Congestion Management Process

A successful Congestion Management Process (CMP) must include various actionable activities that follow a general sequence and are cyclical in nature. The federal guidelines list eight actions that form the major components of a CMP which can be integrated into the regional planning process. The following eight items explain how ARC addresses congestion through a systematic process and provides a framework for responding to congestion in a consistent and coordinated fashion.

1. Develop Regional Objectives for Congestion Management

In keeping with the objectives of the Regional Transportation Plan, the CMP must work towards feasible outcomes by first defining the objectives for congestion management. Rather than trying to eliminate all forms of congestion at once, developing objectives will help accomplish specific outcomes. ARC has integrated the CMP within the objective development process for the regional plan. One ongoing objective is to foster the application of advanced technologies such as synchronized signal timing, which improves roadway reliability and throughput. This objective is being actively pursued in the Regional Transportation System Management and Operations (TSMO) Plan.

Policy Framework of the Atlanta Region’s Plan

2. Define CMP Network

ARC developed a Regional Thoroughfare Network (RTN) with the intent to focus future transportation system management, operations, and maintenance activities on critical corridors to protect or enhance regional multimodal activity. RTN acts as the CMP network as well. Based on the identified need to promote mobility, connectivity, multimodal, and freight travel at a regional scale, the following established regional networks comprise the set of core criteria utilized for the identification of the RTN:

  1. National Highway System
  2. Principal Arterials
  3. Regional Mobility Roadway Segments
  4. Regional Truck Routes
  5. Premium Transit Roadway Alignments
  6. GDOT Regional Traffic Signal Operations Program Corridors

The RTN was developed in part as a network to receive priority consideration for funding given its importance in moving the traveling public in the Atlanta region through various transportation modes. The process for identifying the RTN was completed using the following three steps:

Develop Draft Networks
  • Review plans and policies
  • Review available data
  • Linkage to Unified Growth Policy Map (UGPM) and Travel Design Lines
Quantitative Analysis
  • Based on Travel Demand Model
  • Discounted for interstate trips
  • Several scenarios analyzed
Network Refinement
  • Input from TCC and stakeholders
  • GDOT recommendations
  • Linkage to UGPM and Travel Desire Lines

3. Develop Multimodal Performance Measures

The performance measures in a CMP support the regional objectives and enable measuring congestion on a local as well as regional scale. The funding program signed into law by President Obama in July 2013, Moving Ahead for Progress in the 21st Century (MAP-21), established a performance-based program to encourage states and MPO’s to invest in projects that make progress toward national goals. MAP-21 was followed by Fixing America’s Surface Transportation (FAST) Act in 2015, which further emphasized performance-based planning. MPO’s in particular must work with their state DOT’s and include performance targets as a part of the metropolitan planning process.

As a follow up to the RTN classification process, available data sources were assessed to derive the performance measures and the identification of performance measure targets. The following table illustrates the range of measures to be considered in this process.


4. Collect Data/Monitor System Performance

ARC uses observed system performance data from INRIX to analyze congestion as part of the CMP. ARC also created a Key Network that combines data from disparate data sources, including the RTN, INRIX data, freight, and safety among others. The Key Network is paired with land use, environmental justice, and environmental and community resources to use as a foundation for ongoing monitoring of system performance. The following graphic is a snapshot of how the data ARC collects feeds into the Key Network and ultimately project performance measures.

5. Analyze Congestion Problems and Needs

This step of the CMP is crucial in understanding the types and levels of congestion that are currently present in the CMP Network or forecasted in the future. ARC uses DASH, a visualization tool for Federal and agency specific performance measures, to analyze congestion and implement mitigation strategies.

Types of Congestion

Causes of congestion can be grouped into two different categories: recurring and nonrecurring. Recurring congestion reflects the normal or routine commuting patterns that typically occur during the morning and afternoon rush hours. This type of congestion is often predictable because the travel routes follow a specific pattern in terms of time of day and route selection. On the other hand, nonrecurring conditions are often caused by crashes, construction, and bad weather that do not recur at the same location on a regular basis.  This type of congestion is more difficult to measure and predict, especially at a regional level.

