Institutional Elements

Internal Changes  |  Performance Metrics  |  Model & Traffic Simulation

Institutional Needs

Institutional needs or requirements generally focus on strategic planning and on the organizations and people needed to execute those plans. They focus on how people and organizations are structured, funded, motivated, and informed. These requirements are based on the premise that active collaboration among people and organizations is the cornerstone on which an ICM effort is built. Stakeholders and expert frequently identify institutional requirements as the requirements most affecting the success of an ICM effort, which is why they are listed first. They include:

  • Maintaining and executing a corridor strategic plan for data collection, corridor control, and performance metric calculation
  • Ensuring that assets defined in the strategic plan are in existence
  • Maintaining project champions
  • Defining and implementing a solid management infrastructure, associated business processes, and corresponding knowledge, skills, and abilities (KSAs)
  • Ensuring all stakeholders are included and engaged in corridor decision-making and that these decisions are made within a culture of trust and communication
  • Ensuring required resources are committed to corridor day-to-day operations
  • Providing a properly skilled, educated, organized, trained, and motivated work force
  • Establishing and maintaining communications channels with all stakeholders and agencies throughout the life of the I-210 Pilot
  • Locating, securing, and monitoring funding opportunities
  • Ensuring sufficient funding is available for day-to-day operations
  • Managing Memoranda of Understanding and other agreements with stakeholders, organizations, agencies, and/or private companies and ensuring that they remain updated

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Caltrans Internal Changes for Corridor Management

A Caltrans project, Organizing for Corridor Operations, was conducted to identify institutional challenges related to ICM implementation. The project had six key deliverables: Corridor Management Work Plan, Corridor Performance Monitoring and Evaluation Work Plan, Corridor Performance Report Template, Statewide Planning for Operations - Recommended Updates to Planning and Guidance Document, Inventory of KSAs and Technical Assistance, and a Training Plan. The goal was to help Caltrans align the Division of Traffic Operations, especially in ICM pilot districts, with the principles of system management to maximize the performance of the existing and future transportation system. The project developed several optional organizational charts which were presented to District management, and revised to ultimately lead to a more detailed, preferred option.

The consultants developed four organizational options that were vetted with executive management, Operations Office Chiefs, Senior Operations staff, and the Strategic ICM Pilot Team. Ultimately, Option 4 was selected as the preferred option by staff at all levels. The preferred option builds from prior reorganization work done in the Caltrans districts of Traffic Operations to organize geographically and to assign staff to a new Corridor Manager position. The new organization provides for clear lines of reporting and supervision. The option is also scalable and can be deployed in small, manageable steps, a few corridors at a time. The option provides a logical path to the complete transition to a corridor management organizational structure.

corridor managment organizational chart

The option above was chosen because it most fully supports the move to a model that focuses on corridor and system management, and other Caltrans priorities. In addition to the recommended reorganization structure, an Implementation Plan was developed in coordination with District management and includes the following categories of activities:

  • Program Administration
  • Staff Recruitment and Template Development
  • Training and Staff Assignments

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Performance Metrics

At a minimum, key ICM performance measures should be identified in the following areas:

  • Mobility: Better people and freight movement
  • Reliability: More predictable corridor travel times
  • Safety: Fewer collisions, injuries, and fatalities; and less severity
  • Productivity: Fewer bottlenecks or hotspots that reduce flow rates
  • Emissions and Fuel Consumption: Reduced greenhouse gas emissions

The ability of the ICM system to produce corridor improvements satisfying all stakeholders depends on measuring project impacts using metrics to assess corridor operations. The selection of such metrics is a somewhat complex process, as different metrics are often used to manage freeways, arterial networks, transit systems, urban mobility, and environmental impacts. As an example, the table below lists metrics commonly used to evaluate specific operational dimensions of freeways, arterials, transit, and parking systems.

