Congestion Management System

Chapter 4: Congestion Mitigation Strategies

This section deals with outlining a menu of strategies that can be used to mitigate the congested intersections and sections of roadways identified in Chapter 3. As mentioned earlier, the intent of the CMS is to investigate first the congestion mitigation strategies that target a reduction in transportation demand before resorting to new roadway construction or widening projects that serve single-occupant vehicles.

4.1: TEA-21 Required Congestion Mitigation Strategies
Following are categories of congestion mitigation strategies that were identified in the TEA-21 guidelines for CMS development:

(1) Transportation Demand Management Measures
(2) Traffic Operational Improvements
(3) Public Transportation Improvements
(4) ITS Technologies
(5) Additional System Capacity

4.2: Knoxville CMS Toolbox of Congestion Mitigation Strategies
From the TEA-21 guidelines, a broader menu of more specific strategies within each of the above categories has been developed for use in the Knoxville Urban Area. The menu will be listed in the order in which each strategy should be analyzed, although the very first step in the analysis will be to identify whether a project is already under development for any of the sections, and what stage of development it is in. The following table presents the menu, or “Toolbox” of strategies that are available.

 

TABLE 4-1: Congestion Mitigation Strategy Toolbox

Strategy Class	Strategy Group	Representative Strategies
Strategy1– Transportation Demand Management	A. Growth Management/Land Use Controls	Promote Infill, Compact and Mixed-use Development Enforce Growth Boundaries - Limit Rural Area Growth Development Standards - Require sidewalks with new subdivisions
	B. Congestion Pricing Controls	Road User Fees/Peak Hour Tolls Parking Fees
	C. Ridesharing Programs	Carpool/Vanpool and Transit Incentives HOV Priority Systems Employer Trip Reduction Programs Guaranteed Ride Home Program
	D. Alternative Work Arrangements	Telecommuting Flexible work hours
	E. Non-Traditional Mode Incentives	Improved/Expanded bicycle network Bicycle storage systems Improved/Expanded pedestrian network
Strategy 2 – Traffic Operational Improvements	A. Traffic Signal Improvements	Signal re-timing Addition of vehicle presence detection Additional signal department staffing
	B. Roadway Geometric Improvements	Bottle-neck alleviation Turn lane additions at intersections Re-striping/lane assignment modifications
	C. Turn Restrictions	Time-of-day restrictions on turning movements
	D. Ramp Metering	Meter freeway entrances to manage traffic flow
	E. Access Management	Driveway Management Median Management
	F. Construction Management	Encourage construction activities in off-peak times Coordinate traffic management plans
Strategy 3 –Public Transportation Improvements	A. Transit Capital Improvements	Incident detection/surveillance Fleet expansion Transit Support Facilities
	B. Transit Operational Improvements	Route enhancements Increased marketing of transit services Fare incentives Signal priority
Strategy 4 – Intelligent Transportation Systems	A. Incident Management	Incident detection/surveillance Incident response/service patrols
	B. Advanced Traffic Management Systems	Traffic Management Centers Traffic signal coordination/traffic adaptive signal timing
	C. Advanced Traveler Information Systems	Dynamic Message Signs Highway Advisory Radio
	D. Advanced Public Transportation Systems	Automated vehicle location “Smart” bus stops
	E. National ITS Architecture	Additional user services from ITS Architecture
Strategy 5 – Additional System Capacity	A. Additional Freeway Lanes	Adding capacity with construction of general purpose travel lanes
	B. Additional Arterial Lanes	Adding capacity with construction of general purpose travel lanes
	C. New Roadway Construction	Construction on new alignment, “bypass” type routes

4.3: Description of Mitigation Strategies
More information and a detailed description of each of the strategies is given below:

Strategy 1 – Transportation Demand Management (TDM)
TDM measures are designed to reduce the amount of traffic on the roadway through reduction in travel demand. The main intent of many of these strategies is to reduce the amount of travel demand that is occurring during the peak hours since these are the times of most roadway congestion.

In order to be especially effective, TDM measures usually involve the need for either an incentive or disincentive as part of their implementation. For example, more people will agree to carpool or vanpool if there is a facility that gives priority to High Occupancy Vehicles (HOV), which will improve their travel time. On the other hand, fewer people will drive alone if parking costs are increased substantially.

