Session 5 Techniques for Determining Pavement/ Treatment Feasibility

Learning Objectives 1.State steps in the treatment selection process 2.List advantages and disadvantages of decision trees and matrices Upon completion of this module, you will be able to:

Learning Objectives (cont.) 3.Identify cost analysis tools 4.Use LCC and cost/effectiveness to evaluate strategies

Is this pavement a good candidate for PM? If so, how do I determine what PM treatments to apply… and when?

Selecting Pavements & PM Treatments 1.Gather information 2.Assess condition 3.Evaluate data 4.Identify/project pavement needs 5.Identify feasible PM treatments 6.Conduct cost/effectiveness analysis 7.Select “best” strategy

Step 1. Gather/Review Available Pavement Information  Pavement type  Pavement age vs. design life  Traffic  Environment  Structure and materials  Construction quality

Step 2. Assess Current Pavement Condition  Identify current distresses (severity and amount)  Is the pavement in relatively “good” condition?  Are there any structural failures?  Minimal previous repairs?

Step 3. Evaluate Data  Too much distress?  Underlying structural problems?  Missed PM “window of opportunity?”  Material or construction problems?  Problems in this environment?  Typical performance of this type of pavement?

Step 4. Identify/Project Pavement Needs A.Identify current pavement needs   Preservation?   Maintain or reach acceptable LOS? B. B.Anticipate potential future problems (structural, functional)

Step 5. Identify Feasible PM Treatments

Characteristics Influencing Feasible Alternatives  Pavement type  Traffic  Environment  Past treatment performance  Ease of application  Cost  Material and contractor availability

Existing Methods of Identifying Feasible Alternatives  Lists of acceptable treatments  Time-based schedules  Decision tools  Decision trees  Decision matrices

Lists of Agency-Accepted Treatment Types  Agency PM guidelines  Organized by category  Pavement type  Traffic level  Pavement condition  Others?

Michigan Acceptable PM Treatments Rigid Pavements   Full-depth repair   Joint resealing   Crack sealing   Joint & surface spall repair   Dowel bar retrofit   Diamond grinding   Underdrain outlet repair and cleaning   CPR   Bit. shoulder ribbons Flexible and Comp. Pvmts.   Bituminous overlay   Milling & bit. overlay   Ultra thin overlay   Crack treatment   Overband crack filling   Microsurfacing   Chip seals   Bit. shoulder ribbons   Shoulder seals   Paver placed surface seals   Hot in-place bit. recycling

Time-Based Schedules  Set schedule of PM treatments  Based on pavement type and age  Corrections?

Time-Based Schedule Example New York State-Initial Guidelines Treatment Type Appl. Cycle, yrs  PCC pavement joint and crack sealing  HMA pavement crack sealing  Thin HMA overlays (38 mm [1.5 in])  Surface treatments of HMA pavements  Surface treatments of shoulders  Clean drainage

Time-Based Schedule Example Province of Ontario (Freeways)–PCC Design Life (yrs) Year of Treatment Maintenance Treatment Reseal 10% of all joints Reseal 20% of all joints REHABILITATION Reseal 10% of all joints Reseal 20% of all joints REHABILITATION

Other Time-Based Examples  South Dakota  Crack sealing: 1 to 2 years  Chip seal: 3 years  Montana  Chip seal: 6 to 8 years  Thin overlay: 10 to 12 years

Decision Trees / Matrices  Identify one or more acceptable PM treatments  Consider characteristics such as:  Pavement type  Distress type and level, or index values  Traffic volume  Functional classification

HMA Decision Tree Example Prev. Maint. Treatment Surface Wear Severity Env. Cracking Extent Fatigue Crack Extent Rutting Severity Structural Deterioration Crack Seal Surface Treatment Crack Seal + 40 mm O/L Crack Seal + 40 mm O/L Mill and Fill 50 mm Mill and Fill 40 mm Mill and Fill 50 mm Mill and Fill 50 mm Prev. Maint. Treatment Mill and Fill 40 mm Mill and Fill 50 mm Mill and Fill 75 mm Mill 50 mm + 75 mm O/L Mill 75 mm mm O/L Mill 100 mm mm O/L Mill 100 mm mm O/L Total Reconstruct Rem. HMA, Rep Base, Repave Low Moderate High Low Moderate High Low Moderate High Low Moderate High Low Moderate High Low Moderate High Low Moderate High Low Moderate High YesNo

