Office of Operations
21st Century Operations Using 21st Century Technologies

An Agency Guide on How to Establish Localized Congestion Mitigation Programs

2.0 How to Structure a Localized Bottleneck Reduction Improvement Program

2.1 Roles and Responsibilities

There really are no set guidelines for roles and responsibilities of an LBR program. State DOTs, MPOs, or local transportation agencies could all lead an effective LBR effort. State DOTs and MPOs are traditionally the organizations who lead LBR efforts simply because they usually have larger missions, which include bottleneck issues; as well as access to a variety of funding mechanisms. Many successful LBR programs actually depend on a high level of coordination between state DOTs and MPO. Many times, the state may identify bottlenecks and work closely with MPOs to integrate these projects into their TIP and other targeted funding sources such as CMAQ and safety. However the split or leadership role, any transportation agency can lead an effective program.

2.2 Options for Structuring the LBR Program

Those agencies that have been effective at dealing with bottlenecks have developed either special or ongoing programs specifically targeted at dealing with current bottleneck projects. The options for structuring an LBR program vary widely, as described in this section.

Barriers to Establishing the LBR Program

States have cited a number of barriers to establishing bottleneck-specific or similar programs that target chokepoint congestion:

  • A predisposition for large scale, long-term congestion mitigation projects. Traditional transportation planning and programming efforts are often predisposed toward major capital improvement projects to relieve congestion such as corridor-widening or massive reconstruction of an interchange. There is also no shortage of demand management strategies designed to fight the congestion battle, such as HOVs, tolling and pricing, transit alternatives, and ridesharing programs. But the onerous processes involved in many of these initiatives can squeeze out smaller programs.
  • Lack of program identity. Unless there is a formal program identity, bottleneck remediation is usually relegated to a few projects completed as part of an annualized safety program, or as a subordinate part of larger, other purposed projects.
  • Lack of a champion. Many successful state or metropolitan planning organization programs are the result of one or more persons taking charge to either mandate or adopt a program. High-level administrators often set the policy direction and strategic initiatives for their agencies, while mid-level managers’ production reflects their priorities and skills in executing those initiatives.
  • Lack of resources. Many state agencies are finding themselves overworked and understaffed. Although the return on investment for LBR projects are high, agencies often do not have the in-house resources necessary to conduct detailed analyses required to evaluate and prioritize the large number of potentially competing projects. With limited resources, agencies are relegated to hiring consultants and/or universities to conduct detailed project analysis.
  • Lack of funding. With many state agencies experiencing major budget shortfalls, lack of funding continues to be an often cited barrier to implementing new programs.
  • Responsibility has not been assigned. Not part of ongoing planning and programming processes. Localized bottleneck mitigation projects are not often included in the ongoing planning and programming processes for most agencies. Others struggle with how best to identify problem locations, assess existing conditions, and quantify the impacts of proposed remedies, as there is no structured process in place. For example, in developing their structured LBR program, Michigan DOT cited challenges regarding how best to justify and evaluate project impacts while creating a level playing field for application of LBR funding across each of their seven regions.
  • A culture of historical practices. Many agencies face institutional challenges in changing their current business practices. For example, one agency dutifully executed an annualized “safety” program and looked only at crash rates in determining their annual top 10 list of projects. After instituting a congestion mapping process, they identified several significant stand-alone chokepoints that did not correlate with their high-crash mapping. Thereafter, high congestion hot spots competed with high accident hot spots on their unified top 10 list of projects.

The options for structuring an LBR program vary widely. One approach is to undertake a one-time special program or periodic special initiatives that focus on bottlenecks. Other approaches incorporate annualized reviews or ongoing programs – similar to annualized safety-spot lists – that organized candidate locations and identify them for relatively short-term (e.g., two years or less) attention.

Periodic Special Program or Initiative

For example, in 2007, the Minnesota DOT was asked by the Legislature to develop a rapid turnaround plan to identify low-cost, quickly implementable projects that were not already identified by the traditional planning and programming processes. In a matter of months, this unique approach led by the Traffic Management Center engineers basically “brainstormed” low-cost, candidate projects that were nagging problems, but for whatever reasons, had never landed on traditional Capital Improvement Programs. In 2008, the Central Arkansas MPOs undertook “Operation Bottleneck,” a campaign to openly solicit public input of candidate locations, but one that has a finite life span.

Due to resource limitations, some agencies are using research funds to sponsor special projects involving in-depth analysis of the causes and temporal variations at key bottleneck locations. For example, in the Phoenix metropolitan region, Arizona DOT commissioned a special research study to identify freeway bottlenecks and provide a detailed assessment and recommendations of countermeasures. Wisconsin DOT partnered with a research agency to identify bottleneck reduction strategies and to develop a Paramics model to perform in-depth simulation of the proposed strategies. They plan to expand the project to include other bottleneck locations statewide.

