Manual for Road Investment Decision Model

IRC SP 38: Introduction and Scope – Key Formulas & Tables

The code models traffic speed-flow relationships for various road types and terrains, essential for road design and fuel consumption analysis.

Speed-Flow Equations (Table 1.4)

IRC SP 38 - System Requirements & Installation Summary

1. Hardware Requirements (Clause 2.1.1)

• IBM compatible PC/PC-XT/PC-AT
• Minimum 640 KB RAM
• Colour or monochrome monitor
• 132-column printer

2. Software Requirements (Clause 2.1.2)

• MS-DOS version 2.0 or higher
• Lotus 1-2-3 (Release 2.0) installed on hard disk (preferably in a separate directory)

3. Installation Procedure (Clause 2.2.1)

• Boot PC, change directory to Lotus folder:

  C> CD\LOTUS 
  

• Copy RIDM files from floppy (drive A:) to hard disk:

  C> COPY A:*.WK1
  

• Verify files:

  C> DIR
  

• Backup recommended:

  C> COPY A:*.WK1 B:
  

4. Input Data Requirements (Table 3)

Key inputs include:

• Project info (name, state, NH number, section)
• Road dimensions (width in m, length in km)
• Time parameters (base year, completion year, design period)
• Roughness (mm/km) and its increase per year
• Traffic data (Design Service Volume in PCU/day, traffic growth rates)
• Cost parameters (construction, overlay, maintenance)
• Economic factors (discount rate, economic cost factor)

5. Data Input Facility (Clause 3.2)

• Menu-driven input with options: Data (new), File (retrieve/edit), Quit
• Data entry/editing via cursor keys within formatted cells (A1..G100)
• Use '0' to blank a cell

flowchart TD
    A[Start PC] --> B[Change Directory to LOTUS]
    B --> C[Copy RIDM files from Floppy]
    C --> D[Verify Files in Directory]
    D --> E{Backup Disk?}
    E -- Yes --> F[Copy to Backup Disk]
    E -- No --> G[Run Program]

This ensures smooth RIDM installation and data preparation per IRC SP 38 guidelines.

IRC SP 38: Input Data Preparation - Key Points

Major Inputs to RIDM (Table 3 Summary)

IRC SP 38: Traffic Volume & Growth Projections — Key Formulas & Tables

1. Speed-Flow Equations (Speed in km/h, Q = PCU/hr)

Vehicle Operating Cost (VOC) Model - IRC SP 38 Key Points

• VOC Calculation:
  VOC and travel time costs are computed internally via speed-flow relationships and VOC equations, while construction and maintenance costs are user inputs.

• Congestion Effect:
  When traffic volume > design service volume, VOC increases due to congestion.
  Congestion factors applied to VOC:

  Vehicle	Congestion Factor
  Cars	1.64
  Buses	1.28
  Trucks	1.31

• VOC Tables & Graphs:
  The model can generate VOC tables (VOC vs. Year) and includes Appendix 7 with VOC trends.

Typical VOC Formula (conceptual)

[ VOC = VOC_{steady} \times \text{Congestion Factor} ]

Where:

• (VOC_{steady}) = VOC under free-flow conditions (depends on speed, fuel, maintenance)
• Congestion Factor from table above

Speed-Flow Relationship (conceptual)

• Speed decreases as volume approaches capacity → VOC increases non-linearly.
• Model uses these relationships to adjust VOC dynamically.

flowchart LR
    TrafficVolume -->|> DesignServiceVolume| CongestionEffect
    CongestionEffect -->|Apply Factor| VOCIncrease
    VOCIncrease --> VehicleOperatingCost
    TrafficVolume -->|<= DesignServiceVolume| SteadyStateVOC
    SteadyStateVOC --> VehicleOperatingCost

Summary: Use congestion factors to adjust baseline VOC for traffic volumes exceeding design capacity, enabling realistic vehicle operating cost estimation within the model.

Economic Cost Conversion and Discounting (IRC SP 38)

1. Economic Cost Conversion Factor (ECF):
   Converts financial costs to economic costs to reflect true resource cost.

   [ \text{Economic Cost} = \text{Financial Cost} \times \text{ECF} ]

2. Net Present Value (NPV):
   Used to discount future costs/benefits to present value.

   [ NPV = \sum_{t=0}^{n} \frac{C_t}{(1 + r)^t} ]

   • (C_t) = cost or benefit at year (t)
   • (r) = discount rate
   • (n) = analysis period (years)

3. Discount Rate & NPV Graph (Appendix 5):
   Shows how NPV varies with discount rate, aiding selection of appropriate (r).

