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Integrating Business Processes to Improve Travel Time Reliability (2011)

Chapter: Chapter 4 - Case Studies: Work Zone Management

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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
×
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
×
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
×
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Suggested Citation:"Chapter 4 - Case Studies: Work Zone Management." National Academies of Sciences, Engineering, and Medicine. 2011. Integrating Business Processes to Improve Travel Time Reliability. Washington, DC: The National Academies Press. doi: 10.17226/14510.
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C H A P T E R 4 Case Studies: Work Zone ManagementWork zones in the United States account for approximately 10% of congestion, according to research from the FHWA (1). Work zones are defined as any construction activities that result in physical changes to the highway environment, such as reductions in the number or width of travel lanes, lane shifts, lane diversions, and temporary road closures. Work zones often reduce capacity and may experience higher crash rates than other segments of freeways, thereby contributing to a decrease in reliability. Furthermore, longer-term closures for major construction projects often have shifting impacts as traffic control strategies are modified to respond to changing schedules or unforeseen issues in the field. This section presents case studies that examine the processes that the North Carolina DOT (NCDOT) and Michigan DOT (MDOT) have used to better manage work zones. The NCDOT Traffic and Safety Operations Committee is tasked with eval- uating work zones before any significant changes or when crash rates and speeds increase in the work zones. In Michi- gan, MDOT transportation planners have used microsimu- lation modeling to evaluate traffic control plans and select the plans based in part on their impact on the overall transporta- tion network. North Carolina: NCDOT Safety and Traffic Operations Committee NCDOT has implemented an interagency coordination process for the planning and monitoring of major construction work zones. The coordination process begins before construction, ideally in the planning stage, and is continued throughout the project. The process is determined by the needs of each unique construction project. Initially, internal planning level meet- ings are conducted to establish the scope of a work zone. A project-specific Safety and Traffic Operations Committee is created to oversee the implementation of a work zone. This process is focused on addressing the work zone safety and35mobility requirements provided by FHWA, 23 CFR Part 630, Subpart J. In preparation for this case study, a discussion was held with Joseph Ishak, PE, Central Work Zone Traffic Control (WZTC) Section engineer, and Jennifer Portanova, PE, project design engineer, both with NCDOT. The following information rep- resents their knowledge based on specific project experience. Description This case study was selected based on the proactive approach to managing the impacts of the project work zone and the con- tinuous coordination between several involved agencies. The NCDOT Safety and Traffic Operations Committee is com- posed of representatives from the WZTC Section, the NCDOT field office, safety engineers, incident management personnel, public safety agencies, North Carolina State Highway Patrol (NCSHP), the public information representative, and the con- tractor. These representatives coordinate to ensure the safety of the workers and travelers, as well as the efficiency of the work zone and the transportation network. The NCDOT Safety and Traffic Operations Committee focuses on significant projects as defined by the Work Zone Safety and Mobility Policy, where mobility and potential safety concerns exist. This allows the committee to provide better focus and attention to those construction projects, which will allow them to have the greatest positive impact. NCDOT guidelines clearly define four activity levels of significance. The criteria for determining the level of significance include lane closures, annual average daily traffic (AADT), truck traf- fic, additional travel times expected, level of adverse impacts to existing transportation infrastructure/high-volume traffic gen- erators, duration of traffic impacts and user value or cost. The coordination process and committee involvement are then based on the determined level and specific needs of the project. Coordination for the concept, design, implementation, and monitoring of work zones occurs throughout the life of