• 1.A. Growth Management/Land Use Controls:
  Land use influences a great many factors in terms of the amount of travel that occurs in an area. Especially affected is the number and length of trips that are made, or the overall number of Vehicle Miles Traveled (VMT). By allowing continued low-density growth in cul-de-sac suburban neighborhoods, traffic congestion will continue to increase as people are forced to drive to their destination, usually with longer travel distances, especially work commute trips which dominate the peak hour travel purpose.
  • 1.A.1 – Promote Infill, Compact, and Mixed- Development: These development patterns tend to reduce the need for automobile travel by providing necessary services within close proximity to one another. This encourages the use of alternative modes such as walking or bicycling, and can provide the necessary densities to support transit services.
  • 1.A.2 – Enforce Growth Boundaries: The State of Tennessee required all counties to work cooperatively in setting urban growth plans. The growth plan designates all land in the county into one of three categories: urbanized area, planned growth area, and rural area. The rural area designation carries with it a require- ment that only low-density growth can occur there. These boundaries should be enforced so that the continued outward growth of cities is contained, thereby reducing the trip lengths that would be required.
  • 1.A.3 – Development Standards: This is a broad definition of requiring new developments to provide necessary infrastructure to accommodate alternative transportation modes. These standards can include requiring smaller front setbacks for retail shopping centers, which facilitates transit service – to requiring sidewalks to be built along with new residential subdivisions. Standards reducing the number of cul-de-sacs help promote alternative modes by increasing connectivity of the transportation system.
    
    
• 1.B. Congestion Pricing Controls:
  This strategy involves reducing demand on roadways by charging a fee to motorists, particularly during peak hours. These fees can be direct road user fees such as tolls, or be imposed through increased parking fees. It can be very difficult to institute new road user fees on roads that are currently toll-free, and requires a high level of public and political support before being instituted. In addition, parking fees may tend to discourage downtown redevelopment activities.
  • 1.B.1 – Road User Fees: Road user fees can be instituted to redistribute or eliminate trips. They can consist of toll facilities, increased fuel taxes, or increased registration fees to discourage the use of automobiles.
  • 1.B.2 – Parking Fees: This strategy involves the increase in direct out-of-pocket costs to park private automobiles, which can discourage driving. They can be instituted by public and private sector parking providers.
    
    
• 1.C. Ridesharing Programs: A great deal of the increase in congestion over the last decade can be attributed to the trend in decreasing vehicle occupancy rates due to fewer commuters carpooling. Ridesharing programs are intended to reverse this trend by providing incentives for people to carpool and vanpool.
  • 1.C.1 – Carpool/Vanpool and Transit Incentives: Subsidies can be provided to promote the use of carpools, vanpools, and transit by giving an economic incentive to their use. These incentives can include programs by individual employers such as providing free parking to these users, providing free transit passes, or regional programs which subsidize the purchase of vans.
  • 1.C.2 – HOV Priority Systems: In order to promote the use of high occupancy vehicles, it is often necessary to show a time savings benefit, which can be accomplished through the construction of HOV priority systems. These systems include roadway facilities or lanes that are reserved exclusively for HOVs. Restrictions on their use can include entire days, or just peak hours when congestion is worst.
  • 1.C.3 – Employer Trip Reduction Programs: These are requirements placed on employers to reduce single occupant vehicle commuting.
  • 1.C.4 – Guaranteed Ride Home Program: This program promotes the use of alternate modes by providing a free ride (usually a taxi fare) to a person who needs to get somewhere when there is an emergency or other circumstances, when they do not have access to their personal vehicle due to carpooling or the use of an alternative mode.
• 1.D. Alternative Work Arrangements: The goal of this strategy group is to spread out the peak hour travel, which mainly consists of work trip purposes.
  • 1.D.1 – Telecommuting: By allowing and promoting telecommuting, work trips can be eliminated altogether.
  • 1.D.2 – Flexible Work Hours: There are a variety of programs that can be offered by large em- ployers to allow employees to shift their work times around a flexible schedule instead of everyone arriving within the same timeframe.
• 1.E. Non-Traditional Mode Incentives: These incentives are geared towards making the use of non-traditional transportation modes such as bicycling and walking more available and friendly.
  • 1.E.1 – Improved/Expanded Bicycle Network: Includes on-road facilities and shared use paths.
  • 1.E.2 – Bicycle Storage Systems: This involves providing safe and secure locations for bicyclists to park their bicycles in public places. Convenience to destinations should also be considered in their location.
  • 1.E.3 – Improved/Expanded Pedestrian Network: Includes sidewalks, greenways and pedestrian over/underpasses.

