Chapter 3. STATE AGENCY SURVEY SUMMARY

Methodology

Responses by State Agency

Arizona Department of Transportation

Arkansas State Highway and Transportation Department

California Department of Transportation

Colorado Department of Transportation

Connecticut Department of Transportation

Illinois Department of Transportation

Indiana Department of Transportation

Iowa Department of Transportation

Kansas Department of Transportation

Kentucky Transportation Cabinet

Louisiana Department of Transportation and Development

Maryland Department of Transportation

Massachusetts Highway Department

Michigan Department of Transportation

Minnesota Department of Transportation

Missouri Department of Transportation

Nebraska Department of Roads

New Hampshire Department of Transportation

New Jersey Department of Transportation

New York State Department of Transportation

North Carolina Department of Transportation

Ohio Department of Transportation

Oklahoma Department of Transportation

Oregon Department of Transportation

Pennsylvania Department of Transportation

South Dakota Department of Transportation

Tennessee Department of Transportation

Texas Department of Transportation

Virginia Department of Transportation

Wisconsin Department of Transportation

Chapter 4. STATE CASE STUDIES

Ohio Department of Transportation (ODOT)

PDP for Major Projects—Steps 1 & 2

PDP for Major Projects—Steps 3 & 4

PDP for Major Projects—Step 5

PDP for Major Projects—Step 6

PDP for Major Projects—Step 7

PDP for Major Projects—Steps 8 through 12 (Detailed Design)

PDP for Major Projects—Step 14 (Construction)

PDP for Major Projects—Post Construction Activities

Virginia Department of Transportation (VDOT)

TTC Planning

Work Zone Monitoring, Review, & Evaluation (60)

Night Work

Use of Virginia State Police (VASP) In Work Zones

Public Information & Outreach Strategies

Oregon Department of Transportation (ODOT)

Statewide Work Zone Planning

Project Level Work Zone Planning

ODOT’s Work Zone Traffic Analysis (WZTA)

ODOT’s “QuickFax” Service (71)

Chapter 5. Conclusions

Comprehensive Consideration of Work Zone Impacts throughout the Project Development Process

Policy and Policy Plan Level Direction on Work Zone Impacts

Performance measurement, data collection and data standards

References

LIST OF FIGURES

Figure 2.1. Mn/DOT project development stages

Figure 2.2. Example of deterministic queuing theory

Figure 2.3. Volume and speed distribution before, during, and after a work zone queuing event

Figure 3.1. Surveyed states

Figure 3.2. Generic project development process

Figure 4.1. ODOT’s Red Flag Summary for maintenance of traffic (50)

Figure 4.2. ODOT’s MOT policy process (52)

Figure 4.3. ODOT’s permitted lane closure capacity calculation process (53)

Figure 4.4. Example of ODOT’s permitted lane closure web site (52)

Figure 4.5. Work zone contra-flow concept utilized by ODOT (55)

Figure 4.6. ODOT’s real-time work zone crash database main screen (57)

Figure 4.7. ODOT’s work zone crash report data entry form (57)

Figure 4.8. ODOT’s work zone crash frequency comparison chart (57)

Figure 4.9. VDOT’s project development process (PDP) (59)

Figure 4.10. VDOT’s work zone safety checklist form (61)

Figure 4.11. VDOT’s work zone review team interview form (62)

Figure 4.12. ODOT’s PDP highlighting traffic control planning (68)

Figure 4.13. ODOT’s traffic control supervisor’s work zone safety checklist (69)

Figure 4.14. ODOT’s standard work zone capacities (68)

Figure 4.15. ODOT’s traffic volume matrix (68)

Figure 4.16. ODOT’s work zone traffic analysis (volume vs. capacity) (68)

Figure 5.1. Average speeds at the second device

LIST OF TABLES

Table 2.1. Data elements for consideration during preliminary engineering for TMP refinement

Table 2.2. Caltrans TMP strategies and their elements

Table 2.3. Performance measures for the evaluation of work zone traffic management technology

Table 2.4. Highest free-flow measurement before queuing initiated

Table 2.5. Variables known to impact work zone capacity

Table 4.1. Project classifications and corresponding processes (49)

Table 4.2. ODOT’s MOTAA potential constraints checklist (51)

Acknowledgments

The researcher would like to thank all the individuals who participated in our interviews. The names of the interviewees are listed in Chapter 3 and are associated with the individual states they represent. The authors are especially thankful for the guidance provided by Tom Notbohm, advisory committee chair, of the Wisconsin Department of Transportation. Other advisory committee members included Jim Brachtel, Iowa Division Office of Federal Highway Administration; Robert Alva, Kansas Division Office of Federal Highway Administration; Wallace Heyen, Nebraska Department of Roads; Kurt Miyamoto, Kansas Department of Transportation; Tracy Scriba, Office of Operations, Federal Highway Administration; and Daniel Sprengeler and Mark Bortle, Iowa Department of Transportation.

Chapter 1. Introduction

Federal Highway Administration (FHWA) has published Administrative Final Rule CFR part 630 Subpart J, “Work Zone Safety and Mobility,” on September 9, 2004. In general, the rule requires that state transportation agencies (STAs) develop policies to investigate the safety and mobility impacts as early as possible in the project development process: quantify the impacts, look for alternative actions which will reduce the impacts, select a work zone approach and communicate the impacts of the approach to the public, measure the safety and mobility performance of the actual work zone once it is put in place, and use the performance data of past programs to manage the impacts of future work zone activity. The rule provides some flexibility by allowing each state to set its own procedures and policies to comply with the rule and by allowing states to seek solutions which are commensurate with the severity of the potential impacts and require the most aggressive planning for “Significant Projects.”

The above paragraph greatly simplifies the specific processes outlined in the proposed rule. The reader wishing more information should read the rule and attend information workshops held by FHWA staff members, as well as read a soon-to-be-released implementation guide on the new rule (see FHWA Office of Operations Web site) (1). The purpose of this document is to provide a synthesis of what is currently being done by STAs across the country to plan, manage, operate, and evaluate work zone safety and mobility. This is by no means a comprehensive review of what is being done by STAs, nor does it provide enough detail to fully document the activities of any state. The purpose of the research described in this report is to provide a snapshot of what is taking place at STAs throughout the country so that professional staff at STAs attempting to meet the letter and spirit of the new Work Zone Safety and Mobility rule will have a conceptual view of what other STAs have and are using to plan, manage, operate, and evaluate work zone safety and mobility. Throughout the document, we attempted to document the individuals we spoke with at STAs.