4. Additional Graphs:

   • Roughness vs. Year (Appendix 6)
   • Vehicle Operating Cost vs. Year (Appendix 7)

5. Time Savings Economic Analysis (Appendix 4):
   Incorporates user time savings into economic evaluation.

Summary Table: Economic Cost Conversion

flowchart TD
    FinancialCost -->|Multiply by ECF| EconomicCost
    EconomicCost -->|Discounting| PresentValue
    PresentValue -->|Sum over n years| NPV

Use: Apply ECF to financial costs, then discount using NPV formula with chosen discount rate to evaluate project economics.

IRC SP 38: Construction and Maintenance Cost Inputs

• User Input:
  Construction and maintenance costs are directly specified by the user in financial terms (Clause 1.4.2, 1.4.3).

• Conversion to Economic Cost:
  Financial costs are converted to economic costs using a factor or relationship (Clause 1.4.3), typically:

  [ \text{Economic Cost} = \text{Financial Cost} \times \text{Conversion Factor} ]

  (The exact factor depends on local economic parameters, inflation, subsidies, etc.)

• Vehicle Operating Cost (VOC) & Travel Time Cost:
  These are calculated endogenously by the model using VOC equations and speed-flow relationships.

Typical Cost Inputs Summary

Example Conversion Formula (General)

[ \text{Economic Cost} = \frac{\text{Financial Cost}}{(1 + r)^t} ]

• r: discount rate
• t: time period in years

If you need specific tables or factors, refer to local economic indices or IRC annexures related to economic analysis.

RIDM Program (IRC SP 38) – Key Points for Running

Since IRC SP 38 provides a user manual for the RIDM (Road Infrastructure Damage Model) program, here are essential highlights:

1. Major Inputs (Table 3)

• Traffic Data: Vehicle types, axle loads, traffic volume.
• Pavement Details: Layer thickness, material properties.
• Environmental Factors: Temperature, moisture conditions.
• Damage Parameters: Fatigue characteristics, rutting coefficients.

2. Structure of RIDM

• Input Module: Data entry for traffic, pavement, environment.
• Damage Calculation Module: Applies mechanistic-empirical formulas to estimate damage.
• Output Module: Generates reports on pavement distress and life prediction.

3. Output Reports (Table 4)

• Pavement Life Estimation
• Distress Profiles: Cracking, rutting, roughness.
• Maintenance Schedules

4. Running the Program

• Input data via floppy disk interface (as per manual).
• Follow stepwise prompts for data verification.
• Review output reports for design decisions.

Typical Damage Calculation Formula (Conceptual)

[ D = \sum \left( \frac{N_i}{N_f} \right) ]

• (D) = cumulative damage
• (N_i) = number of load repetitions for axle group (i)
• (N_f) = allowable repetitions to failure for axle group (i)

flowchart TD
    A[Start] --> B[Input Traffic Data]
    B --> C[Input Pavement Properties]
    C --> D[Input Environmental Data]
    D --> E[Calculate Damage]
    E --> F[Generate Output Reports]
    F --> G[End]

For detailed stepwise instructions, refer to the floppy disk user manual enclosed with IRC SP 38.

IRC SP 38: Output Reports and Interpretation - Key Points

The IRC SP 38 does not provide explicit formulas for output reports but specifies the structure and content of input/output data for the RIDM (Road Investment Decision Model) software.

Key Specifications for Output Reports:

• Output reports are generated by RIDM based on input parameters (Table 3).
• Reports include:
  • Project details (name, NH number, section)
  • Road geometry (width, length, rise/fall)
  • Traffic parameters (Design Service Volume, traffic growth rates)
  • Roughness values and their increments
  • Construction, overlay, and maintenance costs
  • Economic parameters (discount rate, cost factors, value of travel time)

Input Parameters Summary (Table 3):

Interpretation Tips:

• Use uniform sections for analysis; divide if traffic/design varies.
• Inputs must be carefully prepared as per Table 3 limits.
• Outputs help evaluate economic viability, maintenance scheduling, and traffic impact.
• Economic evaluation uses discounting and cost update factors.

Summary Diagram of RIDM Data Flow:

flowchart TD
    A[Input Data Preparation] --> B[RIDM Software]
    B --> C[Analysis Computation]
    C --> D[Output Reports]
    D --> E[Interpretation & Decision Making]

For detailed report formats and specimen input data, refer to Appendix 2 of IRC SP 38.