Ideally, a limited set of metrics should be used to evaluate different aspects of corridor operations. This will not only simplify data processing needs, but also facilitate the understanding of the decisions made by the ICM system. From this perspective, based on corridor stakeholder input and experiences gathered from other ICM implementations, the following base metrics are suggested for evaluating corridor performance:

Potential Corridor Metrics


Freeway Operations

Arterial Operations

Transit Operations

Parking Operations


Average travel Time


Average travel speed


Vehicle-hours of delay (VHD)


Person-hours of delay (PHD)


Average delay per vehicle


Average delay per person


Congested lane-miles



Level of Service (LOS)




Vehicle flow


Vehicle-miles traveled (VMT)


Vehicle-hours of travel (VHT)


Person flow


Person-miles traveled (PMT)


Person-hours of travel (PHT)


Flow density



Queue Length



Saturation flow rate



Vehicle flow capacity


Person flow capacity


Volume-to-capacity Ratio



Number of transit boarding/alighting




Parking availability




Parking utilization rate





Travel time index


Buffer index


Mean travel time


Median travel time


Nth percentile travel time


On-time performance





Number of accidents

Number of accidents with fatalities

Number of accidents with injuries

Frequency of accidents (per time period)

Frequency of accidents with fatalities

Frequency of accidents with injuries

Rate of accidents (per million VMT)

Rate of accidents with fatalities

Rate of accidents with injuries


Fuel consumption per vehicle


Fuel consumption per person


Emissions per vehicle


Emissions per person


 ●  Measure of primary interest     ○  Measure of secondary interest
  • Change in person-miles traveled (both on a nominal and percentage basis), to measure change in overall travel demand placed on the corridor when considering both roadways and transit services.
  • Change in person-hours of delay (both on a nominal and percentage basis), to measure improvement in corridor mobility.
  • Change in travel time reliability, to measure potential reduction in uncertainties associated with highly variable traffic conditions.
  • Reduction in the number and severity of secondary collisions (both on a nominal and percentage basis), to measure the safety benefits of the implemented corridor management strategies.

As indicated, using person-based metrics allows considering both increase/reduction in motorized traffic and increase/decrease in transit ridership, thus overall changes in travel demand. However, a potential problem with the use of person-based metrics is to know how many individuals are present in each vehicle (vehicle occupancy). While information about the number of occupants in each vehicle is typically unavailable, average values may be used for passenger cars and for transit operations based on historical data from relevant occupancy surveys. While using such values would not allow developing an exact operational assessment, no existing technology currently allows such an assessment to be made. While imperfect, using average vehicle occupancy thus provide a practical approach to consider the relative carrying capacity of passenger cars and transit vehicles in the current evaluation context. Vehicle-based evaluations would nevertheless remain possible by attributing the same occupancy value (i.e., a value of 1) to all vehicle types.

Whether additional metrics should be used, and how metrics should be combined to determine recommended response plans, is determined collectively by corridor stakeholders during the design phase of the ICM system.

The following are Performance Measure Targets from the ICMS Concept of Operations for a Generic Corridor produced by the FHWA:

Average Travel Time per Trip for the corridor and each network (includes long and short trips)  
  • Corridor – 20 minutes
  • Freeway HOV – 10 minutes
  • Freeway – 15 minutes
  • Arterials – 25 minutes
  • Rail – 20 minutes
  • Bus – 25 minutes
Average Delay per Trip for the corridor and each network
  • Corridor – 10 minutes
  • Freeway – 5 minutes
  • Arterials – 7 minutes
  • Rail – 5 minutes
  • Bus – 8 minutes


 Travel Time Index
  • Corridor daily vs. off peak – 1.2
  • Corridor Incident vs. peak – 1.3
  • Freeway daily vs. off peak – 1.1
  • Freeway incident vs. peak – 1.4
  • Arterials daily vs. off-peak – 1.3
  • Arterials incident vs. peak – 1.4
  • Rail daily vs. off peak – 1.0
  • Rail incident vs. peak – 1.4
  • Bus daily vs. off peak – 1.2
  • Bus arterial incident vs. peak – 1.4
 Buffer Index
  •  Corridor wide buffer index of 30 percent
 Average parking availability per facility per time of day
  • Zero average availability at end of peak period only 90 percent of the time
Customer satisfaction as obtained from traveler surveys
  • 80 percent overall satisfaction with corridor
  • 80 percent satisfaction with corridor traveler information and accuracy


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Corridor Model and Traffic Simulation

Model building is an iterative process that begins with the best data and best understood parts of the corridor and continues as additional data are analyzed and the model is expanded. 

