CT-RAMP Model Components ¶

Model Component Categories ¶

CT-RAMP components are organized into logical categories based on their role in the travel decision hierarchy:

Long-term and Coordination Models ¶

These models establish the context and constraints for daily travel decisions:

Tour Generation Models ¶

These models determine what tours each person will make:

Spatial Choice Models ¶

These models determine where travel occurs:

Modal Choice Models ¶

These models determine how travel occurs:

Temporal Choice Models ¶

These models determine when travel occurs:

Trip Detail Models ¶

These models add complexity and realism to travel patterns:

Model Execution Sequence ¶

The components execute in a carefully orchestrated sequence to ensure proper dependencies:

graph TD
    A[Auto Ownership] --> B[CDAP]
    B --> C[Mandatory Tours]
    B --> D[Joint Tours]
    C --> E[Individual Tours]
    D --> E
    E --> F[Tour Destination]
    F --> G[Tour Mode Choice]
    G --> H[Tour Time-of-Day]
    H --> I[Stop Frequency]
    I --> J[Stop Location]
    J --> K[Trip Mode Choice]
    C --> L[At-Work Subtours]

    subgraph "Phase 1: Context"
        A
        B
    end

    subgraph "Phase 2: Tour Generation"
        C
        D
        E
        L
    end

    subgraph "Phase 3: Tour Characteristics"
        F
        G
        H
    end

    subgraph "Phase 4: Trip Details"
        I
        J
        K
    end

    style A fill:#e3f2fd
    style B fill:#f3e5f5
    style F fill:#e8f5e8
    style K fill:#fff3e0

Model Dependencies and Data Flow ¶

Understanding how models depend on each other is crucial for system comprehension:

Data Dependencies ¶

• Auto Ownership requires: household demographics, accessibility measures
• CDAP requires: person characteristics, auto ownership results
• Tour Generation requires: CDAP patterns, person types, accessibility
• Tour Characteristics require: generated tours, level-of-service data
• Trip Details require: tour characteristics, stop purposes

Feedback Mechanisms ¶

Some models have iterative relationships:

Accessibility Feedback : Tour destination and mode choice results update accessibility measures

Household Coordination
: Joint decisions influence individual tour generation and characteristics

Capacity Constraints : Transit ridership affects level-of-service for subsequent iterations

Common Model Patterns ¶

All CT-RAMP components share common design patterns:

Choice Model Structure ¶

Most components use discrete choice models with these elements:

Alternative Generation : Define the set of available choices (destinations, modes, times, etc.)

Utility Calculation : Compute the attractiveness of each alternative using utility functions

Probability Calculation : Convert utilities to choice probabilities using logit formulations

Choice Selection : Select alternatives based on computed probabilities and random draws

UEC Integration ¶

Components use the Utility Expression Calculator (UEC) framework:

Utility Specifications : Mathematical expressions defining alternative attractiveness

Parameter Management : Organized storage and access to model coefficients

Logsum Calculation : Generation of accessibility measures for nested choice structures

Model Customization and Configuration ¶

Parameter Customization ¶

Each model component can be customized through:

Utility Function Parameters : Coefficients that control the importance of different factors

Alternative Set Definitions : Which choices are available in different contexts

Segmentation Schemes : How the population is divided for different model applications

Regional Adaptation ¶

Models can be adapted for different regions through:

Local Calibration : Parameter estimation using regional observed data

Alternative Specifications : Regional variations in available choices

Validation Standards : Local benchmarks for model performance

Component Documentation Structure ¶

Each component documentation page includes:

Model Overview ¶

• Purpose and role in the overall system
• Key behavioral assumptions and theory
• Relationship to other model components

Technical Specification ¶

• Model structure and choice alternatives
• Utility function specifications
• Parameter definitions and typical values

Data Requirements ¶

• Input data sources and formats
• Required preprocessing and validation
• Output data products and uses

Implementation Guidance ¶

• Configuration and setup procedures
• Calibration and validation approaches
• Common issues and troubleshooting

Examples and Use Cases ¶

• Practical applications and scenarios
• Analysis templates and workflows
• Interpretation guidance for results

Getting Started with Components ¶

For New Users ¶

1. Start with Auto Ownership - Foundation model that affects all others
2. Understand CDAP - Key to household coordination concepts
3. Follow the execution sequence - Work through models in dependency order

For Technical Users ¶

1. Review UEC specifications for each component
2. Understand coordination mechanisms for household interactions
3. Study integration patterns for system design

For Model Developers ¶

1. Examine utility functions for specification patterns
2. Review calibration procedures for parameter estimation
3. Study validation approaches for quality assurance

This overview provides the roadmap for understanding CT-RAMP’s comprehensive modeling system.

Last updated: September 26, 2025