36a construction project, with varying levels of participation. The early planning stages for the traffic management concept of a project only involve units internal to NCDOT. As the project continues to later phases of the design, through implementa- tion and monitoring, a committee is established with stakehold- ers specific to the project area. The committee has an active role in implementing and monitoring safety and traffic operations in conjunction with each major lane shift or when increases in crash rates or speeds are observed. As an extension of this col- laboration process, the NCDOT Work Zone Traffic Control Section, which is part of the Mobility and Safety Division, has initiated an effort to continually monitor and evaluate the effectiveness and safety of work zones. Based on observed conditions, the committee can initiate speed or safety studies to validate concerns in the vicinity of the construction proj- ect. The resulting information is available to guide decisions aimed at revising and improving the existing traffic manage- ment plan. The Safety and Traffic Operations Committee also consid- ers the impacts of the project work zone on the surrounding network and seeks to efficiently plan for and minimize those impacts where possible. Lane and ramp closures are carefully considered because of their impact on the surrounding net- work. In addition, modifications or improvements to spe- cific segments of the network may be recommended to handle the additional traffic resulting from the construction project. Since the inception of this coordination process, the com- mittee has been responsible for managing the planning and monitoring of work zones for several significant projects. Some construction projects have been completed with no major crashes or fatalities. Background of Agency The NCDOT Traffic Management Unit is one of six technical units within the Transportation Mobility and Safety Branch. The Traffic Management Unit consists of the Congestion Man- agement Section, the Municipal and School Transportation Assistance Section, and the WZTC. Based on the NCDOT’s mission statement and goals, the WZTC Section is primarily tasked with making the infrastructure safer and more efficient in and around work zones. The WZTC Section regularly coordinates with municipali- ties, highway patrol, emergency responders, other department branches, and other agencies. The WZTC Section is respon- sible for developing traffic management plans that maintain mobility and safety through a work zone. In addition, the per- formance evaluations for each staff member within the depart- ment are directly connected with the department’s goals; staff members are encouraged to evaluate current operations and implement strategies that directly seek to reach these goals. Thefocus of the Safety and Traffic Operations Committee is in line with the established goals as it works to safely and efficiently plan, implement, and monitor the work zones of significant projects. Process Development The impetus for the Safety and Traffic Operations Committee meetings was a fatality that occurred within a construction project work zone. Because of the fatality, a coordination meeting with key stakeholders was conducted. These meet- ings continued throughout the remainder of the project. The collaboration was useful and productive; therefore, when the US-70 Clayton Bypass project was nearing construction, it was decided to hold similar coordination meetings before con- struction, during construction, and before major traffic shifts. The meetings were held to address upcoming traffic shifts, enforcement, speed limits, incidents, public information, and a construction update on the project. The meetings were again successful, and NCDOT created the Safety and Traffic Opera- tions Committee, which is now involved in significant projects and seeks to address the work zone safety and mobility require- ments provided by FHWA, 23 CFR Part 630, Subpart J. Detailed Process NCDOT has published Guidelines for Implementation of the Work Zone Safety and Mobility Policy, which outlines the goals, objectives, and strategies for all projects and identifies key stakeholders who are responsible for the implementation of each objective (2). The document also provides a method of determining the project level of significance, which, in turn, determines the required management practice. Projects that are determined to be significant within the guidelines require the establishment of a Safety and Traffic Operations Com- mittee composed of representatives from the agencies out- lined above. The Safety and Traffic Operations Committee meetings are conducted to evaluate the impact of the work zone on traf- fic on the major routes. Meetings are conducted before the implementation of the traffic management plan and continue throughout the life of the construction project. Corridors are designated as major routes based on the project location and the perceived regional impact of the work zone. Instead of conducting monthly scheduled meetings, the meetings are established based on key milestones of the project and when certain issues are identified within or in the vicinity of the work zone. The milestones include scheduled traffic shifts or changes in the work zone that can result in major impacts on traffic. The work zone plans are reviewed for effectiveness based on observed conditions in the work zone. The field personnel,

37contractor, and law enforcement agencies provide input into the actual traffic conditions experienced in the work zone. Increases in speed, increases in crash rates, and other negative trends observed are discussed at the meetings and possible solutions are presented. The committee coordinates to identify viable mitigation strategies in response to the issues observed in the work zone. Possible solutions include ramp closures, added presence of law enforcement, or restrictions in the contractor’s available working hours. The strategies are implemented and continu- ally monitored for effectiveness until other negative trends are identified or the construction project is complete. Suc- cessful implementation of effective strategies also can lead to policy-level changes to guide future traffic management plans and work zone implementations. An example of the process used by the Safety and Traffic Operations Committee is shown in Figure 4.1.Figure 4.1. Detailed business process diagram of NCDOT Safety and Traffic Operations Committee.Several key integration points were identified in the NCDOT Safety and Traffic Operations Committee process, including the following: • Integration between the NCDOT Division Office, the NCDOT Work Zone Traffic Control Section, and the con- tractor to review work zone traffic control plans; • Integration between NCDOT, the contractor, and the NCSHP to review final plans before implementation; • Integration between NCDOT and the contractor for revised work zone plans before implementation; • Integration across all players to monitor performance of the work zone once implemented; • Integration between agencies to review potential solutions when issues are identified and implemented; and • Coordination with North Carolina’s Information Manage- ment Public Affairs, Construction and Traffic Control