Fog Seal or Chip Seal Fog Seal or Chip Seal or Microsurfacing Fog Seal or Microsurfacing ADT < to 5000>5000 HMA Decision Tree Example Raveling and Weathering Not Appropriate for Preventive Maintenance Structural Condition Adequate Not Adequate

HMA Decision Matrix Example DistressSeverity Treatment Type Flushing/Bleeding ModerateN/ARLRL SevereRLRLRL10-12 Non-Structural Cracking MinorN/A Moderate Severe FL InsufficientStructure MinorRL Moderate FL Severe FL Bad Ride MinorN/ARLRL ModerateRL SevereRL Unstable Base and Subgrade MinorRL Moderate Severe FL Unstable Mix Minor Moderate8-12FL Severe8-12FL AgedPavement Minor Moderate Severe FL Surface Raveling MinorN/A Moderate3-6 Severe8-12 Do Nothing Spot Repair Seal Coat Micro Surface Cold Recycle Surface Mill Thin Overlay FD Mill & O/L Part Mill & O/L Reconstruct Crack Filling Rut Mill Thick Overlay DistressSeverity Treatment Number and Type Flushing/BleedingModerateN/ARLRLRL Severe Non-Structural Cracking MinorN/A3-5 Moderate3-5 Severe InsufficientStructureMinorRL Moderate2-6 Severe Bad Ride MinorN/ARL Moderate Severe Do Nothing Spot Repair Seal Coat Micro Surface Cold Recycle

HMA Decision Matrix Example Seal Coat Slurry Seal Microsurfacing TrafficADT< >ADT<5000ADT>5000RMNRRMNRRRR BleedingRRR RuttingNRRR RavelingRRR Cracking Few tight cracks Extensive cracking RRRNRRNR Improving Friction YesYesYes Snow Plow Damage Most susceptible Moderately susceptible Least susceptible R = Recommended; NR = Not recommended; M = Marginal

Benefits of Decision Trees/Matrices  Make use of existing experience  Work well for local conditions  Good as a project-level tool

Limitations of Decision Trees/Matrices  Transferability between agencies  Limits innovation  Does not incorporate all factors  Difficulty with multiple distress types  Does not identify most cost-effective strategy  Not good for network evaluation

Developing Decision Tools Considerations  Select treatments for pavement types  Identify criteria that affect feasibility  Pavement age  Key distresses  Structural vs. functional  Threshold levels  Traffic volumes

Developing Decision Tools Class Exercise 1.Pick a pavement type 2.Select typical or desired treatments 3.Identify criteria that affect feasibility 4.Create a decision matrix 5.Create a decision tree

Step 6. Conduct Cost/Effectiveness Analysis

Cost/Effectiveness Analysis Introduction  Determine treatment costs and life expectancy data for YOUR agency  Previous projects  Pavement management records  Different cost and cost-effectiveness analysis approaches  Assessment of cost-effectiveness requires determination of benefits

Common Cost Analysis Methods  Equivalent annual cost (EAC)  Longevity cost index  Life cycle cost analysis (LCCA)  Benefit/cost analysis

Equivalent Annual Cost  Requirements:  Unit cost of equipment, workers, and materials per day (or contract)  Expected life of treatment  Output:  Unit cost per expected life of treatment

Equivalent Annual Cost unit cost of treatment expected life, years EAC =

Longevity Cost Index  Requirements:  Treatment unit cost  Traffic loading  Treatment life  Output:  Relates present value of treatment cost to life and traffic

Longevity Cost Index Price/sy + MCOST/sy Life*Annual MESALs LCI =

Longevity Cost Index  Advantages  Straightforward means of determining cost effectiveness  Disadvantages  Requires inputs that may not be easy to determine (e.g., ESALs)  Comparing benefits?

