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21st Century Operations Using 21st Century Technologies

Active Traffic Management Feasibility and Screening Guide

Chapter 7. Next Steps

Completing the ATM feasibility and screening process, as discussed in the previous chapters, is just the beginning. At this juncture, agencies can use the results from the screening process for two general directions:

  • Agencies use the screening results to present business cases to their management to obtain funding for follow-on activities associated with the systems engineering and broader project development process, including the immediate steps of developing ATM Concepts of Operations and the environmental/National Environmental Policy Act (NEPA) process as may be required.
  • Agencies use the screening results for planning purposes to create ATM deployment programs and/or strategic plans providing a blueprint for ATM in the region or for a particular agency. These plans can be incorporated into the regional transportation planning process, including the regional long-range transportation plan, Regional ITS Architecture, and/or regional and/or statewide transportation improvement plans.
  • Consideration should also be given as to how the ATM screening results fit into the broader ATDM concept, including whether there are any parallel Active Demand Management (ADM) and/or Active Parking Management (APM) efforts or initiatives in the region, and how those efforts could work in concert with future ATM deployments.

This chapter does not provide guidance on developing a Concept of Operations for ATM or for incorporating ATM in the regional or agency transportation planning processes; several references and examples are available to guide the practitioner in this regard. Rather, this chapter highlights a few key issues that will need to be addressed during these next steps, the knowledge of which will be of use while applying the initial screening guidance.

7.1 Stakeholder Involvement

Engaging with stakeholders as part of the screening process is discussed in Chapter 2. This is a continuing process, and regardless of which direction an agency takes, the number of stakeholders and the need for interaction will increase. Moreover, the driving public will become an important stakeholder requiring public outreach and education activities to help ensure they fully understand the ATM operational concepts.

7.2 Performance Measures

Performance measures indicate how well the transportation system is performing and are inextricably tied to operations objectives. Developing performance measures is an integral part of the objectives-driven, performance-based approach to planning (as shown in previous Figure 1). The performance measures selected should provide adequate information to planners, operators, and decision-makers on progress toward achieving their operations objectives.(2)

ATM-related performance measures will likely be necessary for both the planning process and Concept of Operations. Should detailed analyses be performed via simulation, the performance measures should guide the modeling process. Performance measures will also be critical to monitoring the performance of the implemented ATM strategies, thereby allowing operators to make tweaks to implemented strategies to maximize benefits they offer. Moreover, the ability to expand coverage of ATM strategies may largely hinge on the ability to both monitor ATM strategies and demonstrate that strategies work toward meeting regional transportation goals.

A number of potential measures of effectiveness are identified in the literature. The Active Traffic Management Guidebook (4) identifies the following examples of performance measures used in European ATM deployments:

  • Speed differential between lanes.
  • Duration of speed less than x mph.
  • Frequency of speed less than x mph.
  • Flow and/or speed plots.
  • Lane utilization.
  • Headway distribution.
  • Vehicle speed distribution.
  • Vehicle hour delay.

The Guide for Highway Capacity and Operations Analysis of Active Transportation and Demand Management Strategies (47) recommends four measures of effectiveness for evaluating the achievement of one or more ATDM objectives. These measures, as identified in the reference, are computed across all of the scenarios to obtain overall results:

  • Person miles traveled is a measure of the productivity of the highway system in terms of the number of people moved by the system and the number of miles they are moved.
  • Average system speed (mph) is a measure of the efficiency of the highway system, and it is computed by adding the vehicle miles traveled (VMT)-served for each scenario and then dividing by the sum of the scenario vehicle hours traveled (VHT), including any vehicle entry delay. A key objective of ATDM is to maximize the system's productivity, serving the greatest amount of VMT at the least cost to travelers in terms of VHT. Thus, changes in the average system speed are a good overall indicator of the relative success of the ATDM strategy at achieving its objective of improving efficiency.
  • The average delay per mile traveled is useful for conveying the results in a manner that can be related to personal experience. The average delay is measured in terms of vehicle- seconds delay per VMT.
  • The planning time index (PTI) is a measure of the reliability of travel times on the facility. It is the ratio of the 95th percentile highest predicted travel time to the free-flow travel time. For example, a PTI of 1.20 means that the traveler must allow 20 percent extra time over free-flow travel time to get to their destination on time with a 95 percent level of confidence.