38(IMPACT) group for public information assistance to pro- vide outreach and information specific to the work zone. Integration also is encouraged because of the required traf- fic management plan process. The WZTC Section must pro- duce traffic management plans for every construction project on NCDOT-maintained roadways. Any modification to the work zone must be based on traffic control plans sealed by a professional engineer. Each time there is a change, a new set of plans are developed and sealed. As modifications are made in the field, it is important for the changes to be documented in the existing plans. It also is important that detailed meeting minutes are captured for each Safety and Traffic Operations Committee meeting. Since the work is occurring in an active work zone, the resident engineer should maintain these records through the construction life of the project and as long as state law requires. Types of Agencies Involved The Safety and Traffic Operations Committee includes partic- ipants with a vested interest in maintaining a safe and effective work zone. The NCDOT WZTC Section is responsible for the design and management of work zones for all roadway projects across North Carolina. The NCDOT Division is responsible for the construction of the roadway projects and works closely with the WZTC Section on issues or questions regarding the work zone traffic control plans. Additional stakeholders include local agencies that can be affected by rerouted traffic, emergency management services and emergency responders who need uninterrupted access to the work zone during inci- dents, the Traffic Systems Operations Unit that oversees pub- lic information for larger construction projects and manages the statewide incident management and traveler informa- tion systems for 511 and the web, Traffic Safety Unit, and the NCSHP that is responsible for law enforcement on North Carolina’s highways. These stakeholders collaborate through the Safety and Traf- fic Operations Committee, which provides opportunities to develop relationships and trust. The committee establishes a network of informed individuals who seek to provide the public with safe and reliable transportation throughout North Carolina. The relationships and networks that are established carry over into other aspects of the transportation network as well. For example, through efforts to successfully imple- ment tougher penalties for speeding through work zones, the NCDOT has developed a strong relationship with the NCSHP. This relationship and foundation of trust has carried over into the Safety and Traffic Operations Committee. The committee also provides the contractor with another avenue to seek direction and communicate concerns. The con- tractor is driven by a need to construct the roadway project onschedule and under budget while maintaining a safe work envi- ronment for its employees. Since larger construction projects can include daily liquidated damages for delayed completions, the contractor is always focused on efficient and safe operations within the work zone. The contractor is aware of daily experi- ences in the work zone and can identify unsafe scenarios within the work zone and when traffic patterns, such as increased speeds, begin to change. The contractor coordinates with field personnel on a daily basis, but the Safety and Traffic Opera- tions Committee provides a means for the contractor to com- municate concerns with the WZTC Section, NCSHP, incident management, and public information personnel. The committee establishes relationships and networks of informed individuals that build trust with their partners to reach a common goal. These partnerships increase the safety and mobility of work zones for significant projects throughout North Carolina. They also influence coordination among the same agencies that may communicate on other transportation projects. Types of Nonrecurring Congestion Addressed As stated, work zones are categorized as planned events, but can generate long-term effects on traffic. Work zones modify the roadway operations for specific time periods, and these modi- fications must be evaluated to minimize impacts to mobility, safety, and travel time reliability. The NCDOT Safety and Traf- fic Operations Committee is focused on continually monitor- ing the effect of a work zone on the roadway capacity. The committee also plans for secondary incidents and considers how emergency responders can efficiently respond within the work zone. Additionally, construction contracts specify that the contractor will be required to clear incidents in a set amount of time and requires that a towing company be identified within the contract as a subcontractor. Not only does the committee consider potential incidents, but it also attempts to minimize the incidents that occur by carefully establishing the appropriate speed limits within the work zone. Higher work zone speeds increase the safety risks for the motorists and workers in both quantity and severity. Higher speeds, increased crash rates, and ineffective lane shifts have a direct impact on travel time reliability within the work zone. The committee has established a process to identify, evaluate, and implement mitigation strategies to offset nega- tive impacts on travel time reliability and these strategies have proven successful in recent projects. Performance Measures The committee has identified specific performance mea- sures, such as speed and crash rates, to continually evaluate the safety and mobility of the work zone. When these measures