Research Steps

The research to develop this synthesis was broken into three distinct steps. The first step was to review the literature regarding work zone safety and mobility strategies. The second was to conduct interviews with staff members at 30 STAs. The interviews were conducted over the telephone using an outline, but each interview was tailored to the responses and the domain of knowledge of the interviewee. The last step was to conduct more detailed case studies of three STAs. The case study states were selected by the advisory committee. There is some interaction between the three steps. For example, some of the issues discovered in the interviews lead to inclusion of that information in the literature review.

In all parts of this report, we attempted to follow the work zone elements in each step of the project development process, starting with activities well in advance of the project construction. For example, some agencies include consideration of work zone impacts in policy document (long-range plans and agency policy) long before the projects are detailed at even the conceptual level. We attempted to document followed strategies ranging from the policy level, conceptual level, and project planning and environmental documentation level, through design, during work zone operation and work zone evaluation and monitoring, and through post project evaluation (postmortem).

Findings

All representatives of STAs had one or more strategy that their agencies had developed or were developing, and they spoke enthusiastically about progress they were making. Almost all individuals understood that the new work zone rule would encourage their agencies to think more comprehensively about work zone safety and mobility. A couple of agencies felt that they were very close or already met the spirit of the new rule.

In general, there were some weaknesses that were pretty consistently observed in most (not all) STAs:

1. A lack of agency policy level direction on work zone safety and mobility.
2. A lack of processes that identify the evaluations of work zone safety and mobility impacts throughout the project development and processes to understand how various offices (functional areas of expertise) should interact throughout the life-cycle of project development to plan, manage, operate, and evaluate work zone strategies.
3. A lack of common, consistent, and continuously applied performance data collection processes to allow the comparison of work zone safety and mobility at locations, between locations, and even between STAs.

Organization of the report

The first chapter is introduction. The next three chapters are stand-alone documents. Chapter 2 presents the literature review. Chapter 3 presents the results of interviews with representatives of 30 STAs. There are no comparisons made between states. Each interview attempts to document strategies that each STA uses to manage work zone safety and mobility. Chapter 4 documents the programs of three STAs—Ohio, Virginia, and Oregon. This chapter is intended to provide more specific details on strategies these STAs are using. The last chapter, Chapter 5, closes the report with conclusions and recommendations.

Chapter 2. Literature Review

Although the objective of the project is to look at safety and mobility strategies to improve the traffic operation of work zones, safety and mobility are often two sides of the same coin. That is, when congestion is reduced and traffic operations are more efficient, work zones are safer, and when work zones are safer, traffic operations are more efficient. However, policy initiatives and activities to improve work zones are generally motivated by mobility or safety, and while the implementers of the strategies may recognize the synergy between safety and mobility, the strategies are generally driven by one or the other concern. In this literature review, we will review safety and mobility strategies together and move through the work zone life-cycle, starting with project conceptualization and moving through the project life-cycle to the conduct of a postmortem following the completion of the work zone.

This review only investigates the literature at a very high level. National reviews of best practices and national self-assessments have been conducted to identify practices that are being applied by individual state transportation agencies (STA) with varying degrees of success (2,3,4). Much of the information presented here is derived from our survey of practices that states (individual results from specific STAs are summarized in Chapter 3) have applied throughout a project life cycle to better manage congestion and safety issues within work zones.

The outline for reviewing safety and mobility strategies follows a construction (or reconstruction) project development process, starting from the activities conducted earliest in the project development stages and working its way through the project delivery process to the actual construction and post-construction evaluations. Work zones for maintenance activities can have impacts on traffic operations similar to reconstruction projects, but are generally much shorter in duration and may be reviewed by an agency using some of the same processes it uses to assess the impacts of highway reconstruction projects. The Ohio Department of Transportation has developed a very nice model for defining a project’s degree of complexity and the need for more or less preparatory effort for the work zone. This model is discussed in the Ohio case study in Chapter 4 of this report.

As highway reconstruction projects are developed, they conventionally go through several steps. Project development starts with long-range planning and other policy plans in which projects are dealt with at an abstract policy level. Next, in project programming, steps are taken to provide more definition to the project, starting with scoping and environmental documentation. Project programming may then move the project into preliminary engineering and then to final (detailed) design, where the plans and specifications are prepared to allow the STA highway reconstruction. During construction, there are operational and work zone quality control activities to manage. Following construction projects, there are opportunities to assess the project and look for lessons for continuous improvement. Although the steps sound straightforward and sequential, in reality the lines between each step can be blurred. For example, project programming includes programming for the construction itself, but pre-construction activities are also programmed, including project scoping, environmental documentation, and design. At each step in the project development process, decisions can be made regarding work zone safety and mobility. Therefore, the simple set of steps in the development process is used to discuss types of mobility strategies. We have chosen to break project delivery into seven simple steps. In Chapter 4 we describe the Ohio DOT’s process, and they have broken the project delivery process into 14 steps (all 14 steps are discussed in Chapter 4). The more coarse aggregation of steps used here provides enough detail for this discussion. The steps we use for illustration are as follows:

• Long-range network planning, policy planning, and network scoping
• Project programming and project planning
• Preliminary design
• Final design
• Contracting
• Project work zone administration and traffic operation
• Post-project evaluation (postmortem)

Following the discussion of actions taken at each of these seven steps of project development, we provide a brief discussion of the computer tools used to quantify and estimate work zone traffic operational impacts. Because the most important variable in determining queuing and delays at work zone is the estimate of the capacity of the work zone following a lane closure, the text discusses attributes of the work zone, the traffic, and the environment that can adversely impact capacity at work zone lane restrictions.

Long-Range and Policy Plans

Generally, long-range plans very broadly address specific improvements, and if they address projects at all, they lack definition. Therefore, it is difficult to address specific work zone mobility strategies and safety strategies, but it is possible to set policy for how projects will be designed, managed, and contracted. For example, some states may encourage the use of strategies to combine adjacent projects within an urban area, reduce the duration of projects, or encourage the use of innovative contracting strategies (contractor incentives and disincentives) to reduce the duration of projects or discourage simultaneous work on parallel corridors.

Some STAs have adopted policies or policy plans regarding work zone mobility. For example, some STAs have set policies on maximum queue length or maximum delays imposed on motorists due to work zones, or have even created prohibitions on daytime closures in urban freeways. For some states, these policies are imputed into lane closure policies that are based on hourly or daily traffic volume and define where and when the agency is precluded from closing one or more lanes. For example, the Minnesota Department of Transportation (Mn/DOT) publishes a manual that specifies when (during what hours of the day and days of the week) and where a lane can be closed (5). Implicit in this manual is a policy regarding the maximum amount of delay the agency can impose on road users when a lane is closed. Although it is a static manual, it is based on published highway capacities and historical traffic volumes and traffic patterns.

