Transportation Systems Analysis and Modeling: A Comprehensive Guide
Aspects to Consider When Designing a Model
Purpose
Define the objective of building the model.
Variables
Identify controllable and relevant variables.
Level of Aggregation
Determine the appropriate level of detail.
Time Horizon
Specify the study’s time frame and whether a dynamic model is necessary.
Techniques
Select suitable statistical and mathematical methods.
Calibration and Validation
Establish methods for model calibration and validation.
Underlying Theory
Clarify the theoretical foundation of the model.
What is an Origin-Destination Matrix?
An origin-destination matrix represents traffic flow, showing the number of trips between different area pairs.
The Challenge of Transportation Systems Analysis
According to Manheim (1977), the challenge lies in strategically intervening in society to effectively utilize the transportation system, coordinating public and private actions to achieve societal goals.
Smith’s Theory of Route Choice
Smith posits that network users change routes only if the total operational cost, calculated based on observed costs before the change, decreases.
Discrete Choice Models
Discrete choice models, also known as qualitative choice models, are useful for modeling individual choices characterized by:
- A finite set of alternatives
- Mutually exclusive alternatives
- Exhaustive alternatives (all available options are included)
Underlying Assumption
The underlying assumption is that the probability of an individual choosing a particular alternative depends on individual characteristics and the relative attractiveness of each option.
Components of a Transportation System (T)
- C: Conveyor
- I: Infrastructure
- V: Vehicles
- O: Operation (or Management)
Factors Influencing Transportation (A)
- System Activities
- Population
- Land Use
- Employment and Production
Flow Structure (F)
- Origins and Destinations
- Routes
- Volumes
Interactions within the Transportation System
- F = T * A: Flow (F) is a product of interactions between the Transportation System (T) and influencing factors (A).
- F → A: Flow (F) causes long-term changes in factors (A) through service patterns and resource consumption.
- F → T: Observed flow (F) over time leads to changes in the Transportation System (T), such as new services or modifications to existing ones.
Equilibrium in Transportation Systems
Relationship 1 involves short-term equilibrium (travel market), while relationship 2 involves long-term equilibrium, balancing changes in activity systems caused by changes in flow structure (F).
Transport System (T) Options
Technological Options
Examples: Air or sea transport
Topological Options
General settings (nodes, links), geographical location, network types.
Connection Options
Adding links, increasing capacity, multimodal networks (e.g., metro-train, metro-bus).
Fleet Options
Number and size of vehicles.
Operation Policy Options
Itineraries, prices, and regulations.
Organizational Policy Options
How to organize the transport sector (e.g., SPECTRA).
Interacting Entities in Transport System Options
- Users (Passengers and Shippers): Decide whether, when, where, and how to travel or ship.
- Operators: Provide services, routes, frequencies, rates, and vehicle types.
- Government: Plays a crucial role in regulation, subsidies, and taxes, influencing decisions of users and operators.
What is a Model?
A model is a representation of reality, an abstraction used to gain conceptual clarity by reducing complexity to analyzable levels.
What is a Metro?
A metro (underground, subway) is a mass transit rail system in large cities, connecting various parts of the urban area and surroundings with high capacity and frequency, separated from other transport systems.
Microsimulation Models
Microsimulation models are primarily governed by car-following models, describing the interaction between two vehicles in a lane. A common formula is f = F(vl, vf, s, dl, df, Rf, di), assuming a correlation between vehicles within an inter-vehicle distance of 0 to 125 meters.
Tasks Involved in Driving
- Perception: Gathering information through the driver’s visual channel, especially regarding the movement of the vehicle ahead.
- Decision-Making: Making decisions based on perception, influenced by driving skills and experience.
- Control: Performing maneuvers using feedback from perception and decision-making.
The precise way drivers perform these functions remains unclear, and there’s no single transfer function to describe driver behavior.