The overall model-building process is illustrated in this figure:

overall model-building process diagram

As the figure shows:

  • Information about the corridor comes from various sources and different years and needs to be checked in a pre-processing step. Does it look reasonable (i.e., not garbled or fragmentary)? Is it fairly consistent? Does it seem usable for the intended purpose?
  • After the initial checks, the data is processed to produce the information needed for modeling and simulation, including:
    illustration of informaiton needed for modeling and simulation
  • Processed data is used to construct the model, a portion to calibrate the model, and a portion to validate the model’s simulation results against observed traffic conditions.
  • The completed model can be used to simulate traffic conditions along the corridor under various operational conditions, such as no incident, an incident with no intervention, and an incident with intervention.

The five primary purposes of the model are:

Pre-planning  To inform and validate the process of building incident response plans.
Real-time To score a response plan for use by the Decision Support System when the Pilot is deployed.
Retrospective To improve response plans and prediction capabilities and post-incident evaluations.
Special planning To inform other special planning needs.
Outreach and stakeholder support To visually demonstrate progress and build confidence.


A micro-simulation model is vital to any ICM project. The biggest limitation with model development is the available data, particularly data that can be used to determine flow patterns along arterials, such as where trips originate, which routes are taken, etc. New sensors will help fill critical gaps and the ISM team continues to work with stakeholders to ensure that all available existing sensors are functioning properly. Every bit of data helps and improves the reliability of the model.

The model is used to simulate traffic conditions and the results are compared with data from the field to determine its accuracy. Incidents and response plans are simulated to determine how a candidate action may affect traffic conditions. The model, and the predicted outcomes of the response plans, are currently being evaluated in close partnership with the stakeholders.

Corridor Re-Routes

Very early on in an ICM Pilot, the project team began designing corridor-wide response plans for incidents. What should a response plan do? What ITS infrastructure is needed to implement the response plans? How and when are decisions – in real time – which response plan to use? What approval mechanisms are needed and how do we know when to end a response plan?

Step one in the definition of response plans, is the identification of all potential preliminary alternate routes within the corridor. The list will undergo several iterations to refine the number of options and match them with available ITS element resources. The list is later refined to include all necessary alternate routes for all through routes in the corridor. Funding may be necessary to purchase and install the traffic signals, traffic sensors and the necessary changeable message signs needed to guide travelers along pre-agreed upon alternate arterial routes.  

A response plan is not limited to a traffic re-route. Signal and metering light timing changes, equipment and personnel requests, and communication plans could also be deployed as a part of a response plan. Stakeholders define all response plan components and when and where they will be used. Rules are then developed in the form of: “If an event occurs at location X, do Y and notify Z.” These rules are then processed by a rules engine, which evaluates many rules and determine the best response plan.

The rules engine must support a complex set of conditions to account for the complexity of incidents, considering factors such as time of day, day of the week, expected duration, location of the incident, and possible issues with alternate routes such as an active school zone. A response plan should also be scaled depending on the severity and length of the incident. For example, if two lanes of the freeway are expected to be closed for one hour, that would warrant a different response plan than if the two lanes were expected to be closed for ten hours or if the closure were to occur at 3am versus 3pm.

So how does a response plan get deployed? First, an incident must be identified and characterized with information such as its location, severity, and anticipated clearance time. For many projects, this will mostly be done by Caltrans TMC operators as they monitor the corridor 24/7. Information is then passed to the Decision Support System (DSS) which will use the rules engine to suggest one or more response plans. Simulation models are then used by the DSS to rank the possible response plans based on how much improvement each is likely to provide. Depending on the situation, the top response plan could then be automatically implemented or reviewed by transportation management staff who could either implement, modify, or reject the response plan. The time necessary to complete this process will vary according to how the entire system is designed and operated but should take less than 10 minutes from start to finish.

The response plans (include re-routes), DSS, and rules engine will need to be modified as needed for the life of the ICM project. New construction, transit service changes, or a number of other issues can impact the corridor and require updated response plans for the betterment of the corridor.


flow chart of role of rules engine


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