One of the issues associated with blanket lane closure policies is that the policy may not be founded on traffic demand and operational characteristics of the specific situation, and when broadly applied (in a one-size-fits-all policy), it may not result in a cost-minimizing solution. An example in which economics is used to drive lane closure decisions, as opposed to delay estimates or queue length thresholds, is the system implemented by the Oregon Department of Transportation (ODOT) (6). ODOT was the first agency to use the national Highway Economic Requirement System (HERS) model and apply it at the state level. The Oregon has become the first state-level user of HERS and the national model evolved into the HERS-ST (state version) software package. This model is an economic model that estimates the user costs (safety and mobility), some environmental costs, and the agency costs for the highway system (e.g., improvements and system preservation). Using HERS-OR, ODOT developed a spreadsheet model to estimate the user costs for delays resulting from lane closures at various locations throughout their highway network. These costs are then used to evaluate the impact of lane closures, including work zone lane closures at a conceptual level of planning.

In many cases (such as the Mn/DOT example), the agency may not recognize practices that limit the maximum delay or maximum queue length as a policy-level decisions, but these limits informally become agency policy.  In a few cases delay or queue length threshold at work zone lane closures were established through policy making. One state told us that maximum work zone delays were set by the state’s governor following the governor’s experiencing an excessive delay due to a work zone while traveling to an appointment.

As noted in the 2002–2003 FHWA work zone self-assessment, most agencies have not established goals for reducing crashes and delays in work zones (1). However, some agencies established such goals. For example, ODOT has stated that its goal is to “[m]aintain the number of fatalities in work zones per year at or below ten through the year 2010” (7).

Project Programming and Project Planning

The planning and programming processes tends to vary from STA to STA, but most construction or reconstruction projects begin with the identification of a system deficiency. When the system deficiency becomes a high priority, a conceptual-level plan is developed and project development activities are programmed into the Transportation Improvement Program (TIP) plan. At this point in the pre-construction process, decisions are beginning to be made about project scheduling, contracting method (design-bid-build, design-build, or another project delivery method), the consolidation of multiple projects into a single large project, and project costs and financing. Figure 2.1 is a graphic taken from the Mn/DOT Highway Project Development Process Handbook that shows the steps for taking a project from concept to construction to highway operation (8). Although the project development process can be drawn as a series of steps, for complex projects, the process is more likely to be interactive. For example, a project might be scheduled to be conducted as a design-bid-build project at the conceptual stage, but later, during preliminary engineering when a scheduling and phasing plan is developed, it is discovered that the standard delivery processes will needlessly delay the project. To expedite project delivery, the STA can decide to deliver the project using design-build, thus combining two steps and reducing the number of contracts with consultants and contractors.

Figure 2.1. Mn/DOT project development stages

Clearly, the scale and location of a project will impact how early in the project development process the work zone impacts should be considered. For example, the reconstruction of a critical and major river crossing within a large urban area may be a good candidate for very early consideration of work zone impacts. Depending on local conditions, partial or complete closure of the bridge may trigger the use of a network model to understand the traffic impacts of the closure. On the other hand, the work zone impacts of converting a rural two-lane highway to a four-lane rural divided highway may not require early consideration. Considerations for the work zone management for routine and less complex projects may be appropriately considered much later, in the project’s final design.

Following conceptual plans, the next step in the project programming process is typically to conduct a detailed scoping study, at which point the project starts to move through the pre-construction project development process. In scoping, the limits of the project are determined and the fundamental functionality of the project is identified. The scoping document will identify the project components, identify project alternatives for evaluation, and provide a plan for agency and public involvement. From this point forward, until construction starts, planning and design decisions are made that impact work zone management during construction. The project scope will generally result in entering the project into the TIP. For high-impact projects, the California Department of Transportation (Caltrans) requires that a Transportation Management Plan (TMP) should be started during scoping. The traffic management and traffic mitigation costs from high-impact projects are likely to be significant, and these costs should be included as preliminary budgets are being developed (9). Although it is not clear that other agencies develop TMPs this early in the project development process, the FHWA’s work zone self-evaluation found that 57% of the STAs reported that their TIP was managed to avoid congestion due to poor scheduling of projects (3).

Naturally, when TMPs start very early in the process, the ultimate plan must evolve as the project’s scope becomes more defined. However, it is important for projects with significant traffic impacts that planning begins early to allow enough time to execute the strategies in advance of the initiation of construction. For example, if car pooling were employed as a mitigation strategy, this might involve an entire project development process for the construction of park-and-ride lots, which may require years to execute.

The Work Zone Safety and Mobility Federal Administrative Rule Schedule uses language similar to that of Caltrans’ guidance. The federal administrative rules specify that interstate system projects in transportation management areas (urban areas with a population of more than 200,000) with significant impacts must have a TMP. Similar to Caltrans’ guidance, the federal administrative rules encourage STAs to begin developing TMPs early in the project development process. The administrative rules state that the “TMP consists of strategies to manage the work zone impacts of the project.”

Understanding the impacts of a major project in an urban area is complex. Trips will be diverted from the impacted route to parallel routes, or travelers will look for alternative modes of travel. Some travelers may even find alternatives and may not make the trip at all. The conventional wisdom is that when the capacity of a specific roadway has been reduced, the number of travelers diverted to other routes and modes in the corridor will be approximately equal to the peak-period reduction in capacity required by the reconstruction project (10). Assuming that this is the case, then, understanding the paths and modes for diverted trips requires an analysis that uses a network model with trip distribution and perhaps modal split estimation capabilities.

More detailed study of traffic diversions during closures has shown that conventional thinking about trips in response to road closures or capacity decreases overestimates the trips that will reappear somewhere else in the network when capacity is decreased (i.e., during lane closures due to construction). In other words, when lanes are closed due to construction, the conventional assumption that trip makers will continue making the same trip following the same path or a parallel path may result in overestimated impacts. To further understand traveler behavior when facilities are closed, impact studies have been conducted for transportation system disruptions resulting from constructions projects, natural disasters, and other events that cause the total closure of a roadway. There are many such studies of landslides that have closed roads in New Zealand, earthquakes that have collapsed freeways in California, and transit strikes in large urban core areas (11). However, the most comprehensive, controversial, and widely cited study is one by Cairns, Hass-Klau, and Goodwin conducted for London Transport and the Department of Environment (12). The main questions this study set out to answer were (1) “what really happens to traffic conditions when road capacity is reduced or relocated?” and (2) “what are the underlying changes in travel choices and behavior that cause these effects?”