Incorporating Bottlenecks into Other Programs

State DOT Level

At the state DOT level, low-cost bottlenecks can be addressed programmatically even without a special program or initiative. One approach is to conduct a review of existing plans and look for opportunities to include LBR improvements in them. For example, Caltrans, as part of their Corridor Management Process, includes the identification of bottlenecks and potential short-term fixes as part of an overall and long-term strategy for making corridor improvements. This often takes the form of an “LBR audit,” which is a review of traditional large-scale corridor studies to identify opportunities for using LBR improvements as part of the package of improvements. The concept here is similar to that of Road Safety Audits.

Another approach is to integrate bottleneck strategies as part of ongoing planning and processes, thereby incorporating them into an agency’s congestion mitigation toolbox. For example, the Ohio DOT added a congestion-based index ranking to their annual identification of spot safety problems for the Federal Hazard Elimination Program (HEP). As a result, congestion hot spots now have a “voice” regardless of crash indices, and congestion-related projects compete for attention in the project selection and scheduling process.

Washington State DOT recognizes bottlenecks and chokepoints as an integral part of their project planning and development process. The recent Moving Washington initiative incorporates LBR concepts into a coordinated program to address congestion. In the Moving Washington program, WSDOT applies three balanced strategies to fight congestion – operate efficiently, manage demand, and add capacity strategically. By strategically adding capacity, WSDOT targets bottlenecks and chokepoints in the transportation system, and does so cost-efficiently. Recent funding shortfalls have made low-cost, strategic investments a high priority with WSDOT and LBR projects fill this role nicely. Performance results show that Moving Washington strategies and projects are making a difference around the State to relieve congestion.

At the planning stage in their Highway System Plan, WSDOT considers bottlenecks together with traditional corridor improvements under the “Congestion Relief” category. Congestion relief projects are ranked using the benefit/cost ratio, contribution to performance goals, and other qualitative factors, and compete on these bases with projects in other categories in the Highway System Plan: Preservation, Safety, Environmental Retrofit, Economic Vitality, and Stewardship.

MPOs Level

At the metropolitan planning organization level, the short-term nature of LBR projects meshes well with the Congestion Management Process (CMP) and “planning for operations,” which are new initiative areas for planners. As planners’ perspectives broaden to include these short-term views of the system (in addition to the traditional long-range view), an LBR program makes perfect sense. In fact, one idea may be to include consideration of an LBR program within one the CMP and/or “planning for operations” guidance being developed by FHWA. The idea is not to make an LBR program subordinate to these initiatives but rather to integrate it into the initiatives, noting that LBR is an effective way to address current congestion problems.

From a planner’s viewpoint, LBR improvements would be another aspect of the CMP process. Because an LBR program should be data- and performance-driven, it is a logical complement to a CMP; the same data should be used for both purposes. In fact, the steps required to implement an LBR program directly mimic the eight-step CMP process: problems are identified, countermeasures are developed to address the problems, funding is identified, and projects are implemented, and evaluation occurs. Figure 2.1 shows the eight-step CMP process, which bears remarkable similarity to the steps that need to occur within an LBR program. An LBR program is a natural extension of what planners are already doing. In fact, within the context of the CMP, it may useful to make the two processes seamless, at least at the MPOs level.

Therefore, there is a strong case for encouraging planners to be engaged in the development and operation of an LBR program.

Figure 2.1 Steps in the Congestion Management Process

Diagram - Figure 2.1 shows the sequential steps needed to implement the Congestion Management Process. The steps should be integrated with traditional planning activities and products, and should be applied at all spatial scales: project, corridor, and area-wide.

Identified LBR Program

Another option is to establish a defined bottleneck program within the agency. For example, Virginia DOT has implemented the Strategically Targeted Affordable Roadway Solutions (STARS) Program, which is a safety and congestion program that partners state, planning district and local transportation planners, traffic engineers, safety engineers and operations staff to identify “hot spots” along roadways where safety and congestion problems overlap and are suitable for short-term operational improvements. In summary, the STARS program “road audits” are shelf-ready when budget and/or opportunity (e.g., proximity development plans) are available.

Some agencies were originally driven to explore low-cost congestion relief projects because of budgetary restrictions, but soon realized that these projects could be implemented very quickly and, as a bonus, were highly visible and popular with the public. Several DOTs have been able to create a defined bottleneck program area as a result of their success with special initiatives such as these. For example, as a result of their initial success, Minnesota DOT was able to develop a highly accelerated process for bottleneck identification and prioritization, which led to many effective projects in the following two years. Mn/DOT also found that because of lower costs, it could identify multiple locations throughout the region and “spread around” bottleneck reduction projects in a fair and equitable manner. Utah DOT initiated a Choke Point Program in 2006 to address safety, congestion, and bottleneck areas. It was so successful that the Utah Legislature put forth funding for additional chokepoint projects.