39demonstrate negative trends, the committee works to address issues that promote the variation in driver behavior. The changes in trends can be identified by any of the committee participants, including the resident engineer, contractor, and even the NCSHP. Once a mitigation strategy has been imple- mented, the safety and mobility of the area are monitored to ensure that the strategy has been effective and does not gen- erate more problems, such as an increase in congestion. As an example, the committee recently managed an I-40 project that had no fatalities in the work zone throughout the construction project and a decrease in the crash rate on the corridor during the project. The committee feels that the reduction in the crash rate can be attributed, in part, to a com- bination of the proactive management of the work zone, a higher level of law enforcement, and extensive outreach to inform the public of the project. Benefits The Safety and Traffic Operations Committee has developed greater trust and partnership between contractors, NCDOT, and the NCSHP. Working toward a common interest of improving safety for workers and motorists has strengthened the trust developed between the multiple agencies. The com- mittee provides a means to evaluate traffic management plans before implementation and during construction. The continu- ous monitoring of the work zone provides a safer work environ- ment and roadway. Modifications to the traffic management plan can be easily implemented because everyone is continu- ally involved. Additional benefits and increased efficiencies are experienced through targeted enforcement on areas within the work zone where safety issues and a higher rate of violations are observed. Lessons Learned The committee has seen great success on the few projects where a traffic management plan has been implemented. The success is based on established trust between the partners and docu- menting the safety and mobility of work zones. This trust is established through targeted meetings that are held only when needed and involve the correct stakeholders. Documenting the impacts of work zones will provide reference points for deci- sions made on future traffic management plans based on well- documented successful practices. Analysis and Research Observations The process has provided a means by which all affected stake- holders can provide continuous feedback concerning the effec- tiveness of a traffic management plan. On typical construction projects, stakeholders are involved to a certain degree duringthe plan development, but implementation and monitoring of the work zone is handled by the division and contractor with some coordination from the WZTC Section. The establish- ment of the Safety and Traffic Operations Committee allows any affected stakeholder to voice concerns about the work zone and traffic control plan at any point during the construction project. Committee meetings allow identified issues to be presented and resolutions to be discussed because each of the stakehold- ers provides a specific focus for the work zone. Having a discus- sion about potential solutions with all the stakeholders allows each partner to voice concerns that could affect their particular focus area. For example, a full ramp closure could eliminate dangerous weave conditions on the mainline but also may eliminate a key access point for emergency responders to access the roadway. The ramp closure also may eliminate key access to the local municipality. The committee approach to address- ing issues yields the most effective and supported solutions. The continuous evaluation of the work zone evaluates the average speed and crash rates so that problem locations can be identified early and addressed. The attention to observed issues results in greater mobility and safety within the project limits and better travel time reliability on the network. The ability to quickly assemble stakeholders, discuss options, and implement solutions demonstrates an effective approach to mitigating identified issues. The specific focus of meetings also establishes trust with the stakeholders that meetings will be successful and results will be produced. Michigan: MDOT Work Zone Traffic Control Modeling The Michigan DOT I-75 Ambassador Bridge Gateway Project includes the reconstruction of the I-75 and I-96 freeways, a new interchange for the Ambassador Bridge, a redesign of the Ambassador Bridge Plaza, and a pedestrian bridge across I-75 and I-96 to connect east and west Mexicantown in southwest Detroit. The Ambassador Bridge, which connects Detroit, Michigan, and Windsor, Ontario, Canada, is one of the busiest commercial bridges in the world and the largest commercial border crossing in North America, with approximately 11 mil- lion vehicles crossing the bridge each year. It is a vital inter- national trade route and access to the bridge needed to be maintained at all times during the reconstruction. I-75 also serves as a critical link for trade and manufacturing in the Midwest. For Michigan’s large manufacturing industry and their many suppliers along the corridor from Ohio to Ten- nessee, I-75 is a necessary lifeline. Construction started on the I-75 Ambassador Bridge Gate- way Project in February 2008 and was scheduled for completion in fall 2009. As part of the construction, I-75 was scheduled to be closed for 18 months through downtown Detroit and a