The authors collected over 150 sources of information regarding 100 locations and included over 60 case studies. Capacity reductions examined included road maintenance activities, bridge collapses, natural disasters, labor strikes, etc. In their case studies, the authors found that the unweighted average number of trips was reduced in the treated area or in the area by 41%. On average, less than half of this traffic then reappears on alternative roads at the same or different times of day. This suggests that quite a few trips simply dissipate naturally.

The authors examined different kinds of conditions during which roads are reduced in capacity or roads are closed. The authors determined that the response (reduction in traffic) is a result of the number of alternative routes, the duration of the capacity reduction, and the alternative modes of travel. However, in studying even short-term closures due to railroad worker strikes, the authors found that users seemed to be able to accommodate capacity reduction very quickly. This is in part due to information available regarding the capacity reduction that allows the public to adjust their trip-making behavior. The authors found that in some cases, even on the first day of the disruption, there was no substantial “traffic chaos,” and the lack of chaos is often greeted with the bemusement of the press and transportation professionals. They also found that the extent of publicity and information before the change might itself influence expectations and outcomes.

From the work by Cairns, Hass-Klau, and Goodwin, we can see that travelers are amazingly resilient in working their way through a closure or a capacity reduction. However, much more research needs to be done to understand how travelers tend to accommodate construction road closures or partial closures. However, it is expected that the response is likely to be related to several variables, including the information available to the traveler about the work zone, traffic conditions at and around the work zone, the types of trips (recreational or work), alternatives and knowledge of alternatives, and the duration of the lane occupancy by a work zone. However, the good news that Cairns, Hass-Klau, and Goodwin discovered is that, given enough information, travelers will adjust and are amazingly resilient and resourceful when faced with a capacity reduction.

Saag, while conducting a synthesis of methodologies for reconstructing urban access-controlled facilities, found evidence that tends to conform to the findings of Cairns, Hass-Klau, and Goodwin (13). Saag found that “[e]ven when lane closures during construction are required, experience has shown that many predictions of dire adverse traffic conditions resulting from the closures did not materialize.” Saag also emphasizes the need for public information and communication. Saag recommends that the need to involve the public transcends all study phases, from early planning through construction.

An environmental study and documentation follow project scoping. To determine project limits and impacts, a preliminary geometric layout must be completed during environmental documentation. For projects with high impacts, environmental documentation involves planning for the work zone through involving the public, assessing the impacts of alternatives, and identifying strategies to mitigate adverse impacts. Alternatives considered during environmental documentation should be evaluated for their impacts both during and after construction.

The environmental document results in a preliminary geometric layout that can be used for a more specific assessment of the traffic impacts resulting from a high-impact construction project. At this stage, the TMP can be further refined. For major projects, the planning and design management approach for traffic is a comprehensive effort to accommodate traffic during construction. The TMP should assess the impact to the region and determine potential solutions (e.g., demand management strategies, improvement of parallel routes, etc.) rather than offer localized remedies to specific issues within the project limits (e.g., individual traffic control devices). This information can be used to begin developing the traffic operation (TO) plan and to begin delivering the public involvement (PI) portions of the TMP. For example, at this stage the Ohio Department of Transportation conducts an analysis of the preferred alternative resulting from the environmental document to determine whether lane closures are feasible (given the department’s maximum queue length policy) and, if lane closures are possible, the times of the day or days of the week during which lanes closures would be feasible (limited by their lane closure policy on maximum delay). Information on permitted lane closures helps drive further TMP planning as the TMP evolves.

Preliminary Design

Preliminary design should define the layout and types of facilities (e.g., interchange types); identify the roadway cross-section, profile, and alignment; and identify all right-of-way requirements and all roadway operational issues and traffic control. At this point, the TMP should begin to form. Designers can begin to look at the delay associated with alternative phasing and construction scheduling scenarios, alternative closures and detours, the impact throughout the network due to different lane closures and restrictions, and even full closures. Since traffic operation in the work zone will dictate the details of the temporary traffic control (TTC) plan, the development of a TTC for significant projects should take place at this stage.

Since traffic control plans have long been a requirement of federal aid projects, and since most states require traffic control plans for all projects, regardless of whether federal aid is involved, TTCs are a routine aspect of project development (14,15). What differs is the consideration given to TTCs so early in the project development process by the TMP.

During the preliminary staging in project development, a few STAs were found to have developed lists of data elements to check and consider when further evolving a TMP. (Ohio calls these red flags.) Table 2.1 lists elements that Caltrans identifies in its “Transportation Management Plan Guidelines” for consideration once geometric information is available (8).[1] Some of the items listed have to be determined through analysis (e.g., expected vehicle delay) and others are subjective (e.g., political or environmental sensitivity). Clearly, each individual STA might have more or fewer data elements that the TMP developer should take into account or elements that are unique to the agency. Caltrans further suggests that these data elements be taken forward to consider a fairly exhaustive array of potential strategies, as listed in Table 2.2.

Clearly, each strategy must be evaluated for cost effectiveness and the benefits and costs of applying the strategy. However, many of the strategies are known to work well and benefits far exceed the costs (such as media releases), and thus there is no need for an evaluation. However, others will depend on conditions, traffic demand, parallel routes, and alternative modes available. These impacts may also ripple through the network in the surrounding region for major projects in congested urban/suburban areas. In these cases, analysis tools such as work zone traffic operation models, simulations, multimodal demand models, or economic models (e.g., HERS-ST) should be used to select a set of effective strategies and design their characteristics (e.g., schedule for off-peak lane closures).

Table 2.1. Data elements for consideration during preliminary engineering for TMP refinement

Following good planning principles, each strategy should be linked to measures of performance to determine how effective the applied strategy was in reducing the safety and mobility impact of the work zone. Performance measures are typically applied to fulfill four functions (16):

1. To continuously improve services, in other words, to understand how the strategy is performing and whether adjustments of its application are necessary to improve performance
2. To strengthen accountability of either the STA’s or the contractor’s forces to ensure the strategy is achieving the desired effect
3. To communicate the results of strategies to the public and STA managers, which can be critical when decision-makers are asked to make difficult decisions and the public is asked to accept them, such as with full closures; they need to know how these high-cost short-term strategies achieve long-term gains
4. To provide better information for effective decision-making in the future, including resource allocation; in other words, to gain a knowledge base of the applicability and benefits of the strategy

Performance measures for work zones are currently far from standard and differ from one agency to the next, and the appropriate performance measures will often vary from project to project. For example, when a TMP calls for mitigation strategies, such as increased opportunities and support services for car pooling, the performance measures should include a measure of increase in car pooling use. Another project in which car pooling was not selected as a mitigation strategy clearly would not use increased car pooling as a performance measure. Further, a work zone may involve a new strategy in which a specific technology is being deployed. In these cases, a unique performance measure may be employed for evaluation purposes.

