Traffic Studies for Planning Bypasses Around Towns

IRC 102 - Scope: Key Formulas, Tables, and Specifications

1. Speed-Volume Relationship

• Estimated Speed (Vest):
  [ V_{est} = V_y - KQ ]
  • (V_{est}) = Estimated speed (km/h)
  • (V_y) = Average free speed (km/h)
  • (K) = Coefficient
  • (Q) = Average hourly traffic volume (vehicles/hr)

2. Key Forms for Traffic Analysis

• Form 8: Analysis of observed and estimated travel speeds, delays, and volumes.
• Form 9: Origin-Destination survey - route-wise through traffic counts by vehicle type.
• Form 10: Economic losses due to delays, fuel consumption, and manhours lost.
• Form 11: Direct economic losses summary (manhours and fuel costs).
• Form 12: Projected economic losses over a 20-year design period.

3. Important Tables

4. Specifications

• Sample sizes in surveys must be expanded proportionally to traffic counts.
• Bypassable traffic percentage is critical for planning urban bypasses.
• Economic loss calculations include manhours lost and extra fuel consumption due to delays.

flowchart LR
    A[Traffic Volume Q] --> B[Speed-Volume Relationship]
    B --> C[Estimated Speed Vest]
    C --> D[Travel Time & Delay Analysis]
    D --> E[Economic Loss Calculations]
    E --> F[Project Planning & Bypass Justification]

This scope covers traffic performance evaluation and economic impact assessment essential for urban arterial and bypass planning under IRC 102.

IRC 102: Classification of Traffic – Key Points

1. Vehicle-wise Traffic Breakup (Form 9)

Traffic is classified by vehicle type and time period:

2. Speed-Volume Relationship (Clause 20.00, Form 8)

[ V_{est} = V_t - K \times Q ]

• (V_{est}) = Estimated speed (km/h)
• (V_t) = Average free speed (km/h)
• (K) = Coefficient (depends on road/traffic conditions)
• (Q) = Average hourly traffic volume (vehicles/hour)

3. Parameters to Analyze (Form 8)

• Average hourly traffic volume (veh/hr)
• Average travel time (minutes)
• Average travel speed (kmph)
• Average free speed (kmph)
• Average travel time at free speed (minutes)
• Average delay (minutes)

4. Traffic Count Analysis

• Hourly volumes are tabulated (Form 4)
• Used to estimate traffic composition and flow characteristics

This classification aids in designing road capacity, traffic management, and safety analysis by distinguishing vehicle types and their impact on traffic flow.

IRC 102: Origin and Destination Survey - Key Points

The IRC 102 provides guidelines for conducting Origin and Destination (O-D) surveys to analyze travel patterns.

Key Methods & Forms:

• FORM 1: Traffic Counts
  • Collects volume data at key points to estimate trip generation.
• FORM 2: Roadside Interview Method
  • Interviews travelers to record trip origins, destinations, purpose, and mode.
• FORM 3: Travel Time and Delay Studies
  • Measures travel time and delays on selected routes to assess traffic flow.

Important Specifications:

• Sampling:
  • Select representative locations and times to capture typical traffic patterns.
• Data Collection:
  • Use manual or automated counters for FORM 1.
  • Structured questionnaires for FORM 2.
  • Stopwatch and GPS tools for FORM 3.
• Data Analysis:
  • Trip matrices derived from FORM 2.
  • Average travel speeds and delays from FORM 3.

Typical O-D Matrix Format:

flowchart LR
    A[Traffic Counts (FORM 1)] --> B[Trip Volume Data]
    C[Roadside Interviews (FORM 2)] --> D[Trip Origin-Destination Matrix]
    E[Travel Time & Delay (FORM 3)] --> F[Travel Time & Delay Analysis]
    B --> G[Trip Generation & Distribution]
    D --> G
    F --> G

This integrated approach ensures comprehensive travel demand analysis per IRC 102.