Life Cycle Cost Analysis  Most common approach for comparing alternative strategies  Evaluates all costs over analysis period  Uses equivalent dollars to compare expenses incurred at different times  Does not account for varying levels of service

Life Cycle Cost Analysis Methods  Present worth (PW)  Equivalent uniform annual cost (EUAC)

Life Cycle Cost Analysis Requirements  Discount rate = Interest Rate – Inflation Rate  Analysis period  Unit cost for treatment  Estimated life of treatment

Present Worth Method Takes a series of costs: And converts costs to one point in time: $ *Comparisons require similar analysis periods

Computing Present Worth Costs PW = C 11 (1 + i) n where: PW=Present worth cost C=Future cost n=Number of years (time in future when C is applied) i=Discount rate

Equivalent Uniform Annual Cost Method Takes a series of costs: And converts costs to an equivalent series of payments: $ $ $ $ $

Computing Equivalent Uniform Annual Costs EUAC = PW i (1 + i) n (1 + i) n – 1 where: EUAC=Equivalent uniform annual cost PW=Present worth cost n=Analysis period i=Discount rate

Advantages and Disadvantages of LCCA  Advantages  Familiar method  Inputs fairly easy to quantify  Variability can be evaluated  Disadvantages  Pavement condition (benefit) not considered in analysis

Benefit/Cost Analysis  Considers both the cost and effectiveness of a treatment  Costs determined using LCCA  Effectiveness accounts for performance and users impacted  Approach is used in many PMS

Condition Benefit What is Benefit? Condition Benefit Benefit = Area Time

Condition Benefit What is Benefit? Condition Benefit Benefit = Area Time

Benefit/Cost Comparison Strategy Preventive Maint. Rehabilitation Benefit Cost, $M $0.5 $ = 500 PM Strategy: B/C = = 286 Rehab Strategy: B/C =

Benefit/Cost Strategy On A Network Level  Highest Benefit/Cost Ratios The most cost-effective strategies are selected

Benefit/Cost Analysis  Advantages  Considers costs and benefits  Use of pavement management systems  Disadvantages  More complex than other methods  Often difficult to quantify benefits

LCCA Example Problem Definition  Compare two feasible PM strategies for an HMA pavement and determine which has the lowest life-cycle costs  Strategy A: Treatment 1 repeated every 6 years  Strategy B: Treatment 2 repeated every 4 years

LCCA Example General Assumptions  Benefits are considered to be the same for both alternatives  First PM applied at year four  20-year analysis periods  Routine maintenance applied annually  User and rehab. costs not included

Gather Information General Cost Information  Initial costs = $400,000  Discount rate = 4%

Gather Information Strategy Details  Strategy A  Treatment 1 life = 6 years  Treatment 1 cost = $30,000 /app.  Annual maintenance costs = $500  Strategy B  Treatment 2 life = 4 years  Treatment 2 cost = $12,000 /app.  Annual maintenance costs = $800

Cost Stream Summary Initial Construction = $400,000 (yr 0) Treatment 1 = $30,000 (yrs 4, 10, & 16) Routine Maintenance = $500/yr (yrs 1-19) Salvage Value = (2/6)*$30,000 = $10,000 (yr 20) Define Cost Streams Define Cost Streams Strategy A Time $30,000 $400,000 $500/yr $10,000 $30,000

Cost Stream Summary Initial Construction = $400,000 (yr 0) Treatment 2 = $12,000 (yrs 4, 8, 12, & 16) Routine Maintenance = $800/yr (yrs 1-19) Salvage Value = $0 Define Cost Streams Define Cost Streams Strategy B Time $12,000 $400,000 $12,000 $800/yr

Compute Costs Strategy A PW (initial)=$400,000 PW (routine maint.)=$6,567 PW (treatment 1)=$61,928 PW (salvage value)=$– 4,564 Total PW=$463,931 EUAC=$34,137 Discount Rate = 4%, Analysis Period = 20 yrs

Compute Costs Strategy B PW (initial)=$400,000 PW (routine maint.)=$10,507 PW (treatment 2)=$32,928 PW (salvage value)=$0 Total PW=$443,435 EUAC=$32,629 Discount Rate = 4%, Analysis Period = 20 yrs

Interpret Analysis Results Strategy No. Strategy Description EUAC 1 Strategy A $34,137 2 Strategy B $32,629 Strategy B is the preventive maintenance strategy with the lower life cycle costs.

Step 7. Select “Best” Strategy  Total available funds  Timing considerations  Cost-effectiveness  Other factors

Review of Learning Objectives 1.State steps in the treatment selection process 2.List advantages and disadvantages of decision trees and matrices 3.Identify cost analysis tools 4.Use LCC and cost/effectiveness to evaluate strategies