40complete closure of the I-75/I-96 interchange was scheduled for three months. To determine the impacts of the closure and plan detours and traffic management strategies, MDOT used large- network microsimulation. The microsimulation model was created on the Paramics model software platform by a consultant. MDOT Metro Region Planning staff and Traffic and Safety staff closely coordinated with the consultant to develop and implement work zone mobility mitigation plans. This case study was based on inter- views with MDOT Metro Region staff. Description This case study examines the modeling process that MDOT used to evaluate the impacts and to develop work zone traffic control plan alternatives. The ability of MDOT to develop network microsimulation models of work zones around the project began years before construction started, with the development of the Southeast Michigan Freeway Simulation (SEMSIM) model on the Paramics platform. SEMSIM was originally developed as a tool for helping facilitate MDOT proj- ect funding decisions for Southeast Michigan. MDOT Metro Region Planning repurposed the SEMSIM model and applied it to work zone modeling of the I-75 Ambassador Bridge Gate- way Project. This marked the first time that network micro- simulation had been used in an operations analysis, as opposed to planning applications. The model also had to take into account numerous other planned closures of I-75 and sur- rounding roads partly because of the I-75 Ambassador Bridge Gateway Project and partly because of other planned freeway and local construction projects (3). The MDOT consultants modeled several scenarios corre- sponding to various project stages. The scenario for the sum- mer of 2008 was most critical because, in addition to the I-75 mainline closure, it included the complete closure of the I-75/I-96 interchange, as well as other scheduled project clo- sures within the Gateway simulation network. The MDOT consultants worked closely with MDOT Metro Region Engi- neering staff, Construction staff, and Traffic and Safety staff, including the Michigan Intelligent Transportation System (MITS) Center, to evaluate various alternatives for construction closures. They eventually came up with a plan that demon- strated congestion would be high, but that the plan would work and could handle the projected traffic volumes. Construction began in February 2008, with the most critical phase occurring in summer 2008, which entailed the complete closure of the I-75/I-96 interchange. During the three months modeled for summer 2008, MDOT found that the traffic and congestion predicted by the model was close to what MDOT was observing in the actual construction work zones. Field conditions on this complex and interdependent free- way network often unexpectedly changed, upending even thebest laid plans. For example, MDOT found that a bridge on another segment of I-75—part of the detour route and a criti- cal evacuation route from downtown Detroit—had only been scheduled for resurfacing but actually needed to be completely reconstructed. This required freeway lane closures on a detour route for 3 months. What was planned to be a short-term clo- sure of this bridge ended up being a long-term closure and took a critical link out of the system during summer 2008. In addi- tion, each time a new lane closure was required, it was critical to maintain access for emergency vehicles and key evacuation routes. Although the network simulation model was capable of modeling each of the many possible scenarios, the process was not adapted to the time-consuming coordination require- ments. Operations applications, in contrast to planning appli- cations, have shorter time horizons and require faster turnover and shorter information feedback loops. In order for the model to accommodate changes in the field, a contract amendment for the model would need to be updated, funding would need to be allocated, results would need to be analyzed, and work zone mitigation measures would need to be updated. Addi- tional coordination would be needed with project staff and managers to develop, review, approve, and implement mitiga- tion measures. Large-scale network microsimulation is a new technology, and time and effort will be needed for the business processes to adapt to this new technology. The microsimulation model proved to be effective in mod- eling impacts of major freeway closures and in evaluating a number of work zone traffic control strategies. MDOT was able to quantitatively evaluate the impacts in terms of delay on motorists and commercial vehicles and assign costs to that delay to measure the economic impacts of construction clo- sures and the various work zone traffic control strategies. An evaluation of the Gateway simulation model results showed that the work zone mobility plan for the 90-day period during the complete closure of the I-75/I-96 interchange would save about $1.63 million a day in user costs in just the a.m. and p.m. peak periods alone. This was an extremely conservative esti- mate based on an assumption of $16 per hour in user costs. However, as effective as the microsimulation model was in this project, without a process in place to continually update the model based on actual conditions during construction in the field, the model will likely become out of date on large projects during the construction phase. Concurrent with the modeling effort, three major efforts were developed and implemented. These included incident management under the direction of Metro Region Traffic and Safety and the MITS Center; the addition of real-time sensors and travel advisories brought into operation under the MITS Center; and a public involvement and stakeholder outreach effort involving meetings, presentations, and the generation of feedback from major corporations in the auto, auto supplier, and logistics industries. A comprehensive public involvement

