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21st Century Operations Using 21st Century Technologies

Incorporating Travel-Time Reliability into the Congestion Management Process (CMP): A Primer

Chapter 4. Model Congestion Management Plan

This chapter provides a model Congestion Management Plan (CMP) that demonstrates how reliability can be incorporated at appropriate steps. Addressing reliability and non-recurring congestion enhances and expands upon the current state of the practice for most CMPs. The model CMP is not intended to be a complete document; it is an assembly of excerpts intended to provide insight for metropolitan planning organization (MPO) developers of CMPs.

4.1 One Size Does Not Fit All

Each MPO operates in a unique circumstance, so this model CMP should be used as guidance and be considered in relation to your region's population, funding, governance, transportation system priorities, data availability, and staff capacity. Even if your MPO does not assign a high priority to congestion mitigation, or has a modest level of recurring congestion, the public and their elected officials may be supportive of improving the reliability of travel time by addressing non-recurring congestion.

4.2 Model Plan Excerpts

The following section shows examples of the different CMP components and how reliability can be integrated.

This section covers:

  • Goals and Objectives
  • Performance Measures
  • Monitoring Plan
  • Problem Identification
  • Identification of Strategies
  • Implementing Strategies and Monitoring Strategy Effectiveness

Goals and Objectives

Establishing goals and objectives is the first substantive step in the CMP and a key entry point for consideration of reliability.

MPOs enumerate their goals and objectives in the metropolitan transportation plan (MTP), including decisions on how to treat congestion mitigation and non-recurring congestion. The CMP should incorporate these goals and objectives, rather than create a new set of priorities.

The following excerpt from the Binghamton (NY) Metropolitan Transportation Study's 2035 Plan [13] is an example that gives priority to operational solutions:

The North Central Texas Council of Governments in Dallas-Fort Worth demonstrates how a goal from the MTP related to system operations can lead to objectives for improving operations and reliability can be translated into the CMP [14]:

Performance Measures

Objectives are supported by performance measures that are used to track and demonstrate outcomes of projects and actions that are designed to improve reliability.

Moving Ahead for Progress in the 21st Century Act (MAP-21) establishes a paradigm of performance-based planning and programming (PBPP) for MPOs, transit operators, and state departments of transportation (DOTs). They will be required to be accountable for their investment decisions by measuring the results of project and programmatic actions. Performance measures must be credible and easily understood by the public and MPO decision-makers. "Did the money we spent on the Enhanced Incident Management Program improve travel-time reliability as much as we forecasted?" Below is an example from the Delaware Valley Regional Planning Commission in Philadelphia, emphasis added, where speed drop duration was analyzed over time to identify periods of non-recurring congestion.

The Madison Transportation Planning Board's CMP [15] proposes a larger set of performance measures related to reliability. The existing measures highlight causes of non-recurring congestion, and therefore are only secondary indicators of reliability. The preferred measures, to be developed, are a more direct metric. Because the CMP is a continuous process, it is acceptable to define measures that can be developed to improve understanding of outcomes. In this case, the MPO shows the resource requirements in terms of capital funding and human effort for the proposed measures, summarized below in Table 11 from page 40 of their CMP.

Monitoring Plan

A performance based, outcome-oriented CMP must include a plan to monitor the transportation system and report on improvements to travel-time reliability.

Performance measurement is a continuous process. This is especially true for assessing impacts on reliability, where the basis is measuring variability over time. The CMP may include a monitoring plan that enumerates for each performance measure the agency that is responsible for data collection, analysis, and archiving; how often the measure will be updated; and how it will be reported.

Table 2 on Page 7 of the Madison (WI) Transportation Planning Board's CMP [15] demonstrates how this could be formulated.

Problem Identification

This step of the CMP provides the MPO an opportunity to identify reliability problems related to non-recurring congestion, based on their adopted performance measures.

This example shows how reliability is incorporated into the problem identification stage of the process. This example is from the Durham-Chapel Hill-Carrboro Metropolitan Planning Organization, emphasis added.

Identification of Strategies

In this step, the MPO specifies the project, actions, and strategies it intends to undertake to improve reliability.