Other agencies are developing dedicated LBR Programs in response to FHWA Localized Bottleneck Reduction Workshops held around the United States in 2009 and 2010. These include Indiana DOT and New York DOT.

2.3 Factors for Success: What Does an LBR Program Have to Consider?

The institutional or policy component of localized bottlenecks is extremely important because of the way that agencies and processes have been structured. This is similar to the situation that systems operations and management (O&M) faced 10 to 15 years ago: there was no organizational unit set up to deal with operations and management. As a result, O&M struggled to find an identity in most agencies, and development of O&M programs were hindered. Likewise, LBR programs face institutional and policy barriers. Therefore, one key aspect is to understand the challenges facing agencies in defining a programmatic structure for dealing with bottlenecks. Some of these issues include:

  • Competition for funding with other traditional programs;
  • Implementation issues such as meeting design standards and conformity requirements;
  • Choosing between a temporary, permanent, or periodic (recurring every few years) program for an LBR program;
  • Creating a new organization versus imbedding an LBR program within a current program area (e.g., planning or maintenance); and
  • Developing management support for an LBR.

This section presents success factors for overcoming these challenges in order to implement a LBR program.

Setting Goals and Objectives for an LBR Program

Setting goals and objectives is an important part of framing the establishment of an LBR Program within an agency. The following success factors were identified from case study examples:

  • Relate the goals of the LBR program to the operating objectives of the agency as a whole;
  • Gain the public’s support in targeting and fixing smaller bottleneck issues in a timely manner;
  • Utilize rapid methods to identify and evaluate bottlenecks; and
  • Create separate funding mechanism for bottleneck mitigation or ensure bottleneck projects can compete equitably through traditional methods.

New York DOT’s Region 11 Planning Office (New York City) established their LBR Program with a mission to mitigate recurring congestion at selected chokepoints along the region’s highways, local streets, and intersections, and the operational influences that cause them. Their goal was to investigate the opportunities as well as develop measures for the application of operational and low-cost infrastructure improvements to address chokepoints and to identify cost-effective improvements either as stand-alone initiatives or as part of existing Capital Projects, with an overall objective of moving project recommendations into the capital program.

Championing an LBR Program

The need and urgency for establishing a LBR Program is not always shared across all levels of an agency. Nevertheless, a clear case must be established with upper management and elected officials to secure resources and commitment to proceed with LBR activities.

One way to accomplish this is to demonstrate the return on investment to the organization regarding the implementation of an LBR Program, as well as developing a sustainable approach for assessing the impacts of LBR improvements.

For example, in developing their structured Bottleneck Reduction Program, Michigan DOT’s Systems Operations and Management (SOM) Section sought to obtain leadership support by requesting a dedicated funding template specifically for bottleneck reduction projects. MDOT does not have any dedicated funding at this time, but it is being discussed. They have developed a systematic approach for demonstrating excellent benefit-to-cost ratios among Bottleneck Reduction projects, which helped to justify the creation of the statewide Bottleneck Reduction Program. MDOT is performing analysis on existing road improvement projects so recommendations can be implemented within the existing projects until dedicated funding is approved.

Other ways to raise visibility include:

  • Appointing one element (person or office) within an organization that is the single point of contact and champion for the LBR program. Having a sustained champion can greatly enhance the effectiveness of the program within an organization.
  • Involving the public in identifying bottlenecks is another way to raise the visibility of the program while at the same time building momentum within the organization.

Personnel/Unit Responsible for the LBR Program

The roles and responsibilities for planning and operations usually fall within separate and distinct departments within a typical state DOT. Coordination between departments can improve how an agency tackles bottleneck congestion. A review of state DOTs that have successfully implemented LBR programs within their organizations revealed that having an interdisciplinary team or committee responsible for administering the LBR program is a useful consensus building tool. These teams would facilitate activities of mutual interest such as:

  • Identifying strategies to address bottlenecks;
  • Developing bottleneck performance measures that are consistent across the agency;
  • Coordinating data collection and developing tools for data analysis;
  • Developing models to quantify the impacts of bottleneck strategies; and
  • Overseeing implementation of bottleneck mitigation strategies and objectives through the TIP or LRTP.

For example, New York DOT’s Region 11 LBR Program is administered through an interdisciplinary project scoping team headed by the Planning Director, but whose members are comprised of staff from other functional groups within the agency. Such an approach is a useful tool for building consensus on the nature of transportation problems, the key issues, and best strategies to address bottlenecks. It also creates a forum for early buy-in of preferred alternatives and courses of action across each of the various functional groups.

