction sublayer AB3A (60 mm) ton 66.79 0.15 10.02

Construction Continuously Reinforced Concrete m² 35.31 1.0 35.31

Total 45.33

Asphalt Pavement costs per m²

Costs per m² (price level 2002)

Construction 27.13 Small maintenance 5% of the surface 0.68 New binder course right lane New wearing course SMA total width 14.43

New binder course total width New wearing course SMA total width 25.65

Continuously Reinforced Concrete costs per m²

Costs per m²



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(price level 2002) Construction 45.33 Maintenance 0.02 Reconstruction 45.33

3. Comparison Comparison asphalt-concrete on 40 years

Construction Costs

5

10

15

20

25

30

35

40

Total maintenance

during 40 years

Total construction + maintenance 40

years

Asphalt 27.13 0.53 0.42 6.94 0.26 0.20 5.93 0.12 0.10 14.50 41.63

Concrete 45.33 0.02 0.01 0.01 0.01 0.01 0.00 0.00 6.44 6.50 51.83

Comparison asphalt-concrete on endless basis

Construction costs

Time cycle

Net constant value First cycle

Factor

Endless basis

Total maintenance

Endless basis

Total construction + maintenance Endless basis

Asphalt 27.13 30 year 14.50 1.30 18.85 45.98 Concrete 45.33 40 year 6.50 1.17 7.61 52.94

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