Strategy 2 – Traffic Operational Improvements
The strategy of providing traffic operational improvements aims to make more efficient use and management of the transportation infrastructure that is already in place, and to alleviate bottlenecks in the system. Adequate staffing levels need to be available so that the necessary maintenance of traffic signal equipment, such as re-timing and repairing faulty vehicle loop detectors is continued on a timely basis.

• 2.A. Traffic Signal Improvements: Traffic signals are very important in the daily operations of many transportation facilities, and can greatly influence the amount of delays and congestion for motorists. It is critical that proper signal timing plans are instituted to ensure the most efficient allocation of green time.
  • 2.A.1 – Signal Re-Timing: The re-timing of signals to respond to yearly, or even seasonal changes in traffic flow patterns is crucial to maintain efficient traffic operations. This can be a very time and labor intensive task, however, as it requires updated turning movement counts at the signalized intersections.
  • 2.A.2 – Addition of vehicle presence detection: Efficiency of a traffic signal can be greatly improved if vehicle detectors are installed. These vehicle detectors have recently evolved into newer technologies using video cameras to detect vehicles instead of the traditional method of installing a magnetic loop in the pavement. The video detection allows a completely non-intrusive method of detection, which means that lanes of traffic do not have to be blocked for repairs, and they do not get damaged every time a re-paving project occurs.
  • 2.A.3 – Additional signal department staffing: A study was performed in 2001, which compared staffing levels of signal departments around the southeast with Knoxville’s3. The study found that Knoxville had fewer resources and staffing per signal than other comparable cities. As the number of traffic signals has increased over the past several years, the level of staff responsible for their maintenance has remained constant. It is important that timely maintenance and update of signal timing occurs, but is not possible without adequate personnel.
    
    
• 2.B. Roadway Geometric Improvements: This strategy group involves physical improvements that can be made to improve efficiency of the roadway.
  • 2.B.1 – Bottleneck alleviation: The amount of congestion on a roadway can often be caused by one or two bottleneck points that restrict capacity and influence long stretches of roadway. Bottlenecks can occur when a facility drops a lane suddenly, only to widen back out later, or when deficient length of acceleration/deceleration lanes cause traffic to slow down.
  • 2.B.2 – Turn lane additions at intersections: Significant delays can be caused by a single vehicle that is attempting to make a left turn at an intersection that blocks all of the through vehicles behind it. Therefore intersections, particularly signalized intersections, should have an adequate number and length of turn lanes to operate efficiently.
  • 2.B.3 – Re-striping/lane assignment modifications: Often, an intersection can operate more efficiently by studying whether an exclusive lane can be re-striped to include a shared turn lane, or vice-versa. This strategy deals with exploring these possibilities at congested locations to determine whether these low-cost, easily implemented measures can be made.
    
    
• 2.C. Turn Restrictions: - Time-of-day restrictions on turning movements: It may be possible to alleviate congestion problems where it is not feasible to construct a turn lane by simply placing signs that prohibit the particular turn movement during certain periods of high traffic. This strategy often requires a period of getting used to by the traveling public, and may require enforcement to be effective.
  
  
• 2.D. Ramp Metering: - Meter freeway entrances to manage traffic flow: This strategy has been shown to be effective in maintaining an efficient traffic flow on the most important functional class of roadway – the freeway. It must be intensively studied before implementation though, to ensure that adequate storage exists on the on-ramps to ensure that back-ups do not hinder flow on the surface street network.
  