Indiana DOT is establishing their LBR Program as part of an overall organizational change as they transition to a new funding system that is asset management based with multiple funding teams. As part of the new structure, they are establishing a Mobility Asset Team.

LBR Program Funding

This section presents success factors and examples of how states/MPOs have funded LBR projects. Options include:

  • Developing a funding decision matrix where bottleneck countermeasures compete for funds alongside other mobility and congestion management projects based on benefit-to-cost ratio;
  • Funding low-cost improvement projects as part of a dedicated signal timing program; and
  • Implementing a dedicated program to provides funding for districts/regions to implement low-cost improvement projects.

For example, the Mobility Asset Team (described shortly above) at Indiana DOT will fall under the LBR funding category. INDOT expects that bottleneck countermeasures will have a very good benefit-to-cost ratio and projects will be competitive in the funding decision matrix that is part of the new funding system.

In 2008, Ohio DOT initiated a new Systematic Signal Timing Program that provides district offices and local governments with technical assistance (task order consultants) to analyze, coordinate, and upgrade the timing and phasing of signal systems in high-crash areas. Funding can also be used to upgrade signal equipment as needed. Funding is targeted to those areas listed as a top crash priority by ODOT, MPOs, or local governments. Project sponsors must verify that the crash patterns are relevant to signal timing concerns. Funding requests are funneled through the appropriate ODOT district office, which typically must concur with the request for assistance.

Funded by the Utah Legislature, the Utah Department of Transportation (UDOT) initiated a Choke Point Program in 2006 to address safety, congestion, and bottleneck areas. It was successful, so the Legislature put forth more funding for additional chokepoint projects. The UDOT has used the Choke Point Program to identify potential projects that could improve operations and safety with relatively low cost and in a short time period.

Pennsylvania has in place a Congestion Corridor Improvement Plan (CCIP) which provides funding for districts/regions to study low-cost improvements. However, this program has not been funded since 2008. It is hoped that the program will be resumed whenever funding is available.

The LBR Planning Process

Planning for localized bottleneck improvements includes a number of steps that could happen in a number of ways. But regardless of the approach, they can be loosely organized into the following five broad steps:

  1. Bottleneck Identification;
  2. Identify Bottleneck Improvement Strategies;
  3. Prioritize Projects;
  4. Programming and Implementation; and
  5. Evaluate Bottleneck Improvement Projects.

The remainder of this section expands on each of these steps. Later in Section 2.0 of this document, the unique approaches an agency could take in starting their own LRB program are presented but they are all variations on these steps.

Bottleneck Identification

There is a variety of methods for bottleneck identification. One of the primary methods is a data-driven approach, where roadway characteristics data are used to identify chokepoint locations. Potential data sources include ITS data from traffic management centers, or roadway characteristics and traffic data from statewide traffic and HPMS monitoring locations. Traffic analysis tools can be used to systematically identify bottleneck locations by analyzing road segments for congestion or poor levels of service. For example, at Caltrans, system monitoring and evaluation using the Performance Monitoring System (PeMS) is seen as the foundation for the entire Corridor System Management Plan process because it cannot only identify congestion problems, but can also be used to evaluate and prioritize competing investments.

Bottleneck locations can also be identified anecdotally by tapping into local agency knowledge and personal experience (e.g., district-level), direct observation of local agency personnel, aerial photographs, or video surveillance data. For example, when Michigan DOT solicited potential bottleneck locations, they were sure to include problem descriptions from each of their seven region offices and not merely their headquarters’ analysis. More than 200 locations were identified, with about one-third being freeway interchanges.

There is a hybrid approach where anecdotal information and judgment is used to identify candidate locations but data are used to assess priorities objectively. For instance, the following conditions typically exist or help to identify a recurring bottleneck condition:

  • A traffic queue upstream of the bottleneck, wherein speeds are below free-flow conditions elsewhere on the facility.
  • A beginning point for a queue. There should be a definable point that separates upstream and downstream conditions. The geometry of that point is often coincidently the root cause of the operational deficiency.
  • Free flow traffic conditions downstream of the bottleneck that have returned to nominal or design conditions.
  • As it pertains to an operational deficiency, a predictable recurring cause.
  • Traffic volumes that exceed the capacity of the confluence to process traffic. (Note: This applies to recurring events even more so than nonrecurring.)

Some metropolitan areas have even conducted public outreach efforts to solicit input from motorists on bottleneck locations. For example, Metroplan, the MPO for the Little Rock, Arkansas region, conducted Operation Bottleneck during the fall of 2008, a public outreach effort designed to identify traffic bottlenecks, as well as automobile, bicycle, and pedestrian safety issues throughout the region. The program received 3,000 responses within two months, with on-line submissions constituting the highest return. Several minor roadway improvements have already been completed or are planned as a result of the program.

