Life-Cycle Cost Analysis

Transcription

1 Life-Cycle Cost Analysis Tashia J. Clemons FHWA Office of Asset Management Pavement Preservation Expert Task Group Meeting Oklahoma City, OK May 3,

2 Agenda 1. Pavement Preservation 2. State Example 3. Resources 2

3 Pavement Preservation Keeping Good Roads Good 3

4 Pavement Preservation Doing the right thing... to the right pavement. at the right time... TO KEEP THE GOOD ROADS GOOD! 4

5 Case Study Section Lake County - District 1 State Route 53 7-mile long, 4-lane highway 5

6 Life Cycle Cost Analysis (LCCA) Life-Cycle Cost Analysis An economic analysis tool useful in comparing the relative economic merits of competing construction and rehabilitation design alternatives for a single project. Equivalent Uniform Annual Cost (EUAC): Represents the NPV of all discounted costs and benefits of an alternative as if they occur uniformly throughout the analysis period. 6

7 Caltrans Customized RealCost Life-Cycle Cost Analysis 7

8 CalME Version

9 Structural Design & Economic Analysis 9

10 CalME Design Inputs 10

11 Basic Definitions Maintenance and Rehabilitation action (M&R action) (e.g. 60mm HMA overlay, ) Maintenance and Rehabilitation strategy (M&R strategy) : series of M&R actions over an analysis period. Maintenance and Rehabilitation alternative (M&R alternative) (EPP 30mm HMA, etc ) 11

12 Application Hwy 53 in Lake County-11.27Km (PM0.0-PM7.00) 12

13 Project Information 4 lane-state Route 53 in Lake County, CA Climate characterized as Low Mountain (Characterized based on air temperature and precipitation) TI=14.2 (46.2 million ESAL s) for a 20 year design life The subgrade of the pavement is SW (R=37) 13

14 Distress Mechanisms Rutting Fatigue cracks Environment effects in aging 14

15 CalME Predicted Rutting Life-Cycle Cost Analysis 160 mm HMA Type ¾ AR mm AB Class 2 Subgrade SW (R=37) 15

16 CalME Predicted Cracking Life-Cycle Cost Analysis 160 mm HMA Type ¾ AR mm AB Class 2 Subgrade SW (R=37) Fatigue Cracking is the critical distress 16

17 Decision Trees Based on distress amount, material type, material thickness Extended Pavement Preservation (EPP): Repeated perpetually if: down rut 5 mm or cracking 0.25 m/m 2 : Use 30 mm HMA, RAC-G, or MB4 overlay (with or without milling) Rehabilitation (R): Repeated if: down rut (total rut) 9 mm and rut in HMA 2 mm: Use 45 mm HMA overlay, down rut 9 mm and rut in HMA < 2 mm: Use 75 mm HMA overlay Preservation-Preservation-Rehabilitation (PPR): Use if: down rut > 5 mm or cracking >0.25 m/m 2. Use 30 mm of HMA, RAC-G or MB4 overlay (with our without milling) down rut>5 mm and cracking > 0,25 m/m 2 Use 60 mm HMA overlay. after 2 preservation actions the next action will be treated as under rehabilitation, followed by 2 preservation, etc. 17

18 M&R Strategies M&R strategy EPP-HMA R-45 mm-rac-g R-75mm-HMA Action year M&R1 30 mm HMA Mill 30 mm RAC- G Mill 30 mm HMA Action year M&R2 Mill 30 mm HMA 45 mm RAC-G 75mm HMA Action year M&R3 Mill 30mm HMA 45 mm RAC-G Mill 30mm HMA Action year M&R4 Mill 30mm HMA Mill 30 mm RAC- G Mill 30mm HMA Action year M&R5 30mm HMA Mill 30 mm RAC- G Mill 30mm HMA Action year M&R6 30mm HMA 18 Note: 25 M&R strategies have been analyzed for this project

19 Evaluation of M&R Strategies Life-Cycle Cost Analysis TABLE 2: Summary of costs per Ln-Km for each M&R strategy Item type Thickness cost (mm) (1000 dollars per Ln-Km HMA Type A 30 mm 23 HMA Type A 45 mm 41 HMA Type A 60 mm 49 HMA Type A 75 mm 50 HMA Type A 105 mm 78 RAC-G 30 mm 27 RAC-G 45 mm 41 RAC-G 60 mm 54 MB4-D 30 mm 32 MB4-D 45 mm 48 MB4-D 60 mm 64 Cold plane 30mm HMA 30 mm 9 per m 2 AB Class mm 52 HMA Type A 160 mm