To this end, ARC focuses on analyzing recurring congestion. ARC defines congestion as occurring when observed demand or volume reaches or exceeds what a roadway or transit facility can handle. The following three variables are used to quantify congestion.

  • Intensity — assesses how much delay is experienced by the average commuter.
  • Duration — measures how many hours during the day a facility experiences congestion.
  • Extent — identifies the number of people impacted by congestion.

How ARC Analyzes Congestion

In addition to utilizing INRIX raw data, ARC utilizes the RITIS Probe Data Analytics Suite as a means of determining the extent and severity of recurring congestion. The trend map tool allows us to show changes in congestion for specific time periods and at various granularities. The bottleneck tool ranks congestion locations over long periods of time and highlights the location with the greatest impact.

ARC recognizes that transit plays an important role in our regional transportation system and should be analyzed specifically in the CMP. On-time performance of buses is a good indicator of congestion because bus routes are primarily located on key arterial streets. Currently, ARC utilizes General Transit Feed Specification (GTFS) data to evaluate on-time performance by comparing scheduled times with observed data for premium transit roadway alignments.

6. Identify and Assess Strategies

By understanding the extent and types of congestion in the Atlanta region, ARC and its partner agencies are able to identify context-sensitive strategies for mitigation.

ARC provides technical assistance for congestion mitigation through our Mobility Services Group, which focuses on Transportation Demand Management and has many programming efforts such as Georgia Commute Options, and Biketober. Additionally, ARC also prioritizes operation strategies for appropriate projects through The Policy Framework, ARC’s visioning document. Typically, county Comprehensive Transportation Plans (CTP) identify congestion management strategies, including operation strategies. The recommendations are then translated into projects by the local government and submitted to ARC for evaluation.

Active operational management and a Safe System approach to planning also helps mitigate nonrecurring congestion. For instance, the Regional Transportation Systems Management and Operations (TSMO) Plan, which evaluates the region’s current technological capacity and creates a roadmap for the future. Also, the Safe Streets for Walking & Bicycling plan establishes a regional approach to eliminating fatal and serious injury crashes using a data-driven approach. Safe Streets identifies and eliminates roadway and intersections risks, thus helping to prevent crashes that contribute to nonrecurring congestion. Other initiatives in the region for non recurring congestion mitigation are being implemented, such as GDOT’s Highway Emergency Response Operators (HEROs) program, the traveler information system Georgia Navigator, and the managed lane initiative Major Mobility Investment Program (MMIP).

7. Program and Implement Strategies

A vital role of an MPO is to use performance-driven planning to program projects for federal funding. ARC’s Project Evaluation Framework uses data to analyze, compare, and select proposed projects submitted by local governments for the Transportation Improvement Program (TIP) and the Livable Centers Initiative (LCI) Program. Using the Framework, projects are evaluated by primary project type which allows for an apples-to-apples comparison among projects with consistent performance measures and metrics. All of the data sources mentioned in Step 4 are included in this evaluation process. ARC also uses the Congestion Management and Air Quality (CMAQ) Calculator to determine emissions and congestion benefits eligible projects including operational improvements.

8. Evaluate Strategy Effectiveness

Continued monitoring of the Congestion Management Process informs where strategies can be improved and where the process is working well. This monitoring happens as a part of the Regional Transportation Plan update process. ARC identified performance measures to track trends in the overall effectiveness of investments in the region’s transportation system. Current performance measures can be found in the Regional Transportation Plan and are also in the process of being updated. DASH also houses a subset of these performance measures in a more interactive and dynamic way.

When ARC created the RTN in 2011, a series of case studies were performed along RTN corridors to test the effectiveness of congestion reduction policies and projects. Three of the reports from those case studies are available below.