Table 2.2. Caltrans TMP strategies and their elements

Clear measures of work zone performance are implied by the Work Zone Safety and Mobility Self-Assessment guide (1). These are measurements of mobility that include measures of throughput, such as flows measured in passenger car equivalents, queue length, queue length distribution, maximum queue length measurements, delay while traveling through the queue and the work zone, and travel time through the queue and work zone. Measures of safety include common measures, such as crash rate, crash frequency, crash severity, incident frequency, and time before clearance of incidents. As seen in the Ohio DOT case study, a comparison can be made between the crash frequency in the work zone segment and the crash frequency before the work zone was put in place. When the crash frequency exceeds the crash frequency before the work zone was implemented, a special safety study of the work zone is triggered. Regardless, as we found in our survey of STAs, very few STAs routinely collect and compile performance measurements. More often than not, performance measures are collected on an exception basis. For example, if an agency receives complaints about a specific work zone, this may trigger the measurement of backups.

Table 2.3 lists performance measures and the agencies that use these performance measures (17). These measures were created to measure the impact of specific technology being applied in the work zone. For example, a common application being used in several of the states was the use of speed monitoring devices with a changeable message sign (CMS) to tell the motorist their speed relative to the work zone speed limit and several independent evaluations of this technology have been conducted (18,19,20).

Table 2.3. Performance measures for the evaluation of work zone traffic management technology

Clearly, if there are going to be comparisons of work zone performance within a state and between states, common performance measures and standards for data collection and data processing need to be developed. However, regardless of the measures, the TMP must include resources for data collection, data storage, and data interpretation and analysis.

Caltrans guidelines also recommend that a contingency plan be part of the TMP. The contingency plan identifies what to do and what step to take if congestion and queues exceed what is anticipated and delays become unacceptable. Although Caltrans guidelines only address mobility issues for triggering contingency plans, it would also be prudent to have triggering criteria for a safety contingency plan. For example, Ohio has performance measures that trigger steps to investigate the work zone for safety issues, similar to congestion contingency triggering measures (see Ohio DOT case study). Caltrans contingency plans contain the following elements:

• Information that clearly defines trigger points that require lane closure termination (i.e., inclement weather, length of traffic queue exceeds threshold)
• Decision tree with clearly defined lines of communication and authority
• Specific duties of all participants during lane closure operations, such as a coordinator for state or local police, etc.
• Names, phone numbers, and pager numbers for the district traffic managers or the designee, the resident engineer, the maintenance superintendent, the permit inspector, the on-site traffic advisor, the state police division or area commander, appropriate local agency representatives, and other applicable personnel
• Coordination strategy (and special agreements if applicable) between the district traffic manager, resident engineer, on-site traffic advisor, maintenance, state police, and local agencies
• Standby equipment, state personnel, and availability of local agency personnel for callout (normally requires a cooperative agreement)
• Development of contingencies based on maintaining a minimum service level

Final Design

At the final design stage of the project development process, the details of the project are sufficient to allow an experienced contractor to construct the project. The products of final design are the plans, specifications, and the project cost estimate (PS&E). The PS&E includes the TTC plan for the contractor to execute. At the final design phase, the TMP should only need minor modifications, and for major projects, many of the activities listed in the TMP should already be underway before completion of the final design.

In many respects, the routine TTC plan process that STAs have always used to develop traffic control plans may be applied only after the plans have been made more complex by including more extensive rules and procedures governing mitigation plans, work schedules, performance monitoring, night-work requirements, and the use of intelligent transportation systems (ITS) in the work zone.

Contracting and Project Operations

While the work zone is operating, three aspects of monitoring the operations need to be taken into account:

1. Appropriate application of the TTC plan, drivers’ ability to understand and follow temporary traffic control devices, the condition of traffic control devices, and modification to TTC to improve traffic operations and safety
2. Monitoring of mobility (delays and travel time) in the work zone and adjusting the work zone to meet mobility standards
3. Monitoring safety (conflicts, incidents, and crashes) in the work zone and then making corrections to improve safety in the work zone

The first aspect, reviewing the temporary traffic control, is uniformly conducted to some extent by every surveyed STA. Most agencies have standard procedures for checking the traffic control against the plans and having qualified individuals inspect the work zone while in service to make sure that the TTC devices meet standards, are set-up appropriately, and are conveying clear guidance to drivers. The FHWA has even developed a checklist for inspecting TTC in work zones (21). Some agencies go to the effort of placing a TTC specialist in major work zones to make adjustments to the traffic control on the fly.

Work Zone Postmortem

Most interviewed STAs did not conduct a formal postmortem review of specific projects or of the performance of all projects during a single year. Instead, exchange of information on the performance of work zones was largely done informally. For example, the Illinois DOT schedules quarterly meetings of traffic control supervisors to exchange experience and identify best practices. A few states indicated that they had formal end-of-the-year processes. For example, Colorado has a process in which each project’s resident engineer and regional safety engineer rates each project on a score of 1 to 4 following a specific scoring criteria. All scores and safety statistics are then compiled into an end-of-the-year report. For example, Kentucky has a team that evaluates at least 25 work zones annually, and their findings become part of an annual construction evaluation; Minnesota prepares an annual work zone safety analysis, which also contains safety statistics from the last 11 years to report on safety trends; and during the peak of the construction season, Oregon sends 6 to 12 engineers out to tour as many work zones as they can in two weeks to identify deficiencies, and the results are prepared in an annual report.

The relative dearth of objective data after the project evaluations (postmortem) is largely due to the lack of performance data collected during the actual project. If data are uniformly and consistently collected for all work zones, then the agency can easily develop an annual report that evaluates the status of work zone performance and illustrates improvements in performance from year to year.

Work Zone Planning and Management in the Project Development Process

In this section of the literature review, the steps taken to plan and implement safety and mobility mitigation strategies are identified. This is not intended to provide the detail to allow an STA to adopt and apply a strategy, but rather it is intended to provide examples of what can be done at each project development step and spark the development of work zone safety and mobility strategies to satisfy an agency’s unique circumstances.