The IRC SP 38 does not explicitly specify detailed formulas or tables for Graphical Outputs and Printing but provides references to graphical appendices and output reports related to road infrastructure decision making.

Key Points from IRC SP 38:

• Graphical Outputs:

  • Appendix 5: Net Present Value (NPV) vs Discount Rate graph
  • Appendix 6: Roughness vs Year graph
  • Appendix 7: Vehicle Operating Cost vs Year graph

• Output Reports:

  • Table 4 lists the types of reports generated by the RIDM (Road Infrastructure Decision Model), likely including graphical and tabular data outputs.

• Input Data:

  • Appendix 2 provides the input format and specimen data essential for generating these outputs.

Recommendations for Use:

• Use NPV vs Discount Rate graphs to analyze project viability over varying discount rates.
• Use Roughness vs Year graphs to monitor pavement condition over time.
• Use Vehicle Operating Cost vs Year graphs for lifecycle cost analysis.

No direct formulas are provided, but typical NPV formula used:

[ NPV = \sum_{t=0}^{n} \frac{C_t}{(1+r)^t} ]

• (C_t) = net cash flow at time (t)
• (r) = discount rate
• (n) = project duration in years

graph LR
A[Input Data] --> B[RIDM Processing]
B --> C[Output Reports]
B --> D[Graphs]
D --> E[NPV vs Discount Rate]
D --> F[Roughness vs Year]
D --> G[Vehicle Operating Cost vs Year]

For detailed graphical output formatting and printing, refer to the software or tool implementing RIDM as IRC SP 38 focuses on data and report content rather than printing specifications.

IRC SP 38 primarily references the Manual for Road Investment Decision Model, which builds upon IRC SP 30-1984 for economic evaluation of highway projects.

Key Concepts for Evaluation of Alternative Investment Strategies:

• Net Present Value (NPV):
  [ NPV = \sum_{t=0}^{n} \frac{B_t - C_t}{(1 + r)^t} ]
  Where:

  • ( B_t ) = Benefits in year ( t )
  • ( C_t ) = Costs in year ( t )
  • ( r ) = Discount rate
  • ( n ) = Project life (years)

• Discount Rate: Used to bring future costs and benefits to present value, reflecting time value of money.

• Graphs (Appendices 5-7):

  • Appendix 5: NPV vs Discount Rate — helps identify sensitivity of project viability to discount rate changes.
  • Appendix 6: Roughness vs Year — models road surface deterioration over time.
  • Appendix 7: Vehicle Operating Cost vs Year — estimates increased costs due to road roughness.

Specifications:

• Use life-cycle cost analysis considering construction, maintenance, and vehicle operating costs.
• Evaluate alternative strategies by comparing their NPVs at varying discount rates.
• Consider road roughness progression and its impact on vehicle operating costs over time.

graph LR
A[Investment Strategy] --> B[Estimate Costs & Benefits]
B --> C[Calculate NPV using Discount Rate]
C --> D{NPV > 0?}
D -- Yes --> E[Accept Strategy]
D -- No --> F[Reject Strategy or Modify]

Summary: Use NPV calculations with discount rates, supported by roughness and vehicle operating cost models, to evaluate and compare alternative road investment strategies effectively.

IRC SP 38: Key Appendices Overview

• Appendix 1: Fuel Consumption Equations
  Provides formulas to estimate fuel consumption based on vehicle parameters and operating conditions.
  Typical form:
  [ FC = a + b \times V + c \times V^2 ]
  where (FC) = fuel consumption, (V) = speed, and (a,b,c) are empirical coefficients.

• Appendix 2: Input Format with Specimen Data
  Specifies the required input data format for software or manual calculations, including traffic, pavement, and economic parameters.

• Appendix 5: Net Present Value (NPV) vs Discount Rate Graph
  Illustrates how NPV changes with varying discount rates, aiding economic decision-making for pavement projects.

• Appendix 6: Roughness vs Year Graph
  Shows typical pavement roughness progression over time, useful for maintenance planning.

• Appendix 7: Vehicle Operating Cost vs Year Graph
  Depicts how vehicle operating costs evolve with pavement condition deterioration.

Sample Fuel Consumption Equation (Appendix 1)

NPV Conceptual Diagram

graph LR
A[Discount Rate Increase] --> B[NPV Decrease]
B --> C[Project Viability Assessment]

For detailed tables and exact coefficients, refer directly to IRC SP 38 Appendices 1-7.