Another ATM performance measure of great importance is safety. Potential before and after performance measures in this regard include the following:

  • Crash rates (by crash type).
  • Number of crashes per segment.
  • Number of secondary crashes and rates.
  • Number of property-damage only crashes and rates.
  • Number of injury crashes and rates.
  • Percent vehicles exceeding speed limit by x percent.

7.3 Conformance with Regional Intelligent Transportation System Architecture

The initial activity shown in Figure 2, the Systems Engineering Vee Diagram, is the "Regional ITS Architecture." FHWA Rule 940 (23 CFR 940) requires ITS projects that are funded, in whole or in part, with the Highway Trust Fund to conform to the National ITS Architecture and standards. The rule states that "conformance with the National ITS Architecture is interpreted to mean the use of the National ITS Architecture to develop a regional ITS architecture, and the subsequent adherence of all ITS projects to that regional ITS architecture."

The National ITS Architecture identifies a series of transportation services for which transportation systems apply. These transportation services are addressed through 95 unique Service Packages. A Service Package is a group of different subsystems and communication flows needed to deliver a desired transportation service. Service Packages can work separately or in combination to address the real-world transportation needs and desires identified through traditional planning activities. Service Packages directly related20 to the ATM strategies are listed in Table 16. Three of these—ATMS22: Variable Speed Limits, ATMS23: Dynamic Lane Management and Shoulder User, and ATMS24: Dynamic Roadway Warning—were recently created to support ATM and included in the National ITS Architecture as part of Version 7.0 (released in late 2013). Accordingly, while not necessary for the ATM screening process described herein, it may be necessary to update the Regional ITS Architecture to include these ATM-related Service Packages as the systems engineering process continues such that the proposed ATM system, as subsequently documented in the Concept of Operations and Requirements, does indeed "conform" to Rule 940.

7.4 Regulations and Manual on Uniform Traffic Control Devices Standards

The potential for changes in legislation to support certain ATM strategies (dynamic shoulder lanes, dynamic speed limits/displays) has been previously noted. ATM signage and procedures, particularly for dynamic lane assignment and possibly dynamic speed limits, as used in Europe and in the initial ATM implementations in the United States are not currently described in the MUTCD. This is particularly the case for DLA displays to alert drivers that a lane is closed downstream and that they should merge left or right.21

Name Description
APTS09 Transit Signal Priority Determines the need for transit priority on routes and at certain intersections and requests transit vehicle priority at these locations.
ATMS03 Traffic Signal Control Provides the central control and monitoring equipment, communication links, and the signal control equipment that support traffic control at signalized intersections. A range of traffic signal control systems are represented by this service package.
ATMS04 Traffic Metering Provides central monitoring and control, communications, and field equipment that support metering of traffic and supports the complete range of metering strategies including ramp, interchange, and mainline metering.
ATMS06 Traffic Information Dissemination Provides driver information using roadway equipment, such as dynamic message signs.
ATMS07 Regional Traffic Management Provides for sharing traffic information and control among traffic management centers to support regional traffic management strategies.
ATMS09 Transportation Decision Support and Demand Management Recommends courses of action to traffic operations personnel based on an assessment of current and forecast road network performance
ATMS18 Reversible Lane Management Provides for the management of reversible lane facilities; also includes the equipment used to electronically reconfigure intersections and manage right-of-way to address dynamic demand changes and special events.
ATMS19 Speed Warning and Enforcement Monitors vehicle speeds and supports warning drivers when their speed is excessive; also the service includes notifications to an enforcement agency to enforce the speed limit of the roadway.
ATMS22 Variable Speed Limits Sets variable speed limits along a roadway to create more uniform speeds, to promote safer driving during adverse conditions (such as fog), and/or to reduce air pollution; also known as speed harmonization.
ATMS23 Dynamic Lane Management and Shoulder Use Provides for active management of travel lanes along a roadway, including the associated hardware and control electronics that are used to manage and control specific lanes and/or the shoulders.
ATMS24 Dynamic Roadway Warning Includes systems that dynamically warn drivers approaching hazards on a roadway (e.g., roadway weather conditions, road surface conditions, traffic conditions including queues, obstacles or animals in the roadway and any other transient event that can be sensed).
MC08 Work Zone Management Manages work zones, controlling traffic in areas of the roadway where maintenance, construction, and utility work activities are underway.

