Congestion Management System
Chapter 1: Introduction
1.1: Overview and Background Information
The requirement for a Congestion Management System (CMS) originated from the federal Intermodal Surface Transportation Efficiency Act (ISTEA) legislation, which was passed in 1991. The CMS as well as five other transportation management systems(1) were instituted as a means to achieve the major objective of the ISTEA legislation which was to improve the efficiency and safety of, and protect the investment in, the nation’s transportation infrastructure. These management systems are now optional for State Departments of Transportation under the Transportation Equity Act for the 21st Century (TEA-21), which is the update to ISTEA. The CMS, however, is still required of Metropolitan Planning Organizations that qualify as a Transportation Management Area (TMA), which is an urbanized area with greater than 200,000 population. The Knoxville Urban Area, with a 2000 Census population of 419,830, qualifies as a TMA.
The CMS is viewed as an important component in the transportation planning process because of the need to look for alternative means of increasing mobility on the existing transportation system without relying on just new roadway construction or widening projects. Furthermore, the CMS will provide information to assist in the transportation planning process, and be incorporated into the Long Range Transportation Plan and Transportation Improvement Program (TIP) for implementation.
1.2 : TEA-21 Requirements for Congestion Management Systems
The overall intent of a CMS according to the TEA-21 legislation is to provide an effective and systematic process for managing congestion by incorporating methodologies for continuous monitoring of the transportation system, and evaluating the most appropriate means for alleviating the congestion, preferably through reduction in transportation demand rather than expanded supply. It is also important that the CMS is specifically tailored to meet the conditions of the particular area where it is implemented. Therefore, the specific requirements from Code of Federal Regulations Part 500.109 state that the CMS shall address the following aspects at the minimum:
(1) System Monitoring – Methods to monitor and evaluate the performance of the multimodal transportation system, identify the causes of congestion, identify and evaluate alternative actions, and evaluate the efficiency and effectiveness of implemented actions.
(2) Performance Measures – Definition of parameters used to measure the extent of congestion based on locally determined thresholds for system performance.
(3) Congestion Identification – Establishment of a data collection program that will provide for adequate system monitoring and that will identify the causes of congestion.
(4) Mitigation Strategies – Identification and evaluation of the strategies that can be used to alleviate congestion – they should be both traditional and, to a greater extent, non-traditional congestion mitigation tools.
(5) Implementation Strategy – Identification of an implementation schedule, and possible funding sources.
(6) Monitoring of CMS Effectiveness – Implementation of a process for periodic assessment of the efficiency and effectiveness of implemented strategies.
Another major requirement of the CMS is that in TMA’s designated as non-attainment for carbon monoxide and/or ozone, the CMS shall provide an appropriate analysis of all reasonable travel demand reduction and operational management strategies for the corridor before adding significant capacity for Single Occupant Vehicles such as constructing general purpose lanes or a new highway. The Knoxville region is expected to be designated as non-attainment of the newly adopted 8-hour ozone standard set by the Environmental Protection Agency by 2004.
1.3: CMS Interaction with Overall Transportation Planning Process
The CMS is not intended to replace the existing transportation planning process, but is designed to supplement and feed into it. Congestion will remain just one of a number of factors that are considered in project selection and programming. Figure 1 depicts the major steps of the CMS and how it will fit in with the overall Knoxville Regional Transportation Planning Organization (TPO) transportation planning process:
Figure 1: Congestion Management System Interaction
with the Transportation Planning Process
The preceding figure is a general overview. A comprehensive flowchart detailing the exact processes required for the CMS will be presented at the conclusion of this document to facilitate future operations. An attempt will also be made to automate the CMS process wherever possible using computer software techniques to store and analyze necessary data inputs.
1.4: Defining the Transportation Modes
The first step in defining the CMS system is to determine the transportation modes that will be considered in the analysis. According to federal guidelines, the CMS should be multimodal in nature and therefore the following transportation modes were considered for analysis: automobile, bus, air, bicycle, pedestrian, and freight transport.
Due to current time and data constraints, the congestion identification analysis in this report is limited to that of roadway congestion. Although the level of roadway congestion significantly impacts both personal vehicles and transit vehicles, other factors for transit and alternative modes to the automobile should be incorporated into future updates of the CMS plan. The chapter on Future Considerations included in this document will identify additional suggestions for providing congestion monitoring of alternative modes and freight transport in the future.
1.5: Defining the Transportation Network
The transportation network that will be monitored with the CMS was previously defined by the Tennessee Department of Transportation as the state classified and interstate systems within the urbanized boundary of the TPO. The Knoxville TPO expanded this definition to include all roadways that carried greater than 15,000 average daily traffic (ADT) in the Central Business District (CBD) or greater than 10,000 elsewhere in the TPO study area. The 10,000 ADT threshold was chosen because most two-lane roads can handle that amount of traffic before major widening is necessary. The 15,000 ADT threshold was set because most people expect a greater amount of traffic and delays in a highly built-up urban core area. Map 1 depicts the roadways that are included in the CMS analysis.
Footnotes:
1 The other five management systems were: Pavement Management System, Bridge Management System, Safety Management System, Intermodal Transportation Management System and Public Transportation Management System.