41program was maintained with Detroit’s Mexicantown com- munity as well. Coordination with MDOT’s Detroit Trans- portation Service Center (TSC) was also critical to the work zone mobility effort. The Detroit TSC is responsible for all the other projects on the Detroit network and for responding to events and other contingencies. Background of Agency Four groups within MDOT Metro Region worked together in the work zone modeling for the I-75 Ambassador Bridge Gate- way Project: Planning, Traffic and Safety, Construction, and the Detroit TSC. Once an initial model of the closure was devel- oped, MDOT Metro Region Planning, Traffic and Safety, and Construction worked together to evaluate different construc- tion scenarios and, where possible, adjusted closure schedules or construction staging to minimize the impacts of the project. The MITS Center also participated in planning for the con- struction. Although the MITS Center was not directly involved in work zone mobility modeling and planning, they were inte- gral to the effort through their operation of the real-time and incident management programs. The MITS Center serves as MDOT’s TMC for southeast Michigan and monitors over 200 mi of freeway. The MITS Center manages real-time oper- ations and, under the direction of Traffic and Safety, runs the Incident Management Program. In addition to the permanent traffic detectors, CCTV cameras, and DMS that the MITS Cen- ter regularly operates, numerous portable devices were brought in to assist with monitoring traffic and providing traveler infor- mation throughout the work zone. Process Development The process used for the work zone modeling of the I-75 Ambassador Bridge Gateway Project can be attributed to three factors. First was the great likelihood that shutting down I-75 would adversely affect the mobility of residents in southeast Michigan, manufacturing along the I-75 corridor, and inter- national trade with Canada. It was critical for MDOT to understand the impacts of shutting down I-75 and to deter- mine how to set up traffic control and detour routes in a man- ner that would have the least impact on the transportation network. The second factor that drove the process was the existence of the SEMSIM model that allowed MDOT to build on the existing network model and to develop detailed models of the work zone traffic control strategies. Unlike other planning and design applications, work zone mobility requires a system perspective. Closing a part of an interstate freeway would have systemic impacts on other freeways, system interchanges, and major arterial roads. The SEMSIM model, as enhanced for the Gateway Project, included the core freeway network in theCity of Detroit and the major state trunkline roads, thus pro- viding this capability. Finally, the U.S. Department of Transportation (USDOT) Final Rule on Work Zone Safety and Mobility requires that the impacts of work zones be determined and that transportation management plans be developed to mitigate those impacts. These new rules require that planning for work zone mobility should start as early as possible, even in the project concept stage. These requirements and the technology for large-scale microsimulation were not available until just before construc- tion of the Gateway Project. However, this same SEMSIM/ Gateway model is being repurposed for two other mega proj- ects, which are presently in predesign. Thus, for the first time ever, MDOT will be employing advanced traffic modeling techniques to perform construction staging and work zone mobility planning before design. Microsimulation will allow MDOT to effectively determine the impacts of the work zones and test various strategies to mitigate those impacts in the most effective ways. Detailed Process and Integration Points Figure 4.2 presents an overview of the process that was used to develop the work zone traffic control model for the I-75 Ambassador Bridge Gateway Project. MDOT Metro Region Planning, Construction, and Traffic and Safety reviewed the models that were developed of the alternatives for construction closures for each phase of construction and selected the closure plans based in part on the impact of the closures on motorist delay and mobility. The selected plans were shared with the MITS Center before the start of construction to allow the MITS Center time to develop strategies for the operation of the system, including how to handle incident management and provide real-time information. One of the challenges of the process was that, when conditions changed in the field, there was not a process available that allowed for quick updates to the model. A process that could adjust the model for changes in the field and assist MDOT in selecting new alternatives for construction closures would be valuable and assist MDOT in minimizing delay and maintaining mobility.This process is considerably different from the process used in planning applications. Traditionally, MDOT has used micro- simulation for environmental clearance for large capacity improvement or expansion projects. This process involves a much wider cross-section of the department and is much more integrated into ongoing MDOT business processes. Timelines and information feedback loops are much longer. In addition, these planning applications were focused on individual proj- ects and did not involve modeling the whole network. A CORSIM simulation model of the Gateway Project was origi- nally created in the Environmental Clearance stage of the project, but this was project-specific and did not involve the

