Department of Transportation: Federal Highway Administration
Table of Contents

Integrated Corridor Management Initiative – ICMS Surveillance and Detection Needs Analysis for the Transit Data Gap

2.0 ICM and ICMS Context

This document is an analysis of transit data which is needed to support an ICMS corridor. A basic understanding of the ICM concept and an ICMS is necessary in order to adequately analyze the transit data requirements. This section provides a description of the ICM and ICMS Context.

2.1    ICM Context

ICM is based on four concepts:

  1. Corridor modes of operation
  2. Strategic areas for ICM
  3. Conceptual levels within the corridor
  4. ICM environment

2.1.1  Corridor Modes of Operation

The corridor mode of operation refers to the manner in which the corridor ICM manager and/or the transportation network operators are operating the transportation networks that comprise a corridor. There are two major corridor modes:

  1. Normal mode which constitutes all the actions taken to ensure that day-to-day transportation needs are addressed.
  2. Event mode which consists of two sub-modes
    • Planned event mode:  an event that is known prior to the occurrence which will reduce the existing corridor capacity.
    • Unplanned event mode:  an event which increases demand on a corridor network without foreknowledge.

A corridor can be shifted between normal mode and event mode several times during a day or can operate in a single mode for the entire day. In order to shift modes, the corridor manager has to assess the event severity, the impact on the entire corridor, and the expected duration of an event before shifting from normal mode to event mode. The ability of the existing systems to support the shift must also be analyzed.

2.1.2  Strategic Areas for ICM

In order to manage the corridor in an integrated fashion requires the corridor manager to develop strategies in four areas and implement those strategies. The four strategic areas are:

  1. Demand management:  addresses the patterns of usage of the transportation networks
  2. Load balancing:  addresses operating each network to its maximum effectiveness
  3. Event response:  addresses the response to events based on their duration
  4. Capital improvement:  addresses the need for improvements to corridor facilities

Control strategies can be developed within the first three strategic areas establishing actions to implement the strategy. Within the fourth strategic area, recommendations for capital expenditures for facility improvements are developed.

2.1.3  Conceptual Levels within the Corridor

There are three distinct conceptual levels within a corridor. These are:

  1. The physical level which includes all field components.
  2. The information and sharing level which provides the tools and information systems that take the data from devices and transform the data into information that the transportation system operators can use to make operational decisions about the transportation networks.
  3. The executive or decision-making level which includes the people who make the decisions and the plans, actions, on-the-spot decisions, and controls needed to operate the transportation systems within the corridor.

2.1.4  ICM Environment

The ICM environment consists of the four strategic areas resting upon the three conceptual levels.

2.2    ICMS Context

An ICMS is a tool to help optimize corridor operations. While it is not possible to keep networks operating optimally all the time, continuous optimization is the overall goal. There are two major aspects in the discussion of an ICMS:

  1. Operational needs
  2. System architecture

2.2.1  Operational Needs

The ICMS operational needs represent a high-level statement of the capabilities required to implement and operate an ICMS. A generic set of ICMS needs are summarized in Appendix C.

A corridor may be comprised of several transportation modes that collectively move goods and people through the corridor. Within the ICM Initiative, a corridor is recognized if it includes at least three of the following transportation modes:

  1. Freeway roadway network
  2. Arterial roadway network
  3. Bus transit network
  4. Rail transit network
  5. Toll roadway network
  6. Ferry network

The goal of the ICMS is to optimize the use of the transportation resources across all modes of transportation within the corridor. Optimization implies a regulating process that measures performance of a system and modifies the control parameters governing operation of the system in ways that will improve or maintain the performance of the system. This is a simple feedback loop.

In a feedback driven control system, positive feedback tells the system to increase the output value. Negative feedback tells the system to reduce the output value. Optimization is achieved when feedback has driven each control parameter to a state that results in the best possible performance of the system (as described by the performance measures monitored within the system).

Optimization therefore implies:

  1. The desired performance of the system can be described based on measurable outputs of the system.
  2. Performance of the system can be controlled using control measures or strategies that both positively and negatively change the performance of the system.

Figure 1 – Simple Feedback Optimization

figure 1 - diagram - This figure shows the simple feedback optimization control system.

If a control system automatically uses performance feedback to regulate a system, the controls are considered to be a “closed loop” system. If a control system provides performance feedback information to a human, who must then take action to change the control measures, the system is considered to be an “open loop” system. Complex control systems may use a combination of open and closed loop controls for each control parameter.

Figure 2 – Multiple Result Optimization

figure 2 - diagram - This figure shows the multiple result optimization control system.

Optimization of multiple transportation modes requires a control feedback loop for each transportation mode. If performance of one transportation mode can impact the performance of other transportation modes (and they almost always do), then the feedback must be based on the performance of both systems. There must be a way of describing the value of the desired performance of each system in terms that are common between the systems. Hence, it is acceptable to improve the performance of one system if the change increases the total performance value of all of the inter-related systems, but not acceptable if the total performance value is decreased. Improving the performance of one mode of transportation at the expense of performance of another mode is only acceptable if the Total Net Value of the change is positive. Improving freeway performance by one dollar at the expense of a two dollar decrease in transit or arterial performance is not acceptable. This establishes a third constraint on optimization which applies when there are two or more performance goals that must be optimized by the same system:

  1. If two or more outputs are to be optimized, the governing feedback must be based on both outputs, the value of the results must be expressed in common terms, and the governing feedback must be applied to the inputs for all of the controlled systems.

2.2.2  System Architecture

An ICMS typically has three distinct functions that establish how it will work:

  1. Input – Information about the current situation or problem to be solved.
  2. Processing – The rules or algorithms that establish what the system should do given the states of the inputs.
  3. Output – The results of the processing based on the inputs and processing algorithms.

Note that the architecture does not depend on the number or type of inputs, nor on the number of computers that might be required for processing or where the computers might be located. This means that an ICMS can be a centralized or distributed system, closed loop control, open loop control, or a hybrid of both closed and open loop controls.

The ICMS architecture is constrained by the primary goal of optimizing the movement of goods and people through the corridor using the available transportation modes. From the previous section, it is evident that the ICMS must receive inputs in the form of information and operational decisions from every participating transportation mode in the corridor. The ICMS processing algorithms must be capable of determining what should be done based on all of the possible states of all participating transportation modes. The ICMS outputs must be based on optimizing the value of the performance of all of the travel modes to the stated goal of moving goods and people through the corridor.

Simple integration of communications and computing infrastructure will not be sufficient for an ICMS architecture. Sharing information and ITS equipment controls will not constitute an ICMS. An ICMS architecture will require AMS components capable of evaluating multiple travel modes, and decision support or closed loop control components capable of using feedback from the AMS components to make changes in how all of the transportation modes operate. An ICMS requires a common understanding and agreement across all corridor participants as to how “good for the corridor” will be measured. A system where participants will only make changes that benefit the operation of their particular transportation mode is not truly integrated, nor can it be considered an “Integrated Corridor Management” system.

2.2.3  Gap Analysis Context

The preceding sections establish a context for this gap analysis. The analysis is not about data for surveillance and detection for daily operations and record keeping. Often, more baseline information is required for modeling than for daily operations. Modeling and decision support for transit network optimization will require a finer granularity of data than what is needed for simple operational purposes.

This analysis will focus on:

  1. performance measures for transit management and the data required to calculate these performance measures;
  2. data required for AMS systems to evaluate corridor performance relating to transit systems;
  3. data required to assess the impact of strategies and corridor control measures on the performance of transit systems; and
  4. data acquisition capabilities which are currently available for monitoring transit systems.
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