Bottleneck Improvement Strategies

This section describes the types of LBR treatments, as well as a matrix on matching bottleneck treatments to needs. It also describes various barriers to implementing LBR treatments such as design standards/exceptions, air quality conformity, and consistency with long-range design concepts.

Types of LBR Treatments

The following is a sampling of short-term, low-cost operational and geometric improvements. All of these remedies address operational deficiencies, as opposed to other congestion mitigation efforts that address driver choice, travel demand, corridor-wide upgrades, or simply (but expensively) building our way out of congestion.

  1. Shoulder conversions. This involves using a short section of traffic bearing shoulder as an additional travel lane. Shoulder conversions are appropriate between interchanges or to provide lane congruency with adjacent sections. The shoulder condition should be rated for use as a travel lane.
  2. Restriping merge or diverge areas to provide additional lanes, provide an acceleration/deceleration lane, extend the merge/diverge area, or improve geometrics to better serve demand.
  3. Lane width reductions. This involves reducing lane widths and restriping to add an additional travel and/or auxiliary lane.
  4. Modify weaving areas by adding collector/distributor or through lanes.
  5. Ramp modifications. These could include ramp metering; widening, extending, closing, or consolidating ramps; or reversing entrance and exit ramps to improve operations.
  6. Speed harmonization (variable speed limits). This is the practice of adjusting speed limits when congestion thresholds have been exceeded and congestion and queue forming is imminent. Speed harmonization can also be used to promote safer driving during inclement weather conditions. This mostly European practice reduces the traffic “shock wave” that results through congested corridors, thereby delaying the onset of a breakdown in traffic conditions. The result is decreased headways and more uniform driver behavior, which indirectly benefit bottlenecks and chokepoints.
  7. “Zippering” or self-metering that promotes fair and smooth merges. A motorist who is 10th in line knows that he will be 20th to merge into the single lane ahead. This helps to eliminate line jumpers that bull ahead, disrupt the queues, and often block adjacent lanes until they force their way in line. Usually this method of merging requires on-site enforcement, but often is exhibited by regulars who know the process and are willing to abide.
  8. Improve traffic signal timing on arterials. Also, traffic signal timing improvements at ramp terminal intersections will prevent ramp queues from backing up onto freeway main lanes.
  9. Access management principles to reduce vehicular conflicts (hence, delays) on arterial corridors
  10. Continuous flow intersections. These are unconventional at-grade intersections, which eliminate one or more left-turn conflicts at a main intersection. This is achieved through dedicated left-turn bays located several hundred feet prior to the main intersection, which allow left-turning vehicles to move at the same time as through traffic. The left-turn traffic signal phase is eliminated, allowing more vehicles to move through the main intersection and thus reducing traffic congestion and delays. These at-grade intersections achieve traffic flow similar to grade-separated interchanges, but at a considerably lower cost.
  11. High-Occupancy Vehicle (HOV) or reversible lanes.
  12. Provide traveler information on traffic diversions.
  13. Implement congestion pricing. Congestion pricing entails charging fees or tolls for road use that vary by level of vehicle demand on the facility. The objective is to bring supply and demand into alignment.

Matching Bottleneck Treatments to Needs

In 2006, as part of the research conducted for National Cooperative Highway Research Program Project 3‑83 (“Low-Cost Improvements for Recurring Freeway Bottlenecks”), a series of interviews was conducted with state and local transportation agencies to assess the effectiveness of low-cost improvements used at bottleneck locations within their jurisdictions. The results showed that agencies are using a wide range of strategies to improve bottlenecks, many of them low-cost improvements that can be implemented quickly. The most frequently used operational improvements were ramp metering, auxiliary lanes, and HOV lanes.

Some of the key questions and considerations when selecting improvement alternatives for bottleneck removal include:

  • Is there an inside shoulder that would create a usable traffic lane for a short section of freeway?
  • If a shoulder is considered for conversion, is there right-of-way (ROW) to allow adding one back for part of the length of the project?
  • If there are bridges, are they wide enough to accommodate the extra lane while allowing adequate clearance to barriers (2 feet) and an outside shoulder? If not, are they short enough that a loss of shoulder as a breakdown lane would not be critical (500 feet or less)?
  • If changes to an entrance or exit ramp or weaving area are considered, will adjusting the position of ramp gores cause geometric problems which must be resolved?
  • Are vertical clearance issues, grade-matching, and sight distance problems created?
  • If the bottleneck movement itself cannot be fixed reasonably, can the other traffic which is affected by it be better accommodated?
  • Finally, will the improvement invite enough new traffic to cause immediate breakdown again or is this truly the clearing up of a “kink” in the system, without being a capacity addition that will overload some other part of the facility?

