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Traffic Management

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Traffic management is an extremely important part of any roadway construction project whether it be maintenance through bonded concrete overlays, rehabilitation through unbonded overlays, or full reconstruction into a new concrete pavement. Traffic management is much more than traffic control within the work zones of these various methods; it is a broad umbrella approach that involves long-range strategies for moving people and goods safely and efficiently through a corridor.

With the extreme demand increases on the United States' roadway infrastructure, many agencies have resorted to limiting the hours when work is permitted leading to night work and restrictions on lane closings. Traffic management strategies that seek to minimize the disruption to a project by increasing the project's duration may be counterproductive and unwise in terms of safety and productivity. A national quality review done by the Federal Highway Administration (FHWA) found that, given a choice, the public normally prefers a short project with major disruptions to a long project with smaller disruptions, which produced the phrase, "get in, get out quickly, and stay out"[1].

Successful traffic management reduces exposure in work zones by reducing the volume of traffic through, length of time, and frequency of the work zones. A proper traffic control strategy can be selected through a five-step process outline in the sections below. In some critical traffic situations, the use of concrete pavement has been rejected because of myths about the curing and construction times for concrete. These steps, combined with the use of fast-track methods make concrete a viable and practical alternative for any application.

Background - Need for Traffic Management

Rehabilitation of today's highways requires traffic management, contracting and construction techniques that are quick and efficient and that result in a pavement with superior rideability and service life. Work zone traffic management (WZTM) involves a comprehensive series of actions designed to minimize motorist delays while enhancing the safety of the motorist and the highway worker.[2] WZTM encompasses safety, mobility, quality, team work, customer focus, asset management, intermodulism, intelligent transportation systems (ITS), technology transfer, longer lasting materials, performance based specifications, innovative contracting, life-cycle costing, traveler/traffic information, and incident management.

In the American Concrete Pavement Association (ACPA) publication, "Creating a New Generation of Pavements,"[3] it is stated that "...as stakeholders have become increasingly dependent on our transportation system, they have become more aware and less tolerant of delays, performance problems, and the expense of poorly constructed and maintained pavements." The ACPA is committed to five goals for concrete research and innovation. These are:

  1. Discerning the best of today's practices.
  2. Reducing initial costs, without compromising pavement performance.
  3. Reducing user delays and public inconvenience associated with construction and maintenance.
  4. Developing cost-competitive options for all paving applications.
  5. Increasing the certainty that concrete pavement will achieve design expectations.


In the past, the use of concrete pavement was rejected for some rehabilitation projects due to myths about how concrete must be constructed. For example, one widely-held myth is that concrete must cure for days before being opened to traffic. A number of agencies specify a cure interval of 5 to 14 days for conventional concrete paving.[4] This myth would dictate that concrete not be used where the pavement must be reopened quickly to reduce motorist delay and inconvenience. In fact, some high early strength concrete can be open to traffic in just 6 to 8 hours. A number of concrete pavement and traffic management myths are shown in Table 1.

Concrete Pavement and Traffic Management Myths
Concrete takes a long time to open to traffic.
Concrete pavement rehabilitation takes a long time to accomplish.
Costs are greater for concrete pavements than for asphalt pavements.
Concrete pavements require different traffic management considerations than asphalt I pavements.
Fast track concrete deals only with materials.
Concrete is too difficult to build or repair.
Concrete pavements are too noisy in the car and along the road, and ride quality is poor.
Regarding the duration and impact of a project, it is better to inconvenience the public only a little even if it takes longer to finish. (...or, it is always preferable to impact traffic a little over a long time rather than to a greater extent for a short time.)
Construction traffic should not drive on the subgrade ahead of concrete placement.
If the road is opened to traffic too soon, the durability of concrete will be worse.
Safety issue - The slower the traffic goes through a work zone, the safer the work zone is for I public/workers.

Innovative Contracting Procedures

A number of innovative contracting procedures have been developed to ensure consideration of road user costs in rehabilitation projects. For example in A + B bidding, a contract is not awarded solely on the basis of the low project cost (A cost), but also based on the contractors estimate of the number of days to complete the project times the daily road user cost. Depending on the magnitude of the daily road user cost, (B multiplier), the number of days bid can play a major role in the award of the contract. Other innovative contracting procedures include lane rental, warranties, and design/build. Each of these is discussed later in this handbook.

Congestion Costs

The Road Information Program Report, "How the Highway Trust Fund Has Changed and the Impact on Road and Bridge Funding Needs," states that since 1973, vehicle-miles driven has increased by 84 percent while in the same period the total highway mileage has increased less than 3 percent.[5] Increased traffic volumes complicate the traffic management process for roadway construction projects. A recent 26 state quality improvement review was conducted by the FHWA to assess the effectiveness of FHWA and State DOT's policies and procedures to enhance safety, improve mobility, and increase the efficiency of the NHS by reducing traffic congestion and delays in construction and maintenance work zones.[6]

The quality improvement review stated that the total cost of congestion in 1993 in the nation's 50 largest metropolitan areas was approximately $51 billion, a 6 percent increase from 1992. The plan also states that the daily road user delay costs on many urban freeway reconstruction projects has been calculated to be well over $50,000 per day!

A project to replace an elevated section of I-45 in Houston, Texas had calculated user costs of over $250,000 per day during the first phase of construction.[7] An incentive of $53,000 per day was used by the Texas DOT to speed completion of this project. This was the largest incentive/disincentive amount used in Texas to that date.