Several agencies apply good work zone management principles in several of the steps of project development, with the exception of measuring work zone performance. We found practically no examples of good performance measurement of work zone safety and mobility. Much work remains to be done in this area to create performance measures and to encourage the need to review the performance of work zones.

In the next section, we briefly review analytical tools used to analyze work zone traffic operations and traffic impacts of work zone lane restrictions.

Measuring the Traffic Impacts of Work Zone Lane Closures

Simulation modeling methodologies used to measure the impacts of work zone can be categorized by three dimensions. The first dimension is the queuing model used; most simple procedures use deterministic queuing models. The second dimension is whether the model treats vehicles as individual entities, sometimes called microscopic simulation models, or traffic is treated as continuous flow, known as macroscopic models. Lastly, some models have network capabilities in which vehicles can flow through the model following multiple paths. The most sophisticated network models used to examine work zones have the capability to distribute trips along paths within the network based on internal algorithms, while more simplistic models require that the modeler distributes trips by hand. Each dimension is explained below.

Deterministic Queuing

Three macroscopic methods apply to modeling queues. These are steady state queuing models, a shock wave queuing model, and a deterministic queuing model. In this section, we will discuss only the deterministic queuing model. A reader looking for a comparison of all three should see references (22,23).

Because of its simplicity and elegance, deterministic queuing is most commonly used for model work zone queuing. A deterministic model of queuing is used by the Highway Capacity Manual to determine delay due to lane closures. Memmott and Dudek applied deterministic queuing to work zones in 1982, and this method is incorporated into the computer model QUEWZ, which is used by several state transportation agencies to determine expected delays at work zone lane closures, queue lengths, and user costs (24).

The underlying assumption of this model is that when the number of vehicles arriving exceeds the capacity, the difference between the arrival rate and the capacity is the number of vehicles stored in the queue. An example of deterministic queuing is shown in Figure 2.2. Figure 2.2 assumes that the bottleneck has a capacity of 1,400 vehicles per hour. Starting at time zero there is no queue, but a queue begins to build because the arrival rate (2,000 vehicles per hour [vph]) exceeds the discharge rate (1,400 vph), and at the end of one hour there are 600 vehicles queued upstream of the bottleneck. Figure 2.2 then shows the arrival rate dropping to 800 vehicles per hour after one hour at point B. The discharge rate now exceeds the arrival rate and the queue begins to dissipate. At the end of two hours, the queue has subsided. The number of vehicle-hours of delay the bottleneck imposes is the area of the triangle formed by points A, B, and C. Knowing the number of vehicles in the queue, the length of the queue can be determined by Equation 1.

                                                                                                                                 (1)

where

           

              The number of queued vehicles at time

             

              = The number of lanes upstream from the lane closure

Figure 2.2. Example of deterministic queuing theory

Dixon, Hummer, and Rouphail point out that the difficulty with the deterministic approach is that it estimates the queue at a single point (25). In other words, the model treats the vehicles stored in the queue as if they were stacked vertically rather than distributed across a length of road upstream from the lane closure. Therefore, the behavior of the queued traffic upstream of the lane closure is not influenced by the lane closure.

Highway Capacity Manual methods and QUEWZ and its derivative models, including QUEWZ3, QUEWZ-85, QUEWZ-92, and QuickZone, all use a deterministic queuing model to estimate queue length and delay. Other agency-specific models have been built based on a similar methodology with inputs and outputs customized for the agency. For example, the Ohio DOT uses an agency-developed spreadsheet-based model for estimating work zone impacts (26). All versions of QUEWZ assume a closed network, meaning that all vehicles entering the simulation can only be discharged by going through the deterministic queuing model. QuickZone is a more sophisticated model that allows the user to create a network, but the principle model used to estimate delays and queue length is the deterministic queuing model. However, because QuickZone is a network model, it can estimate delay for an entire corridor, and the model can run network-level scenarios where traffic is diverted to parallel routes (detours). The user specifies the propensity for drivers to divert to a detour. Since manual input is required to estimate the network impacts of a lane restriction (a lane closure), the size of the network and the estimation of the impacts within the network may be limited to the mainline where work is being constructed and a few parallel diversion routes. This makes QuickZone applicable to many urban applications and almost all rural applications, but not to major closures in dense networks. For example, in the Minneapolis/St. Paul metropolitan area, the Mississippi River bisects both core cities. During 2004, Mn/DOT had construction and/or maintenance work scheduled for the bridges on all three of the interstate and interstate-like roadways crossing the river on the St. Paul side of the metropolitan area. The result was simultaneous lane closures for a few weeks on all three structures. Lengthy backups were experienced. Estimating the significant and complex network effects in the Minneapolis/St. Paul metropolitan highway system is significantly beyond the capabilities of QuickZone.

The ability of models based on deterministic queuing models to forecast queues, queue length, and delays accurately depends on the capacity estimate at the lane restriction, and therefore a good estimate of capacity is the most critical input. Although different programs may make different assumptions regarding the density of vehicles (vehicles per mile) in the queue to determine the queue length, all should calculate the same number of vehicles in the queue given the same capacity during a work zone-related lane restriction. Therefore, estimating the capacity of the roadway within the work zone becomes critical, and several recent studies have investigated the capacity of freeways with lane closures (27,28,29).

Dixon and Hummer found that in most cases the capacity of work zones is governed by the efficiency of drivers to converge into the through lanes at the merge point. Traffic control and enforcement activity that cause vehicles to merge into the through lanes upstream from the lane closure taper (early merge schemes) make the capacity of the work zone dependent on the efficiency of the merge upstream (where there is space to merge at high speeds). Traffic control and enforcement that results in vehicles merging at the lane closure taper (late merge schemes) result in the capacity being governed by the merge near the taper (where there are space limitations that require that merging occurs at low speeds). Dixon and Hummer also found that in some work zones in which construction work is taking place very close to the open lane, the proximity of the construction work to the open lane may govern the capacity of the work zone.

Table 2.4 shows traffic volume measurements taken immediately prior to the initiation of a queue at a work zone on I-80 near Davenport, Iowa, during the summer of 1998. The volumes shown in the middle columns of Table 2.4 are the raw volume counts; the highest volume recorded just prior to queuing varies from about 1,300 vehicles per hour to almost 1,600 vehicles per hour, with a range of 300 vehicles per hour. When the flows are converted to passenger car equivalents, the maximum measured volume still varies by 300 vehicles per hour. The differences are dependent on a number of variables; several are listed in Table 2.5, as well as information about how these variables impact capacity. Unfortunately, capacity is partially dependent on driver behavior, and behavior is always going to have a certain amount of uncontrollable randomness.