Barriers to Implementing LBR Treatments

Because some bottleneck treatments involve innovative solutions that maximize effectiveness with a minimum of new construction, they are occasionally at odds with highway design standards. A design exception may be required. For example, the addition of slip ramp to a collector/distributor road or the use of a shoulder as a through lane at selected locations may not strictly follow allowable design standards. Such deviations have the potential to degrade safety if not properly implemented; the elimination of a shoulder may lead to more collisions with roadside features or may impede incident management activities. As it is FHWA’s intent to foster creative approaches for low-cost bottleneck improvements, agencies should not see the design standard issue as insurmountable. Rather, they should fully assess the potential safety impacts of strategies and devise ways of addressing them, if necessary. For example, in the case of a shoulder-to-lane conversion, review of crash data, and the specific roadway location (perhaps through a Roadway Safety Audit), it may be determined that a barrier is required to keep vehicles off of the roadside. It may also require a change in incident management policy that would allow emergency vehicles to access incidents from the opposite direction. Finally, agencies should be in contact with the FHWA Division offices throughout the process as design review may be required, depending on circumstances.

The second potential issue relates to air quality conformity. Because they are short term in nature, localized bottleneck improvements may emerge as formal projects that have not been previously identified in Statewide Transportation Improvement Programs or MPO-generated Transportation Improvement Programs. Thus, they may not be part of those projects that have been approved to deal with air quality issues in the region or state. Such occurrences must be dealt with on a case-by-case basis by agencies wishing to undertake bottleneck improvements. One point worth noting: if air quality conformity in a location precludes or discourages major capital expansion (e.g., additional lane-miles), the type of improvements in a localized bottleneck program clearly do not fall in this category.

Finally, another potential barrier is that bottlenecks may not be seen as consistent with Long-Range Design Concepts. As discussed previously, most bottleneck mitigation strategies such as roadway widening, left-turn lengthening, auxiliary lanes on freeway, or improvement of weave/merge areas may all be seen as distracting resources from larger design solutions, which will be made anyway in a larger longer-term project already in a 20-year plan. Agencies must decide and weigh the benefits themselves whether the cost of doing a smaller bottleneck solutions in the short terms against the cost of waiting for a more complete solution.

Bottleneck Assessment/Analysis Methods

Once bottleneck locations have been identified, the root cause and severity must be determined. Special travel time runs, aerial photography, or video of suspected bottleneck areas can be used to pinpoint sources of operational deficiencies. On freeways equipped with detection technology, dynamic surveillance can be used to identify where and how often bottlenecks occur, and how severe they are. Archived traffic data can be used to measure whether the problem is growing or receding.

Sometimes, the operational cause of a bottleneck is evident, intuitive, or anecdotal. However, when multi-mile corridor congestion is prevalent, microsimulation modeling can assist in identifying, separating, and analyzing bottleneck dynamics within the corridor.

Bottleneck analysis is necessary to study not only the subject location, but also the impacts of potential bottleneck remediation on upstream and downstream conditions. The analysis will justify action to correct bottlenecks, confirm the benefits of bottleneck remediation, or check for hidden bottlenecks along a corridor. When conducting bottleneck analysis, care should be taken to ensure that:

  • Improving traffic flow at the bottleneck location does not just transfer the problem downstream. The existing bottleneck may be “metering” flow so that a downstream section currently functions acceptably, but the increased flow will cause it to become a new bottleneck.
  • Future traffic projections and planned system improvements are inclusive in the analysis. Safety merits also should be strongly considered.
  • “Hidden bottlenecks” are considered. Sometimes, the queue formed by a dominant bottleneck masks other problems upstream of it. Improving the dominant bottleneck may reveal these hidden locations. It is important to take into account the possibility of “hidden bottlenecks” during the analysis stage.
  • Conditions not traditionally considered by models are accounted for. There are several bottleneck conditions, such as certain types of geometrics and abrupt changes in grade or curvature, that cannot be analyzed by current analysis tools. Engineering judgment will need to be exercised to identify those problems and possible solutions.

For example, New York DOT’s Region 11 LBR Program is comprised of an interdisciplinary team headed by the Planning Director. The LBR Team compiles various completed studies and will bring other agencies on board as needed in order to develop a current inventory of bottleneck locations citywide; develop screening criteria; select and recommend priority locations for improvements; develop strategies for the selected locations and prepare the implementation plan. Projects are selected based on the following screening criteria: 1) project cost less than $10M; 2) annual vehicle-hours-delay > 25,000 hours; 3) speeds < 30 mph; 4) requires little or no environmental documentation; and 5) projects NOT already programmed in the TIP. The LBR Team works with Program Management to address project programming, funding, and schedule issues, and they coordinate with local MPO staff regarding any TIP and/or conformity issues. As the work of the LBR program becomes better defined and develops greater focus, the team will expand to include other external agencies as well.