Traffic management strategies that seek to minimize the disruption of a project by increasing the project's duration, may be counterproductive. Limiting contractors to single lane closures or to nighttime work hours has in some cases proven to be unwise in terms of both safety and productivity. Workers are less productive and there is more exposure of workers to traffic and traffic to hazards, such as drop-offs. Maintenance contracts have actually been awarded that only allowed the contractor to work one day a week.6 The national quality review, mentioned above, found that given a choice, the public normally prefers a short project with major disruptions to a long project with smaller disruptions. In recent projects, high traffic volume routes have been closed to allow a major phase of work to be accomplished quickly and have shortened the project duration by as much as a year.


Fast-Track Concrete Pavement Construction

Fast-track concrete pavement construction entails many methods for accelerating construction. Contractors and agencies must make some changes to traditional construction specifications and processes to build a fast-track project. The changes not only include the use of high-early-strength (fast-track) concrete, but can also alter opening criteria, construction staging, joint construction, and worker responsibilities. Fast-track can be used throughout the project or only at critical locations, such as intersections and crossovers. Fast-track techniques can be used for new construction, reconstruction, or resurfacing projects.

Fast-track concrete pavements are proven to:

  • Allow engineers to consider concrete for projects thought unfeasible because of lengthy concrete cure-times.
  • Perform under many different traffic and application conditions.
  • Expedite construction and ease work zone congestion during major highway restoration, resurfacing or reconstruction.
  • Shorten the time before residents and businesses can have normal access to their homes and businesses.
  • Allow agencies to rebuild intersections instead of resurfacing them to cover up rutting, raveling, corrugation and other safety problems.


Public Information

Public information is essential to gaining public support for a specific project and for highway construction in general. In the planning stages of a project, the public should be presented options on how the project is to proceed. It is also important to communicate with business owners and public service providers affected by the project. After work begins, information to the public about the progress of the project and upcoming phases are also important. Some contractors produce newsletters to keep the public informed as the project progresses. Project engineers are sometimes being called on to give television or radio reports on the project's status.

Fundamentals of Traffic Management for Concrete Pavement

This section reviews definitions of terminology and the fundamental principles from Part VI of the Manual on Uniform Traffic Control Devices (MUTCD) [8] as they relate to strategy selection and the types of work zones that may be specified as part of a concrete pavement project. Myths, time and space requirements, and life-cycle cost analysis are also discussed.

Definitions

Work zone traffic management is much more than traffic control in the work zone; it is a broad umbrella approach that involves long-range strategies for moving people and goods safely and efficiently through a traffic corridor.

In the most basic terms, strategies are the different ways to accomplish an objective. Strategies must be selected when there are two or more competing interests. In work zones these two interests are: first, the traffic and how it is handled, and second, the concrete pavement work and how it is done. These both cost time and money. If only the pavement rehabilitation was important, the cheapest and fastest manner to build the job is to eliminate the traffic from the work space. Of course, if only the traffic was important, then work could be limited to maximize the safe and efficient movement of traffic. But when both interests are present, what is the best way to accomplish the objective? In reality there are a number of interests, including political and community interests.

The best strategy for a specific project is the strategy that optimizes the relationship between project cost, societal costs (costs to the community), highway safety, and traffic management. Once the strategy or strategies are selected for a project, they are then translated into traffic control plans and contract requirements. Designers with a good understanding of the common strategies can develop traffic control plans and contract requirements to optimize the cost and effectiveness of construction, traffic management, motorist convenience, and community/social needs.


On simple projects, the most common strategies are represented by the typical applications in Part VI of the MUTCD. (These are plans that show a roadway and the locations of work zone traffic controls on that roadway.) As projects become more complicated and different restrictions or limitations are included in the planning process, the strategies will become more involved and may employ many methods of both traffic control and construction management.

The types of rehabilitation work include restoration, resurfacing, and reconstruction,[9] which are defined as follows:

Restoration - Full and partial depth concrete repair (patching) and joint and crack resealing, dowel bar retrofit, diamond grinding and adding shoulders.

Resurfacing - Overlays of the pavement that can provide a new riding surface, correct surface irregularities, and increase the structural capacity of a pavement. Includes whitetopping (conventional and ultrathin) and bonded and unbonded overlays.

Reconstruction - Complete removal of the pavement structure, typically including the base layers, which are replaced with a new pavement or inlay. Includes capacity and safety enhancements. Widening can involve a combination of these techniques.

References

  1. "Meeting the Customers' Needs for Mobility and Safety During Construction and Maintenance Operation," NQI Survey, Federal Highway Administration, Washington, DC, 1997.
  2. "Meeting the Customers' Needs for Mobility and Safety During Construction and Maintenance Operation," NQI Survey, Federal Highway Administration, Washington, DC, 1997.
  3. "Creating a New Generation of Pavements," American Concrete Pavement Association, Skokie, IL, 1997.
  4. "Fast-Track Concrete Pavements," TB004.02P, American Concrete Pavement Association, Skokie, IL, 1994.
  5. "How The Highway Trust Fund Has Changed and The Impact on Road and Bridge Funding Needs," The Road Information Program, from Better Roads, March 1998.
  6. "Meeting the Customers' Needs for Mobility and Safety During Construction and Maintenance Operation," NQI Survey, Federal Highway Administration, Washington, DC, 1997.
  7. Beng, Ferno, and Voigt, "Accelerating Major Freeway Reconstruction Projects: The Houston Experience," Paper presented at 1998 Transportation Research Board Annual Meeting, August 1997.
  8. Federal Highway Administration, "Part VI—Standards and Guides for Traffic Controls for Street and Highway Construction, Maintenance, Utility, and Incident Management Operations," Manual on Uniform Traffic Control Devices. 1998 Edition, Revision 3, U.S. Government Printing Office, Washington, D.C., September3, 1993.
  9. "Pavement Rehabilitation Strategy Selection," TB-015.P American Concrete Pavement Association, 1993.