The following excerpt from page 48 of the Genesee Transportation Council (Rochester NY) CMP [16] is a list of strategies for improving freeway operations, which should lead to improved reliability.

2. Urban Freeways Operations

2.A. Incident Management

Definition: Incident management involves the coordination of three stages: detection/verification; response/clearance; recovery/information. The aim of incident management should be to quickly and efficiently clear incident scenes without endangering first responders or the traveling public. This returns the roadway to normal operations sooner and reduces the likelihood of secondary incidents. Many incidents are vehicle disablements that can be quickly cleared.

Congestion Mitigation Impacts: Reduced incident-related delay; fewer secondary incidents.

2.B. Highway Information Systems

Definition: Communicate dynamic information regarding existing traffic conditions to travelers en-route on the transportation system. These capabilities include technologies such as Dynamic/Variable Message Signs (DMS/VMS), Highway Advisory Radio (HAR), and in-vehicle/handheld systems such as Geographic Positioning Systems (GPS) and personal travel assistants.

Congestion Mitigation Impacts: Reduced speeds of vehicles nearing queues (fewer secondary crashes); diversion to alternate routes/modes.

2.C. Ramp Metering

Definition: Ramp meters are modified traffic signals placed at the end of highway entrance ramps. This controls the flow of vehicles onto highways by breaking up platoons of vehicles attempting to enter the highway, thus streamlining the merge process. Delays may be incurred for ramp traffic, but mainline capacities are protected and overall operational efficiency is improved.

Congestion Mitigation Impacts: Increased freeway capacity; reduced short freeway trips; increased volume/capacity ratio on highways; decreased crash rate.

2.D. Highway Pricing Strategies

Definition: Levy fees for driving during peak travel times or under congested conditions. Place a surcharge on parking in congested areas. Use electronic toll collection systems to ease congestion at toll booths.

Congestion Mitigation Impacts: Diversion to alternate routes; mode switches; destination changes; increased trip chaining.

2.E. Road Work Zone Management

Definition: Manage road work zones to mitigate their impact on traffic. Limit work activities to off-peak travel hours; phase work activities on a daily, weekly, or seasonal basis to minimize traffic impacts; conduct a public awareness program in advance of road work; identify and promote alternate routes; promote ridesharing or transit use.

Congestion Mitigation Impacts: Improved throughput around road work zones; minimized vehicle delays and speed reductions; reduced crash rate.

Source: Genesee Transportation Council CMP (2013), Page 48

Implementation Strategies and Monitoring Strategy Effectiveness

The ultimate purpose of the CMP is to create a rational approach to mitigating congestion. The policy board can weigh the highest priority CMP projects and strategies against other needs when the MPO develops its transportation improvement program (TIP)

The following shows how reliability strategies can be implemented and monitored to assess effectiveness. This example is from the Durham-Chapel Hill-Carrboro MPO (emphasis added).

Chapter 8 - Implementing Strategies and Monitoring Strategy Effectiveness

The previously identified improvement strategies should be incorporated into the regional transportation plan and the TIP. The implementation processes of the defined strategies will be closely monitored if the improvements are adopted in the TIP or other program with the financial commitment. The implementation of the improvement strategies will be led by the operating agencies, and the progress should be reported to the MPO every month.

The implemented strategies will be monitored to assess their effectiveness. Monitoring techniques and schedules will be dependent on the type of improvement that is implemented, and the data availability. It may take years to assess the benefits of safety-type improvements that are intended to reduce crash rates, crash severity, or incidents. Conversely, the benefits of capacity improvements are relatively easy to measure and assess. Travel time reliability improvements will be monitored via the existing data collection methods within the region.

The benefits of the implemented strategies will be documented in the biannual report. For the improvements that may not be accurately measured in a two year time frame, results will be presented with a description of the limitations of monitoring. Capacity projects and other improvements that are implemented through non CMP methods will still be monitored to determine their benefits. Based upon the monitoring results, the learned facts will provide feedback for the CMP to verify and update the used performance measures, the applied data analysis techniques, and the considered strategies. If necessary, the CMP objectives and the CMP itself will be adjusted.

Source: Durham-Chapel Hill-Carrboro MPO


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