  
• 2.E. Access Management: Roadways generally serve two basic functions – access and mobility, unfortunately these are competing functions. In a proper functional classification scheme, arterials have mobility as their primary purpose. Oftentimes, though, several commercial establishments develop along these roadways, each desiring their own driveway. The strategy group of access management deals with ways to reduce the friction that these driveways cause on traffic flow.
  • 2.E.1 – Driveway Management: This strategy involves controlling the number of driveways along a roadway. It can include restrictions on the number of driveways with new development or consolidation of existing driveways, which can be accomplished in the reconstruction of roadways.
  • 2.E.2 – Median Management: The installation of a median can automatically control the amount of access on the roadway. Median management deals with regulations that are placed on the spacing required between median openings. It also is something should be considered in the reconstruction of a two-lane roadway, rather than the construction of a continuous two way left turn lane, which permits unlimited access.
    
    
• 2.F. Construction Management: Most urbanized areas have seen a drastic increase in the amount of roadway construction. Since the amount of capacity often is seriously impacted while a road is being reconstructed due to narrower or fewer lanes, it is important that these activities are coordinated to have the least possible impact.
  • 2.F.1 – Encourage construction during off-peak times: This strategy involves doing short-term construction activities that will require major disruption to only the off-peak hours. This can include non-traditional activities such as utility work that is within a roadway.
  • 2.F.2 – Coordinate traffic management plans: The coordination of traffic management during a large construction project often requires inter-jurisdictional cooperation. It is often necessary to coordinate weekly meetings among officials to ensure detours are being properly set-up and necessary modifications to signal timings are made.

     

Strategy 3 – Public Transportation Improvements
The use of public transportation can become much more attractive to potential riders through capital and operational improvements to the system, thereby reducing the reliance on private automobiles for transportation.

• 3.A. Transit Capital Improvements: Capital improvements to the existing public transportation system will result in increased opportunities to serve the needs of the existing and potential ridership.
  • 3.A.1 – New exclusive right-of-way service (bus or rail): The most efficient transit service occurs when the transit vehicle operates on a separate right-of-way from the regular traffic stream. These improvements can be very costly, although newer forms of this service such as bus rapid transit (BRT) have emerged that are more cost effective than traditional rail services. However, service on exclusive right-of-way often requires a certain level of population density to be cost effective.
  • 3.A.2 – Fleet Expansion: Fleet expansion can consist of the addition of new types of transit vehicles that respond better to particular service needs.
  • 3.A.3 – Transit Support Facilities: This strategy group involves the construction of new facilities that serve as access points to transit services. It is important in attracting new riders to have safe, convenient locations to access the transit system. Examples would be construction of park-and-ride lots, bus shelters, transit transfer stations and intermodal facilities.
    
    
• 3.B. Transit Operational Improvements: This strategy group involves enhancing the existing service by improving its efficiency and attractiveness to current non-users of the transit system.
  • 3.B.1 – Route Enhancements: The transit authority must continually reassess its route structure to determine where service is needed and the frequency of it. Various types of services ranging from small neighborhood circulators to long-distance express routes need to be incorporated into the overall route structure.
  • 3.B.2 – Increased marketing of transit services: Often people are not aware that transit service is available, or which routes go where. Therefore increased marketing of the transit services that are available can increase mode shift from automobile to transit.
  • 3.B.3 – Fare Incentives: People can be tempted to take transit when reduced fares are offered. This strategy is often packaged with some of the TDM strategies mentioned earlier such as Employer Trip Reduction programs.
  • 3.B.4 – Signal Priority: A bus that must travel with the regular traffic stream is often seen as not being more attractive than using one’s own vehicle because they are both subject to the same delays. There are systems however that allow transit vehicles the ability to preempt traffic signals so that they can achieve favorable travel times.

Strategy 4 – Intelligent Transportation Systems
Intelligent Transportation Systems (ITS) refer to the use of advanced technologies to enhance the operations and efficiency of a transportation facility. This strategy is basically a technological extension of several of the strategies identified previously, especially the ones dealing with traffic operational improvements.

• 4.A. Incident Management:
  • 4.A.1 – Incident Detection/Surveillance: Typically incident detection is used on freeway facilities to determine the exact cause of disruption in flow to send the appropriate response to clear it. Incident detection can be performed using speed-monitoring devices that detect an abnormal slow down in traffic, or by using cameras placed along the freeway to actually view the traffic.
  • 4.A.2 – Incident Response/Service Patrols: Once an incident is identified, it is important to have the necessary equipment to respond that can set-up temporary traffic control, such as a freeway service patrol.
    
