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Congestion Management

Photo courtesy of Garrett via Flickr/Creative Commons license.

The congestion management process (CMP) is an analysis tool to support development of the Regional Transportation Plan (RTP) and the Transportation Improvement Program (TIP) for the Wasatch Front Regional Council (WFRC). The CMP identifies congestion reduction needs and provides information and suggestions to decision-makers, in an effort to meet those needs. Demand management and system management strategies are evaluated with the intent to reduce the congestion without increasing highway capacity, or to maximize efficient traffic operations when additional capacity is warranted. The results of the CMP contribute to an efficient and effective transportation system, increased mobility and accessibility, and maximized utility from limited resources.

The CMP defines a number of performance measures and strategies to relieve congestion. Analyzing modeled and actual data facilitates the identification of congested locations and evaluation of congestion relief strategies. The CMP evaluates various system management and demand management strategies and suggests appropriate strategies by functional class of highway, as well as Urban Surface Transportation Program (STP) projects identified in the TIP.

Another role of the CMP is to determine if additional capacity is warranted by demonstrating whether anticipated congestion can be relieved by transportation demand management (TDM) and transportation system management (TSM) strategies alone. In the event additional capacity is needed, the CMP recommends TSM and TDM strategies to be incorporated into the new capacity projects. Corridors where TDM and TSM strategies can postpone or eliminate the need to add capacity are also identified.

For additional information regarding congestion management, please contact Kip Billings.

Based on the Highway Capacity Manual’s definition of level of service (LOS), the CMP defines congestion as LOS “E” or worse, which is based on volume/capacity ratios for freeways and operating speeds for arterials. It should be noted that this criterion is supplemented with engineering judgment since traffic model results are a better reflection of relative changes, rather than absolute changes in traffic conditions. With this in mind, it should also be noted that modeling results should be used with discretion as a decision tool and not as a definitive design requirement.

Data collection is necessary in order to support a more in-depth understanding of congestion. Data collection activities focus on four areas, including system monitoring, congestion identification, causes of congestion, and project level “before and after” data. Historically, data collection has been a challenge due to limited resources and the high cost of manual data collection. New probe data technology is a very promising, low-cost method to collect larger and more accurate sets of data. The CMP explores opportunities to utilize probe data, such as Bluetooth technology as it becomes available, and coordinates with the Utah Department of Transportation (UDOT) and Utah Transit Authority (UTA) in this effort.

Using the LOS “E” criterion described in the “Performance Measure and Data Collection” section, WFRC identified congested locations in the region. The CMP identified the following two types of congested roadways.

  1. Congestion that can be alleviated with TSM and TDM strategies and
  2. Congestion that requires increased roadway capacity, in addition to TSM and TDM improvements.

The map showing congested locations and management recommendations may be found in the “Helpful Links and Downloads” section.

The arsenal of strategies to lessen congestion is expanding. With urban Utah’s rapid growth, the addition of new general-purpose traffic capacity is necessary to manage future congestion. Yet, experience from around the country points to the fact that new travel demand will inevitably outpace the ability to provide new travel capacity. The ability to better manage the system, including maximizing the effectiveness of signal systems and maintaining existing traffic capacity, are strategies which should be given considerable attention. Better ways to manage demand for additional travel must also be considered.

More efficient means of travel should be identified and supported in order to allow existing revenue sources to meet the public’s demand for efficient mobility. The following list provides many of the traditional, as well as nontraditional, congestion mitigation controls available to the Wasatch Front region.

Demand Management Strategies

  • Rideshare promotion
  • Car sharing
  • Staggered and flexible work hours
  • Telecommuting
  • Growth planning
  • Transit improvements
  • High occupancy vehicle (HOV) lanes
  • Park-and-ride lots
  • Active transportation
  • Employer commute programs
  • Trip reduction programs
  • Congestion pricing
  • Parking management
  • Auto-related taxes/fees

System Management Strategies

  • Signal system improvements/coordination
  • Capacity additions
  • Access management
  • Intelligent transportation systems
  • Incident management
  • Reversible lanes
  • Ramp metering
  • Intersection/interchange geometrics
  • Managed motorways
  • Connected vehicles

Congestion management strategies, beyond direct additions of traffic capacity, have a positive yet limited potential to address the challenge of growing traffic congestion in the Wasatch Front region. Nontraditional congestion management solutions must be considered from two perspectives if they are going to successfully mitigate urban congestion.

First, a program of regional congestion mitigation strategies is developed as part of the transportation planning process (see the list of strategies in the “Congestion Mitigation Strategies” section. Admittedly, some regional solutions offer relatively small advantages to specific congested locations. However, on an aggregate basis, combinations of these regional strategies can have measurable effects.

Second, site specific congestion mitigation strategies are encouraged in two ways. Sponsors of new capacity projects must continue to explore operational enhancements to new traffic capacity, which could improve and maintain the LOS of the new capacity project, as well as reduce the demand for single occupant vehicles. A checklist of operational enhancements and demand management strategies appropriate for each highway functional class has been compiled and can be found in the “Helpful Links and Downloads” section. WFRC staff make follow-up visits to individual project sponsors to review appropriate congestion mitigation strategies. City and county planners also target projects in an effort to implement congestion mitigation strategies using funds from the Congestion Mitigation and Air Quality (CMAQ) program.

Although engineers, planners, and economists often have a preferred “solution” to congestion and mobility challenges, there really is no single solution. To be effective, one needs to examine how congestion mitigation actions complement one another and, over the long-term, how these actions will influence future travel patterns.

In order to evaluate the need for additional capacity, WFRC staff models roadway LOS under two conditions. The CMP includes modeling a “no-build” scenario (existing highway network, future travel demand, and future transit service) and a “CMP” scenario which adds TSM and TDM strategies to the “no-build” scenario. Appropriate TSM and TDM strategies are defined in mathematical terms in the travel demand model as increased speed or reduced volume. Each link in the model can then be analyzed to determine if TSM and TDM strategies alone can meet projected demand or if additional capacity is warranted.

WFRC uses Bluetooth data from the iPEMS database to compare before and after conditions at select CMP project locations. A selection of recently completed CMP projects is identified for which before and after traffic data exists. The iPEMS data for the roadway segments corresponding to the CMP project can then be compared for the two dates: pre-construction and post-construction. The iPEMS data reports for speed, travel time, and delay were used to measure traffic performance. Assessing the benefits of specific CMP projects is complicated by other factors affecting traffic performance that can change during the construction phase such as growing traffic demand, altered travel patterns, impacts of adjacent construction projects, and changes in land use. However, general levels of effectiveness can be determined and facilitate assessment of the projects.

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