BLOCK 4 SELECTION OF THE PREFERRED ALTERNATIVE Pavement Data Collection Project evaluation Select...
-
Upload
oscar-leo-howard -
Category
Documents
-
view
218 -
download
0
Transcript of BLOCK 4 SELECTION OF THE PREFERRED ALTERNATIVE Pavement Data Collection Project evaluation Select...
BLOCK 4SELECTION OF THE
PREFERRED ALTERNATIVE
Pavement DataCollection
Projectevaluation
Select feasiblealternatives
ReconstructionRestorationRecyclingResurfacing
Life-cyclecosts
Non-monetary
factors
Select preferred
alternative
Detailed PS & E
Construction
MonitorPerformance
Module 4-1
Selection of the Selection of the Preferred Rehabilitation Preferred Rehabilitation
AlternativeAlternative
Learning Objectives
• Define life-cycle cost analysis and some of the key computational variables.
• List major LCCA cost items for agency and user.
• Differentiate between probabilistic and deterministic LCCA.
• Identify treatment selection factors other than costs.
• Describe a process to evaluate multiple alternatives.
What Is Life Cycle Costing?• An economic analysis
– Compares design or rehabilitation alternatives
– Considers all significant costs– Evaluates the alternatives over the
same analysis period• Analysis approaches
– Deterministic– Probabilistic
Importance of LCCA
• All costs can be taken into account
– Agency costs
– User costs
– Salvage value
• Alternate strategies can be compared
– On an equivalent basis
– Based on assumptions made
Significance of LCCA
Time
Rehabilitation
Salvage
Construction
Maintenance
Time
RehabilitationPreventiveMaintenance
Salvage
Construction
Routine Maintenance
Present Worth Method
Takes a series of costs:
And converts costs to one point in time:
$
Equivalent UniformAnnual Cost Method
Takes a series of costs:
And converts costs to an equivalent series of payments:
$ $ $ $ $ $ $ $ $ $
Inputs to the LCCA Process• Agency costs
– Initial
– Future M & R
• Analysis Period
• Performance Period
• Nominal vs. Constant Dollars
• Discount Rate
• Salvage Value
• User Costs
Agency Costs
• Initial Construction Costs
– Overhead
– Design
• Future Maintenance and Rehab
• Where do these costs come from?
Analysis Period
• Time period over which future costs are evaluated
• Length of analysis period
– Long enough to reflect cost differences
– Force use of each rehabilitation alternative
Analysis Period vs.Performance Period
Co
nd
itio
n
Time
Analysis Period
2nd RehabPerformance
Period
1st RehabPerformance
Period
Nominal vs. Constant Dollars
• Nominal (inflated) dollars
– Future costs are inflated
• Real (constant) dollars
– Future costs are the same as current costs
• Use consistent dollars and discount rates in LCCA
Discount Rate• Time value of money
– $1 today is not worth $1 a year from now due to interest and inflation
• Significant effect on LCCA• Should reflect long-term historical trends• Discount Rate = (Int. – Infl.) / (1 + Infl.)
~ (Int – Infl.) Int. = Interest Rate (Treasury note)
Infl. = Inflation Rate (Consumer Price Index)
• FHWA suggests values in 3 to 5% range
Real Discount Rate
Amount Lostto Inflation
Real Discount RatesSource: OMB Circular A-94
Investment Maturity
YEAR 3 5 7 10 30
Feb 93 3.1 3.6 4.0 4.3 4.5
Feb 94 2.1 2.3 2.5 2.7 2.8
Feb 95 4.2 4.5 4.6 4.8 4.9
Feb 96 2.7 2.7 2.8 2.8 3.0
Feb 97 3.2 3.3 3.4 3.5 3.6
2001 3.2 3.2 3.2 3.2 3.2
Avg 3.1 3.3 3.4 3.5 3.7
(No Inflation Premium)
Effect of Discount Rate
• Costs occurring earlier are valued more
• Future costs are valued less
• Thus:
– Low rates favor high initial costs and lower future costs
– High rates favor lower initial costs and higher future costs
Salvage Value
• Residual Value
– Actual generated value
– e.g. recycling
• Serviceable Life
– Ratio of remaining years to life, times cost
0
10
20
30
40
50
60
70
80
90
100
5 10 15 20 25 30 35 40 45
Salvage ValueAnalysis Period
Time
Co
nd
itio
nResidual Value Illustrated
User Costs: A Closer Look
• Traffic delay costs
• Vehicle operating costs
• Crash costs
• Damage to freight
User Costs• Costs incurred by user over analysis period• Types:
– User delay costs– Vehicle operating costs– Crash costs
• Models available for calculation (MicroBenCost, QueWZ, HDM-IV)
• May overwhelm overall LCC (particularly on high volume roadways)– Should keep separate from other costs
Measures of User Costs
Hours Stuck in TrafficJams
Driving the Open Road
Source: TTI
Least Congested Cities, Annual
An Indication of Crash Costs
Median Jury Awards for all Traffic Crash FatalitiesRose 102% from $288,000 in 92 to $ 581,000 in 95.