Table 2.4. Highest free-flow measurement before queuing initiated

Table 2.5. Variables known to impact work zone capacity

There are also two different measures of capacity at lane closures and restriction. Table 2.4 shows the maximum flow immediately before queuing occurred (uncongested flow). For the purposes of estimating queue length and delay once queuing has occurred, the queue discharge rate is probably more important than the maximum uncongested flow rate. To understand how the two are different, a graph of the data taken in the work zone on I-80 near Davenport, Iowa, is shown in Figure 2.3.

Figure 2.3. Volume and speed distribution before, during, and after a work zone queuing event

Figure 2.3 shows volume counts (at the top of the graph), average speeds (at the bottom of the graph), and vertical lines indicating when in time queuing started and when queuing dissipated. Each data point is the average of a five-minute period. Note that there is a precipitous drop in speed at the beginning of queuing and an increase in speed as soon as queuing ceases. Also, note that volumes, particularly at the beginning of queuing, decline. What is being observed is a capacity drop. That is, after queuing starts, the capacity of the work zone declines. The capacity after the capacity drop is the queue discharge rate. Thus, if the focus is on understanding the delay and queue length after queuing begins, then the queue discharge rate is needed. If the focus is on avoiding a queue and keeping traffic moving at freeflow, the focus is on the maximum flow rate immediately before queuing occurs. To keep traffic moving through the work zone efficiently, a traffic manager might employ metering or diversion strategies to keep the flow below the maximum throughput before queuing begins.

Microscopic Simulation (without network trip distribution capabilities)

Microscopic simulation generates vehicles as individual entities operating within the simulated environment. Each vehicle (entity) is assigned properties and moves through the traffic stream following predefined rules. The interaction between vehicles is defined by car-following and lane-change algorithms. Very popular microscopic simulation packages include the Federal Highway Administration’s CORSIM software package and SimTraffic, part of the Synchro software package (other software packages with trip distribution capabilities will be discussed later) (35,36). Both of these software packages have no capabilities to distribute trips through the network independently of the operator’s input. As a result, the operator must input traffic patterns, including turning movements at intersections. In other words, to understand the network impacts (diversions of traffic to alternative routes), the modeler must input changes to the traffic patterns to estimate network impacts of work zone-caused lane restrictions. Because these software systems do not have dynamic trip assignment capabilities, it is difficult (or impossible) to model dynamic traffic impacts in complex networks.

To overcome these difficulties, Anderson and Souleyrette integrated CORSIM with Tranplan (a regional travel demand model) (37). Tranplan includes a macroscopic model that distributes trips through the network based on link travel times. The process starts with the initial travel patterns, the travel times experienced by traffic are estimated using CORSIM, and then the travel times are fed back into Tranplan and the trips are redistributed to the network based on the travel time provided by CORSIM. The new trip distribution is fed into CORSIM and the link travel times are re-estimated. The two models interact with each other until the flow on links in the network converged to a constant volume. This was a clumsy method to get around the weakness of CORSIM.

Schnell and Aktan compared the results of CORSIM and SimTraffic’s simulation results for traffic delay and work zone queue length in Ohio to the actual performance measured in the field. They found that CORSIM and SimTraffic’s estimates of queue length were less precise than more simple models like QUEWZ (38). This is partially because the car-following algorithms and lane-change algorithms used in CORSIM were not developed for the work zone environment. However, in a later paper, Chitturi and Benekohal compared QUEWZ, FRESIM (the freeway simulator in CORSIM), and Quickzone and found that none of these programs offer accurate estimates of queue length at work zone restrictions (39).

Microscopic Simulation (with network trip distribution capabilities)

Advanced microscopic traffic simulators are available that have dynamic assignment capabilities. Several microscopic simulation software packages have dynamic trip assignment capabilities that make them an ideal environment for measuring the network impacts of work zone-related lane closures. We found no literature identifying a comprehensive list of applications of microscopic simulation with dynamic assignment capabilities for the analysis of work zones in complex highway networks. One of the first known largest applications was used to study the traffic impacts of the reconstruction of I-15 through Salt Lake City in the late 1990s. The Salt Lake City study used a simulation software package with dynamic trip assignment named INTEGRATION (40). After the death of the developer of INTEGRATION, Michel Van Aerde, in 1999, other software packages have evolved that provide much better graphical output and easier to use interfaces.

SMARTEST, a European commission project, was completed in 1997. At the time, the researchers identified 56 microscopic traffic simulation packages and evaluated 32 of these packages (41). Since then, more simulation packages have been created, but the ones that seem to be gaining the most commercial success are AIMSUN (developed by TSS, Barcelona), DRACULA (University of Leeds/WS Atkins), HUTSIM (Helsinki University of Technology), Paramics (SIAS & Quadstone, Edinburgh), and VISSIM (PTV, Karlsruhe). This is the opinion of Ken Fox, a simulation expert (42). All of these packages have dynamic trip assignment capabilities. These systems have much more robust capabilities than SimTraffic or CORSIM, but they also require more user inputs, are more labor-intensive to set-up, and require more expertise to use.

Another advanced microscopic simulation package, MITSIM, is being used by the Iowa DOT and the Des Moines Metropolitan Planning Organization (MPO) to model the traffic impacts of I-235 reconstruction in Des Moines (43). MITSIM is a product of the Massachusetts Institute of Technology’s MITSIMlab. The MITSIMlab is a laboratory for evaluating the impacts of alternative traffic management system designs at the operational level and assisting in subsequent refinement. The model was implemented by the Iowa DOT’s consultant Jacobs Civil Inc. and is operated by the Iowa DOT and Des Moines MPO. To date, no evaluation has been performed of the MITSIM application in Des Moines.

Chapter 3. STATE AGENCY SURVEY SUMMARY

A survey of state transportation agency (STA) practices and policies used to manage work zone safety and mobility impacts was conducted. The survey was conducted through the use of a structured outline for a telephone interview. The respondent was first sent a copy of the outline and then a telephone interview was conducted. Interviews varied in length, lasting anywhere from ten minutes to an hour. A copy of the interview outline can be found in Appendix A.