    
• 4.B. Advanced Traffic Management Systems:
  • 4.B.1 – Traffic Management Centers: A Traffic Management Center is a central location where traffic is monitored and decisions are made in terms of incident response and appropriate information to display on dynamic message signs.
  • 4.B.2 – Traffic signal coordination/traffic adaptive signal timing: Developments in the technology for traffic signals allow the coordination of several signals by allowing them to “communicate” with one another. It is also possible to program algorithms that respond dynamically to changing traffic conditions automatically by re-adjusting the signal timing instantaneously, such as when a large volume of traffic suddenly diverts from the freeway onto an arterial.
    
    
• 4.C. Advanced Traveler Information Systems:
  • 4.C.1 – Dynamic Message Signs: The use of dynamic message signs (DMS) on freeways at key decision points allows for a motorist to be informed of real-time traffic conditions and incidents ahead so that they can avoid congestion by deviating their route.
  • 4.C.2 – Highway Advisory Radio: Similar to a DMS, the highway advisory radio (HAR) allows motorists to tune into a specific radio station to get real-time traffic conditions to aid in planning their route.
    
    
• 4.D. Advanced Public Transportation Systems:
  • 4.D.1 – Automated Vehicle Location: There are technologies available to enable the transit provider to know the exact location of each transit vehicle in the system, known as automated vehicle location (AVL). This information can enhance the transit service being provided.
  • 4.D.2 – “Smart” Bus Stops: With the addition of the AVL technology noted above, bus stops can be outfitted with terminals that provide real-time information on when the next vehicle will be arriving. This technology makes the use of transit much more attractive to utilize.
    
    
• 4.E. National ITS Architecture:
  • 4.E.1 – Additional User Services: The National ITS Architecture has identified over 30 different user services where ITS technologies can be applied to enhance the transportation system. There will be opportunity to incorporate more of these user services as they become feasible in the future.

Strategy 5 – Additional System Capacity
This strategy group involves the construction of new general-purpose lanes to existing facilities, or constructing facilities on new alignment to alleviate congested corridors. Although capacity expansion can be appropriate for a number of situations, it is necessary to first analyze the previously noted strategies before undertaking roadway construction. The cost of roadway construction continues to increase because of higher right-of-way costs, and there is typically strong public opposition due to the impacts on personal property and the environment.

At the very least, capacity expansion projects need to incorporate the above strategies wherever possible so that the public investment is protected. An example of “packaging” a strategy with capacity expansion is strategy 2.E. (Access Management) where a median should be constructed instead of a two way left turn lane and driveways should be consolidated wherever possible. Another example would be the construction of bicycle lanes and sidewalks with all roadway reconstruction projects. In fact, the US Department of Transportation has released a policy statement on integrating bicycling and walking into transportation infrastructure. Essentially, the statement says that well-designed bikeways must be included in roadway projects that receive federal funding.

• 5.A. Additional Freeway Lanes:
  • 5.A.1 – Additional capacity with the construction of general purpose lanes
    
    
• 5.B. Additional Arterial Lanes:
  • 5.B.1 – Additional capacity with the construction of general purpose lanes
    
    
• 5.C. New Roadway Construction:
  • 5.C.1 – Construction on new alignment, “bypass” type routes

4.4: Selection of Mitigation Strategies
The TPO staff organized separate Technical Committee taskforces for Knox and Blount Counties in order to determine which congestion mitigation strategies were appropriate for each specific roadway or intersection that was found to be “congested”. There may be more than one appropriate strategy for a particular congested location, in fact many times there can be synergistic effects that multiply the benefits of two or more strategies that are implemented simultaneously.

The taskforces based their recommendations on the information in this report plus answering basic questions such as “what is causing the congestion at this location?” and “which remedies make the most sense?” Appendix C includes the summary of the characteristics of each congested corridor, which was used for discussion at these meetings. A summary of the strategies that were selected for each congested roadway is included in Chapter 7 at the end of this report.