Travel Time and Delay Studies (IRC 102)

Key Formulas:

• Estimated Speed (Vest):
  [ V_{est} = V_t - K \times Q ]

  • (V_t) = Average free speed (km/h)
  • (K) = Coefficient (depends on road conditions)
  • (Q) = Average hourly traffic volume (veh/hr)

• Average Delay (mins):
  [ \text{Delay} = \text{Average travel time at observed speed} - \text{Travel time at free speed} ]

Important Tables (Form 8):

Route-wise Traffic Analysis (Form 9):

• Break down traffic by vehicle type (trucks, buses, cars, two-wheelers) and time periods (e.g., 8-12, 12-16 hrs).
• Helps identify peak delay periods and traffic composition.

flowchart TD
    A[Traffic Volume Q] --> B[Calculate Estimated Speed Vest]
    B --> C[Calculate Travel Time at Vest]
    D[Free Speed Vt] --> E[Calculate Travel Time at Free Speed]
    C --> F[Calculate Delay = Travel Time Vest - Travel Time Free Speed]

This framework aids in assessing congestion and planning improvements.

IRC 102: Analysis and Projection - Key Points

1. Projection Formula (Traffic Growth)

• Future traffic ( P ) is projected based on base year traffic and growth rate (not explicitly given here, typically exponential or compound growth):

  [ P = P_0 \times (1 + g)^n ]

  where:

  • ( P_0 ) = current traffic volume,
  • ( g ) = annual growth rate,
  • ( n ) = number of years ahead.

2. Economic Losses Table (Table E-12)

• Shows direct economic losses (lakh rupees) for through and local traffic over 20 years.
• Losses increase with traffic volume, used for cost-benefit and design year analysis.

3. Vehicle Economic Values (per IRC:SP:30)

• Car/Scooter = Rs 16
• Bus = Rs 9
• Truck = Rs 3.8
• Cycle/Animal Drawn Vehicle = Rs 2.5

4. Speed-Volume Relationship (Clause 20.00, FORM 8)

• Estimated speed ( V_{est} ) formula:

  [ V_{est} = V_f - K \times Q ]

  where:

  • ( V_f ) = average free speed (km/h),
  • ( K ) = coefficient,
  • ( Q ) = average hourly traffic volume (veh/hr).

• Used to estimate delays and travel times for traffic analysis.

5. Analysis Tools

• **Form 8

IRC 102 — Presentation of Traffic Data: Key Formulas & Tables

Key Formula: Estimated Speed from Volume

[ V_{est} = V_t - K \times Q ]

• (V_{est}) = Estimated speed (km/h)
• (V_t) = Average free speed (km/h)
• (K) = Coefficient (depends on road conditions)
• (Q) = Average hourly traffic volume (vehicles/hr)

Important Tables for Data Presentation

Data Presentation Tips

• Use hourly intervals for delay/run time data.
• Summarize vehicle counts by category and time period.
• Calculate delays and speeds using the formula above.
• Present percentages for bypassable traffic to identify congestion relief potential.

flowchart TD
    A[Traffic Volume Q] --> B[Calculate Estimated Speed V_est]
    B --> C{Compare with Free Speed V_t}
    C -->|V_est < V_t| D[Calculate Delay]
    C -->|V_est ≈ V_t

IRC 102 Example Case Study: Key Formulas & Tables

1. Traffic Delay & Speed Analysis (Form 8)

• Estimated Speed Formula:

[ V_{est} = V_f - K \times Q ]

Where:

• (V_{est}) = estimated speed (km/h)

• (V_f) = average free speed (km/h)

• (K) = coefficient (depends on road conditions)

• (Q) = average hourly traffic volume (vehicles/hr)

• Average Delay:

[ \text{Average delay} = \text{Average travel time} - \text{Travel time at free speed} ]

2. Origin-Destination Matrix (Table E-1)

• Shows vehicle flows between zones on the arterial road, essential for identifying through vs local traffic.

3. Losses in Manhours & Fuel (Form 10)

4. Economic Loss Assessment (Form 11 & 12)

5. Case Study Summary (Clause 7)

• Urban arterial divided into sections; traffic counts and delays analyzed.
• Origin-Destination surveys identify bypassable traffic.
• Economic losses calculated to justify bypass planning.
• Tables E-4 to E-12 provide detailed data analysis for decision-making.