20 Evaluation of M&R Strategies Life-Cycle Cost Analysis TABLE 4: Annual Maintenance Cost calculation Annual Maintenance Cost ($/L-km) MC based on Action Yr 20 total Lane Km Total MC*1000 Year

21 Evaluation of M&R Strategies Life-Cycle Cost Analysis Type of Input Input Source of Input Criteria to select this input Value Economic Variable Value of Time for Passenger Cars ($/hour) RealCost Default Value Economic Variable Value of Time for Single Unit Trucks ($/hour) RealCost Default Value Economic Variable Value of Time for Combination Trucks ($/hour) RealCost Default Value Discount Rate (%) Discount Rate (%) LCCA manual [16] 3-5% range 4% Traffic Data AADT Construction Year (total for both directions) CalME AADT CalME AADT Traffic Data Cars as Percentage of AADT (%) CalME AADT CalME AADT 95 Traffic Data Single Unit Trucks as Percentage of AADT (%) CalME AADT CalME AADT 2.5 Traffic Data Combination Trucks as Percentage of AADT (%) CalME AADT CalME AADT 2.5 Traffic Data Annual Growth Rate of Traffic (%) default default 0.0 Traffic Data Speed Limit Under Normal Operating Conditions (mph) Hwy 53 HDM 55 Traffic Data No of Lanes in Each Direction During Normal Conditions considered 2 For research purpose 2 Traffic Data Free Flow Capacity (vphpl) LCCA manual,table6 Terrain, No. of Lanes 1950 Traffic Data Rural or Urban Hourly Traffic Distribution Hwy 53 Rural Rural Traffic Data Queue Dissipation Capacity (vphpl) LCCA manual,table6 Terrain, No. of Lanes 1530 Traffic Data Maximum AADT (total for both directions) LCCA manual,table6 Terrain, No. of Lanes 48305/lane Traffic Data Maximum Queue Length (miles) LCCA manual,table6 Terrain, No. of Lanes 5 Construction data Agency Construction Cost ($1000) Calculated Thickness, Lane miles 1316 Construction data Agency Maintenance Cost ($1000) LCCA manual 31 Construction data Work Zone Length (miles) default LCCA manual 2 Construction data Work Zone Speed Limit (mph) LCCA manual 5 miles less than original speed 50 Construction data Work Zone Capacity (vphpl) LCCA manual, Table 6 Terrain, No. of Lanes 1360 Construction data Work Zone Duration (days) LCCA manual Eq.4 lane miles/production rate 18 Construction data Production Rate LCCA manual, Table 8 surface type, daily closure 1.5 Construction data Activity service life (yrs) see def LCCA manual 1 Traffic Data Lane closure LCCA manual Inbound and outbound first closure 0 to 6 Traffic Data Lane closure LCCA manual Inbound and outbound second closure 20 to 24 21

22 EUAC Comparison EPP vs. R Strategies EUAC: EPP HMA (30mm) R-75 HMA Further analysis required to determine best strategy 22

23 Observations Cracking delayed in EPP-HMA (30mm) strategy. Earlier cracking in R-75 HMA (at year 25) can cause moisture ingress and subgrade and base problems. Hence, EPP-HMA considered best economical strategy. 23

24 Summary The major necessity and benefit of integrating ME and LCCA is to determine the best economical strategy for a given pavement segment and its application times. For the project analyzed Extended Pavement Preservation (EPP) was found to be the most economical strategy. Optimal strategy may differ from project to project. 24

25 Future Work Updating decision trees for the various M&R strategies in CalME. Caltrans current effort is to develop a more efficient PMS that will help in this work. The method presented is only for project-level optimization. Future work plans include extending its applicability to a network-level optimization. Incorporating LCCA module within CalME to provide a truly Hybrid System that will enable more efficient and speedy analysis. 25

26 Resources Training Fundamentals of Life Cycle Cost Analysis Live Instructor Led Distance Learning Course Onsite RealCost Life-Cycle Cost Analysis (LCCA) Software Workshop 26

27 Resources LCCA Primer FHWA-IF Technical Bulletin FHWA-SA LCCA Software RealCost 2.5 and User Manual 27

28 Thank you Tashia J. Clemons FHWA HQ Office of Asset Management 1200 New Jersey Ave SE Washington, DC