42Figure 4.2. Detailed business process diagram of MDOT work zone traffic control modeling.network. The technological innovations of programs such as Paramics and VISSIM opened up new opportunities for net- work traffic analysis. Several key integration points were identified in the MDOT work zone traffic control modeling process, including the following: • Integration between MDOT Metro Region Planning, Con- struction, and Traffic and Safety to model impacts of con- struction, select the best work zone traffic control strategies, and develop operational strategies; • Coordination and integration with the Detroit TSC, which is responsible for other Detroit projects. Some of these were included in the simulation for the Gateway. All required coordination of traffic plans; • Continual integration during construction between MDOT engineers responsible for construction and MDOT plan- ners responsible for modeling to incorporate construction changes into the model and develop new work zone traffic control strategies; and • Use of existing SEMSIM Paramics network model of south- eastern Michigan to repurpose it for microsimulation of freeway closures.Types of Agencies Involved In addition to MDOT Metro Region Planning, Traffic and Safety, Construction, Detroit TSC, and the MITS Center, the process also relied on the work completed by the consulting team selected to do the modeling and the contractor doing the construction. These groups all worked well in the initial plan- ning stages for construction. However, the real challenge was during construction, when changes to the actual construction schedule were occurring daily because of another project in the Gateway Project’s influence area and it was not feasible to update the Paramics model. In reviewing the process, MDOT recognized that it will be important in the future to develop a tool that will allow field engineers and technicians to change the model and to try different work zone traffic control scenar- ios. While the microsimulation model was effective for this high-budget, high-impact project, which also had a long plan- ning horizon, other projects with smaller budgets and shorter planning horizons will require a more flexible approach. Specif- ically, general project scheduling and work zone mobility for the annual program, which has multiple simultaneous proj- ects, will require a more flexible process and technology that will shorten the planning and implementation cycle. Presently, the MDOT Metro Region is looking at developing an in-house

43mesoscopic model that can be used for routine scheduling and staging. Organizational changes also might be considered, such as bringing modeling under the direct control of the users, includ- ing the MDOT Metro Region Traffic and Safety engineers responsible for operational decisions. Types of Nonrecurring Congestion Addressed This process addressed nonrecurring congestion caused by work zones for a major project like that of the 18-month clo- sure of I-75. As noted, for projects of lesser impact, a more flex- ible approach is needed. By using microsimulation to develop detailed models of work zone traffic control, MDOT’s Metro Region was able to objectively evaluate scenarios and work with MDOT Traffic and Safety staff and Construction staff to select strategies that provided the most effective mobility. Performance Measures The primary performance measure that MDOT used was to determine the overall cost to motorists based on total delay of the various scenarios. The cost savings provided an effective way to compare different work zone traffic control strategies against each other, and the potential for monetary savings clearly demonstrated the benefits of careful modeling and selecting the best work zone traffic control strategies. The Gate- way Project did not have many alternatives for detour routes, so the task was to make the only available alternative work. The simulation model helped MDOT devise ways to ensure that traffic would flow on the detour routes. For example, through the simulation model, MDOT found that selective closing of system interchange ramps would allow them to maintain throughput on the main detour route, which was a freeway that ran through the heart of Detroit. In addition, auto and truck delay along a set of 35 specific routes was assessed to identify mobility issues along specific pathways. The focus was on maintaining regional and international truck mobility. Benefits The MDOT work zone traffic control modeling provided sev- eral benefits. It provided MDOT with a quantitative measure of total delay based on a project design, as well as the ability to compare work zone traffic control strategies and determine options with the least delay. By associating cost with delay, MDOT was able to measure the monetary impact of different scenarios. The process also allowed the MITS Center to coor- dinate incident and real-time management along the detour routes, giving them advance notice of closures and projected traffic volumes so that they could develop operational strategies.Lessons Learned The existence of the SEMSIM microsimulation model was crit- ical in allowing MDOT to perform a detailed microsimulation of the entire network around the I-75 Ambassador Bridge Gate- way Project. By repurposing the Paramics’ SEMSIM model, MDOT was able to accurately and cost-effectively develop and evaluate work zone traffic control strategies around the project. The rapidly changing conditions in the field during con- struction led to changes from the initial mitigation plans. Because field engineers and technicians could not access the model used for developing work zone traffic control strategies, there were a few instances when construction plans changed but were not incorporated into the model. Problems arose when other projects whose closures were in the area of influ- ence of the Gateway Project encountered changes. To address this challenge, MDOT Metro Region plans to test a one- county mesoscopic model using DYNASMART for modeling on a future project. Although DYNASMART does not provide as many capabilities as Paramics, it is an easier tool to use and more suitable for in-house use by engineers and technicians that will not have the time to do detailed modeling. The hope is that an engineer or technician in a field office can use DYNASMART to keep up with changing conditions and con- tinue to refer to the model to select the best work zone traffic control strategies. Analysis and Research Observations Use of microsimulation models to evaluate the impact of work zone traffic control strategies proved to be effective for the ini- tial construction. However, this project revealed some weak- nesses in the process. These primarily concerned the lack of flexibility that limited the use of the Gateway Model to respond to unexpected developments. This flexibility relates to both the technology and the process. The modeling work was per- formed by consultants, and the MDOT contracting process in effect on this project did not allow quick enough response to sudden changes. While a large-network microsimulation model is very useful for high-impact projects such as the Gate- way, there is a need for a more flexible tool for other, lower- impact closures, as well as for staging multiple projects on the system. The problem that emerged during the Gateway clo- sures was related to another project that was on the Gateway detour route. The planning horizon and budget for such proj- ects do not permit large-scale microsimulation. An alternative approach might be a network mesoscopic model that can be run in-house and be under the control of the operations engi- neers who are responsible for making decisions. The Ambassador Bridge Gateway Project marks the first time that network microsimulation has been used in an operations application. This provided a valuable learning experience on