Methodology

Our team of researchers began the survey process by contacting state traffic engineers. Often, we were referred to other individuals within the agency that would assist the researchers in answering the survey questions. During the interview, questions were asked to lead the interviewee to a better understanding of the agency’s practices. Although the interview was intended to cover all stages of project development—from project concept to postmortem—the interview often focused on the issues with which the respondent was most familiar. For example, if the individual interviewed was responsible for production of maintenance of traffic plans, then the discussion might focus on scheduling and phasing of construction to accommodate traffic control in the design phase, rather than covering topics the respondent was unfamiliar with during early project development or during system planning. A short report was developed from the findings from these interviews. The report was then returned to each respondent to let him or her modify and comment on the description of the STA’s practices and to ensure accuracy of the report.

Figure 3.1 is a map showing surveyed states. The survey was conducted on thirty states. The number thirty was selected as a stopping point because of resource limitations. The decision whether to interview a state or not was purely arbitrary and partly related to whether the research team had contacts in a state.

Figure 3.1. Surveyed states

The goal for developing the interview outline was to cover strategies used to manage work safety and mobility impacts at each step in the project development process. Figure 3.2 shows a simplistic representation of the fundamental steps of project delivery. Each STA may have different names for each step or have steps more finely divided; however, fundamentally, all highway project development follows the same process. Our purpose in this document is not to explore the development process (what goes on in each of the boxes), but rather to determine actions and plans that the STAs take at every step in the project development process to minimize work zone-related congestion and safety impacts. As individual STAs are discussed, it can be seen that STAs do make decisions and plans regarding work zone safety and mobility at every stage of project development. Very few of the interviewed STAs take into account work zone safety and congestion impacts at all stages of project development. Some of the best practices were found in states that focused on the evaluation of impacts at one step and then did an extremely good evaluation during that step. For example, a couple of states have extremely good processes for documenting the performance of the work zone during construction and then using this information to adjust the work zone and develop postmortem reports on what worked well and what did not work.

Figure 3.2. Generic project development process

The diagram shows the project development flow as a linear series of sequential steps, and the project development process for routine projects may linearly flow along this sequence of steps. However, for large and complex projects, the flow is less likely to be linear and may involve some backtracking of steps or modification to take into account issues that are outside of the control of design professionals. An example might be a large-scale reconstruction project that enters final design as a traditional design-bid-build project and is scheduled to take six years to complete. Given the impacts to the community, local business leaders ask the STA to rethink the schedule and shorten the duration of reconstruction. In the process of re-examining the project, the STA backtracks and delivers the project using design-build and reduces the schedule to three years to complete.

Large and complex projects often require significant traffic mitigation efforts (5 to 10 percent of the cost of the project). Because mitigation efforts have significant impacts on project budgets, the cost of the mitigation must be factored into financial plans prior to program planning.

One part of the project development process that is commonly confused is the difference between the project delivery method and the contractor selection methodologies and contractor incentives/disincentives. The two common delivery methods are design-build and design-bid-build, and these methods often get confused with methods used to provide contracts incentives or disincentives to minimize the impacts of their work. Although incorrect, design-build and contracting incentives/disincentives are commonly referred to as innovative contract methodologies. Both may seek the same objective—to shorten the project delivery schedule, but design-build is a project delivery method, while incentives/disincentives are contracting methods. The diagram in Figure 3.2 clearly shows that design-build takes a step out of the project developing process.

The focus of our survey was to identify policies, processes, and practices that STAs have developed and other STAs may wish to consider adapting and adopting when attempting to develop a Transportation Management Plan for a work zone under the new FHWA rule on work zone safety and mobility. Responses to the survey were routinely short, and often respondents explained that they would like to have more comprehensive processes for considering and mitigating work zone impact but resources were limited. However, almost every state was typically proactive in a specific area in which the respondent gave valuable insight on the STA’s activities.

Once the practices of interest were identified, the researchers requested additional information. The result is the following summary of practices and policies that state agencies are currently completing to reduce congestion and improve safety in construction areas.

Responses by State Agency

Arizona Department of Transportation[2]

The Arizona Department of Transportation (ADOT) considers practices to reduce congestion at the system planning phase. Currently, the ADOT considers the congestion impacts at the system planning stage for complex urban projects where the scheduling of work on parallel or nearby corridors simultaneously would multiply the resulting congestion. The ADOT is creating a policy that will address congestion and safety on all projects as part of the new FHWA Rule 23 CFR part 630, “Work Zone Safety and Mobility.” The ADOT has observed that through additional construction planning projects in the urban centers of the state, congestion and safety in work zones can be better managed.

During design, the ADOT balances queue lengths and traveler delay with lane occupancy. The ADOT uses traveler delay cost to choose the number of lanes that can be closed during construction. Also, through the use of QUEWZ, a work zone traffic operations computer model, the ADOT makes decisions regarding the need and type of congestion mitigation. These analyses and decisions are completed on a project-by-project basis rather than through a set policy. The ADOT will also consider the use of full closures, nighttime work, and alternative phasing to reduce congestion. Most of the urban projects completed by the ADOT involve nighttime construction. The ADOT may use contractor incentives/disincentives, select contractors through A+B bidding, and use lane rental to reduce project duration and congestion. The ADOT has completed a design-build project in which the ADOT’s objective for selecting the design-build delivery methods was to reduce the duration of the project. Because the project had only been recently completed, the interview respondent could comment on ADOT’s experience with design-build method.

The ADOT has been very proactive in using a work zone evaluation process to improve existing work zones and to modify future work zone traffic management plans. The ADOT uses a work zone checklist created to assist the project engineer with analyzing the traffic control plan and evaluating the work zone on a daily basis. The ADOT trains these inspectors in two eight-hour work zone class sessions. Each inspector must complete both sessions prior to the construction season. This checklist evaluates each work zone for possible hazards, concerns, and lessons learned. The results of these evaluations are then distributed to offices involved in the project delivery process to help them improve the management of congestion and safety in future projects.

Arkansas State Highway and Transportation Department[3]

The Arkansas State Highway and Transportation Department (AHTD) considers congestion and safety impacts of work zones when it is programming construction and during design. During this period, the AHTD considers driver delay costs associated with closing routes and with traffic volumes, and adjusts phasing and scheduling to reduce congestion. The AHTD does not have a specific threshold for queuing what they consider unacceptable. Instead, the experience of their traffic control engineers is used to determine when a lane closure is likely to create an unacceptable condition. The AHTD has used QUEWZ and CORSIM, a traffic simulation package, to examine traffic operation in special cases.

The AHTD also considers construction schedule methods such as full closures, nighttime construction, and alternative project phasing and builds into its contracts incentives/disincentives to manage congestion and reducing project duration through A+B bidding for contractor selection, lane rental, and liquidated damages. Alternative contracting incentives/disincentives are selected based on the conditions of the project and on their ability to reduce driver delay. The AHTD believes that using contractor i