In Utah DOT’s Choke Point Program, potential projects are identified through public observations in the regions and input from users and local governments. Potential projects are then selected and prioritized based upon several factors, including average annual daily traffic (AADT), volume to capacity ratio (V/C), constructability, region priority, and accident rates. Qualifying criteria for potential projects include: 1) small safety, capacity or bottleneck projects that cost less than $10M; 2) can qualify for a categorical exclusion; 3) can be designed and constructed within one year; and 4) require minimum right-of-way needs. Examples of chokepoint projects include roadway widening, left-turn lengthening, dual left-turns, auxiliary lane on freeway, intersection or signal improvement, passing lanes on rural routes, and improvement of weave/merge areas.

Evaluating Bottleneck Improvement Projects

After implementation, it is often beneficial to conduct an “after” evaluation to gauge the effectiveness of the bottleneck removal project. A conservative approach to evaluating treatment effectiveness is to evaluate operational and safety benefits achieved. Common evaluation methods include microsimulation modeling, benefit/cost analysis, and crash data analysis using data collected before and after project implementation. In addition, the following performance measures are often used to assess the effectiveness of bottleneck improvement strategies: average speed (travel time), lane density, queue lengths, queue discharge rates, vehicle miles of travel (VMT), and vehicle hours of travel (delay). Additional insight could be obtained from before and after opinion surveys of area drivers. These types of evaluations are often not done, yet are important to quantify the benefits achieved through bottleneck mitigation.

Bottleneck Performance Measures in Bottleneck Assessment and Evaluation

This section describes bottleneck performance measures, data and methods needed to develop the metrics, presentation of performance measure results, and matching bottleneck treatments to needs.

Metrics

There are a number of metrics, which could be used to identify and track the results of bottleneck mitigation strategies. Below is a list developed by the /Mn/DOT.

  • Percentage of miles congested (i.e., number of directional miles with speeds < 45 mph during peak periods);
  • Total daily delay (volume x time difference between actual and posted speed);
  • Reliability (TTI – Congestion Index/Travel Time Buffer Index);
  • Miles of FIRST/incident response coverage;
  • Number of hours where volume > capacity;
  • Frequency of signal retiming;
  • Percent of arterials with coordinated signals;
  • “Before/After” benefit/cost ratio of corridor improvements;
  • “Before/After” benefit/cost ratio of signal retiming;
  • Customer satisfaction survey of peak-hour travel(omnibus transportation survey);
  • Percent of MUFS instrumented;
  • Planned lane closures System;
  • Unplanned lane closures System;
  • Average clearance time for snow and ice removal;
  • Average clearance time for freeway incidents; and
  • Throughput (i.e., number of vehicles through a specific corridor or across a screenline over a specified time period).

Data and Methods Needed to Develop Metrics

Data collection to support bottleneck analysis should be sufficient to capture the duration and extent of congestion. Typically, 15-minute traffic volume counts for all ramps and main lanes for a four-hour peak period are adequate. Other data can be collected through travel time runs, video, or origin-destination studies. Many regional TMCs are archiving the data from their systems and can be a very helpful resource.

Presentation of Performance Measures

Performance measures can be presented in a number of formats. The one recommended for this effort include routine reports on an annual or semiannual basis. If more frequent reporting is required, many emerging on-line reporting tools are becoming available that provide robust dashboard style results to easily convey to leadership and the public the status of a bottleneck program.

2.4 Bottleneck Self-Assessment

Table 2.1 describes procedures for agencies to conduct an LBR Self-Assessment to establish where they currently stand with regard to implementing a bottleneck program, perhaps to the level of identifying at which “stage” it is.