44the use not only of microsimulation but also of any advanced traffic modeling in the operations environment. First, it taught that advanced network traffic analysis is direly needed to support high-impact operational decisions on a con- gested urban freeway network. The cost of delay and of travel time unreliability to users, especially commercial users, is esti- mated in the hundreds of millions of dollars. Given that mul- tiple concurrent construction-related closures are an ongoing or annual occurrence, a scientifically sophisticated, systematic approach must be implemented to plan for such disruptions. Second, the interdependent nature of a congested urban free- way network means that an incident or closure at one location will usually have wide-ranging ramifications. Typically, there are dozens of simultaneous projects in each other’s influence areas whose closures need to be coordinated. Presently, net- work simulation is the only tool that can provide the traffic analysis needed to stage, coordinate, and mitigate multiple interacting projects. Third, the business processes in an operations environment are radically different from those in a planning environment:conditions are extremely dynamic, construction schedules and staging schedules change daily, and events and incidents and unforeseen contingencies, like the discovery of a bridge deck in need of emergency replacement, will upend the best laid plans. It can be expected that technology will continue to change. Someday, there may even be real-time simulation. The chal- lenge to DOT business processes will be ongoing. For the pres- ent, however, new, more dynamic processes will be needed if the full potential of the new traffic simulation technology is to be realized. References 1. FHWA, U.S. Department of Transportation. Work Zone Safety and Mobility Rule. http://ops.fhwa.dot.gov/wz/resources/final_rule.htm. Accessed July 19, 2011. 2. Guidelines for Implementation of the Work Zone Safety and Mobility Policy. North Carolina Department of Transportation, 2007. 3. Hardy, M., and K. Wunderlich. Traffic Analysis Toolbox Volume IX: Work Zone Modeling and Simulation—A Guide for Analysts. Report FHWA-HOP-09-001. FHWA, U.S. Department of Transportation, 2009.

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TRB’s second Strategic Highway Research Program (SHRP 2) Report: S2-L01-RR-1: Integrating Business Processes to Improve Travel Time Reliability addresses various ways that transportation agencies can reengineer their day-to-day business practices to help improve traffic operations, address nonrecurring traffic congestion, and improve the reliability of travel times delivered to roadway system users.

The project that produced this report also produced SHRP 2 Report S2-L01-RR-2: Guide to Integrating Business Processes to Improve Travel Time Reliability.

An e-book version of this report is available for purchase at Google, Amazon, and iTunes.

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