Higher Traffic Fatality Awards
Source: Jury Verdict Research
Probabilistic LCCA
• “Risk-based” analysis
• Addresses variability of inputs
• Inputs needed
– Mean or expected value
– Standard deviation or range
– Type of distribution (typically normal distribution assumed)
Probabilistic LCC Results
0%
10%
20%
30%
$ Millions
Frequency
A
B
2223
PW Cost Distributionof Two Alternatives
FHWA Recommendations
• LCCA encouraged
• As noted in TEA-21...
– LCCA not required
– Recommendations on LCCA to be developed for States
– In conjunction with Executive and AASHTO guidelines
Treatment Selection Factors
• Available Funds
• Staged Construction
• Traffic Control
• Lane Closure
• Minimum Desired Life
• Future Maintenance
• Geometric Issues
Treatment Selection Factors (continued)
• Present and Future Utilities
• Right-of-Way Restrictions
• Regulatory Restrictions
• Available Materials and Equipment
• Contractor Expertise and Manpower
• Agency Policies
Selection Process• Develop feasible alternatives for
evaluation
• Identify key decision factors important to agency (e.g., cost, service life, traffic control, duration of construction, etc.)
• Assign weighting values for each decision factor
• Assign scoring values for each alternative
• Add scores and rank alternatives
Selection Worksheet
DecisionFactor 1
Decision Factor 2
Decision Factor 3
DecisionFactor 4
TOTAL SCOREWeight Weight 1 Weight 2 Weight 3 Weight 4
Alt 1
Alt 2
Alt 3
Alt 4
Weighting Factors
• Relative (weighted) importance of factors considered in selection process
• Number and types of factors will vary
• Should reflect an agency’s decision process
• Sum of all weighting factors must equal 100
Scoring Factors
• Feasible treatments scored comparatively against weighting factors
– e.g., lowest cost gets highest rating
• Somewhat subjective process
• Based on agency’s own experience
• Use whatever scale is appropriate (1-5, 1-10, 1-100, etc.)
Computing Scores
• Product of rating factor and scoring factor
• Computed for each treatment
• Treatment with highest total score is considered the “best” treatment for the specific project
Example Selection Worksheet
TOTAL SCOREWeight
Alt 1
Alt 2
Alt 3
Alt 4
60 50 8050
50 75 7070
40 75 6080
30 100 5090
30 12.5 12 5 59.50
25 18.75 10.5 7
61.25
20 18.75 9 8 55.75
15 25 7.5 9 56.50
LCCService
LifeTraffic Control
Reliable Design
50% 25% 15% 10%
Review
• What are some of the key computation variables in a life-cycle cost analysis?
• What are some major LCCA cost items for both the agency and the user?
• How does probabilistic LCCA differ from deterministic LCCA?
• What are some treatment selection factors other than costs?
Key References• Peterson, D. E. 1985. Life-Cycle Cost
Analysis of Pavements. NCHRP Synthesis of Highway Practice 122. Transportation Research Board, Washington, DC.
• Walls, J. and M .R. Smith. 1998. Life-Cycle Cost Analysis in Pavement Design—Interim Technical Bulletin. Federal Highway Administration, Washington, DC.