Table 2.1 Bottleneck Programming Maturity Model Matrix
Level 0 – Ad Hoc 1 – Aware 2 – Planning 3 – Defined 4 – Managed 5 – Integrated 6 – Continuous Improvement
Institutional No structured LBR Program in place. Some level of bottleneck recognition. Agency is discussing needs/plans for a structured LBR program. Development of a formal LBR program is underway. Development of a formal LBR program is underway. A formal LBR program is named and established, either as a separate program or part of another program. Empty cell
Organizational No LBR Program Champion or Team in place. Agency is aware of the need for a LBR Program champion and Team to support LBR activities. Some level of LBR program assessment and formulation of roles for LBR Team is underway in one or more offices of agency. Some level of LBR program assessment and formulation of roles for LBR Team is underway in one or more offices of agency. Some level of LBR program assessment and formulation of roles for LBR Team is underway in one or more offices of agency. Specific staff have the responsibility for oversee a formal LBR program. Empty cell
Planning/Programming LBR strategies are not included in agency planning/programming processes. Agency has developed procedures for considering LBR strategies in the planning and programming processes. Agency has developed procedures for considering LBR strategies in the planning and programming processes. LBR strategies becomes a component of the CMP. LBR strategies integrated with short- and long-term planning and programming. LBR strategies appear in planning and programming documents: MPO TIP, LRTP, annual programmed projects list. Empty cell
Performance Measures No defined practices and techniques for bottlenecks. Agency has produced a set of procedures for measuring performance of bottlenecks (evaluation procedures). Agency has produced a set of procedures for measuring performance of bottlenecks (evaluation procedures). Selected LBR projects are evaluated. LBR projects are routinely evaluated. LBR projects are highlighted in agencywide reports of congestion and safety. Empty cell
Assessment/Analysis Tools No defined tools to support bottleneck assessment/analysis process. Agency has defined procedures for identifying and assessing LBR strategies. Agency has defined procedures for identifying and assessing LBR strategies. Agency has defined procedures for identifying and assessing LBR strategies. Agency has defined procedures for identifying and assessing LBR strategies. A combination of analytical methods are used at different stages of LBR assessment and evaluations. Empty cell

2.5 Templates for Getting Started

This section introduces three templates that transportation agencies can consider in developing their own LBR Program. Each template includes an overall description of the approach, a bullet list of the key elements of the approach, followed by a step-by-step guide to implementing the template. Finally, each template concludes with a real-world example of the approach discussed.

The following templates are included in Appendix A.

  • Template #1: Public Outreach Identification Process;
  • Template #2: Leverage Existing Non-Bottleneck-Related Processes; and
  • Template #3: Internal Identification Processes.

2.6 Sustaining a Successful Program

Once a LBR program has been established, its ongoing success will be based largely on two factors, funding and institutional integration. If funding for LBR programs is either dedicated or at least available through traditional sources, the chances that LBR issues will be considered in the future is very high. If, however, an agency goes through the initial effort of setting up a LBR program and is at the end of the process unable to secure dedicated funding, or at least access to traditional sources, the program will not remain viable. It is, therefore, critical that agencies consider funding options early on in the process. That is not to say LBR effort should not be initiated without funding secured; just the opposite. Many times the effort of setting up the LBR program can build enough momentum within an organization to secure funding or at least ensure access to compete with for funding.

Likewise, sustaining an LBR program will be much easier if the program is integrated into an organization. If identifying and evaluating LBR projects can become part of the core mission of the agency, the LBR program will continue even after the initial champions have left the organization or been reassigned.

2.7 Signs of a Latent Program

It may be prudent here to take a moment and discuss “when is a program not a program,” that is to say, when a program has de-evolved to not-producing effective mitigation projects.

Certainly, there are some administrative actions that would annul any active program. Foremost among these would be budget cuts, new administration initiatives, and emergencies. But in context of recognizing a dormant localized congestion mitigation effort, here are some vital signs to check.

  • Projects are not being produced under “low-cost, short timeframe” measures. The LBR program specifically does not define these terms in the context of the program; however, if projects are not being completed within “annualized” budgets, or are not being delivered in relatively short timeframes (e.g., a “construction season” as opposed to multiple out-years) then chances are these projects are outside the de facto definition of a “localized” congestion mitigation project.
  • Candidate project lists are drying up. If a pre-standing list of candidate mitigation locations either does not exist or has not been updated for some time, then it may be a sign that program momentum has lapsed.
  • Is the work effort generally equitable to the project size? Generally speaking, low-cost, short-term projects should have a much smaller planning and execution effort than large projects. By their very nature, these projects should be quick turn-around, low-cost, and high-yield benefits. However, if the project is bogged down with overly lengthy studies (“paralysis by analysis”), add-ons, or cost escalations, then it may be a sign that said project is beyond the scope of “localized.”

All of the above signs of a latent program are further discussed in FHWA’s “Traffic Analysis Toolbox X: Localized Bottleneck Congestion Analysis” (FHWA-HOP-09-042) which focuses on what level of analysis is appropriate and representative for the subject projects and programs. In summary, that document concludes that the level of analysis (of any problem) should roughly correlate to the size of the problem. The main questions that this guidance helps an agency frame are: 1) do we have a satisfactory agency methodology to specifically address localized congestion problems; 2) within that program, do we have satisfactory justifications for project candidacy, selection, and solutions for said problems; and 3) are we executing these projects in a timely fashion and within budgets that are representative of the context of a “Localized Bottleneck Reduction” program?

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