Steps for experimental approval should be taken when a project timeline is set to ensure approval when the system will be activated. Per the MUTCD,(49) "a successful experiment is one where the research results show that the public understands the new device or application, the device or application generally performs as intended, and the device does not cause adverse conditions. The 'experimenter' must evaluate conditions both before and after installation of the experimental device and describe the measurements of effectiveness (MOEs) of the safety and operational benefits (e.g., better visibility, reduced congestion)." The request for experimentation should originate with the agency and be sent to the FHWA MUTCD Team with a courtesy copy to the local FHWA Division Office. The FHWA must approve the experiment before it begins. All requests should include the following information:

  • A statement of the nature of the problem, including data that justifies the need for a new device or application.
  • A description of the proposed change, how it was developed, and how it deviates from the current MUTCD.
  • Any illustration(s) that enhances understanding of the device or its use.
  • Supporting data that explains how the experimental device was developed, if it has been tried, the adequacy of its performance, and the process by which the device was chosen or applied.
  • A legally binding statement certifying that the concept of the traffic control device is not protected by a patent or copyright.
  • The proposed time period and location(s) of the experiment.
  • A detailed research or evaluation plan providing for close monitoring of the experimentation, especially in the early stages of field implementation, including before and after studies as well as quantitative date enabling a scientifically sound evaluation of the performance of the device.
  • An agreement to restore the experimental site to a condition that complies with the provisions of the MUTCD within 3 months following completion of the experiment. The agreement must also provide that the sponsoring agency will terminate the experiment at any time if it determines that the experiment directly or indirectly causes significant safety hazards. If the experiment demonstrates an improvement, the device or application may remain in place until an official rulemaking action occurs.
  • An agreement to provide semiannual progress reports for the duration of the experimentation and a copy of the final results to the FHWA's Office of Transportation Operations within 3 months of the conclusion of the experiment.

FHWA recently completed a project to evaluate ATM sign displays and to identify potential gaps in the MUTCD in this regard. The project is completed, but the findings and recommendations are still being reviewed by the TMC Pooled Fund Study and FHWA, and have not been released to date.

Shoulder lanes and junction control strategies may also require FHWA approval for design exceptions and modifications once a shoulder is turned into a travel lane. These may include the following:

  • Safety clear zone offset distance to hazards (since the travel lane will be pushed out 12 feet further). A common mitigation measure is to add and/or modify protective barrier.
  • Vertical clearance (bridges on a grade may not have full clearance over what was once the shoulder).
  • Stopping sight distance (in particular, around horizontal curves where the new travel lane is in close proximity to barrier wall).
  • Lane width (e.g., 10-foot shoulder used as DShL).
  • Drainage.
  • Pavement structure (was the shoulder pavement constructed sufficiently to accommodate the new design load if used as a temporary travel lane).

Deploying dynamic shoulder lanes and junction control may require expanding the roadway footprint for widening the shoulders and to accommodate pull-out refuge areas. By moving traffic closer to the edge of the right-of-way, noise might increase near the right-of-way. In these circumstances, developing environmental assessments and/or environmental impact statements in accordance with the National Environmental Policy Act (NEPA) process might be necessary; this is an activity that should be included in the cost estimate.

7.5 The Future

One of the early activities in the ATM feasibility and screening process is reviewing recent literature on ATM strategies—from the United States and abroad—to determine whether any new approaches, guidelines, and/or standards have come to light that might impact or otherwise influence the screening process as described herein and any subsequent design activities. There has been an often rapid evolutionary path in the design and operational approaches for several ATM strategies, such as sign displays and layouts, the spacing of sign gantries and supports, operating algorithms and automated decision support mechanisms, and the associated real-time data needs. Moreover, several ATM strategies are in their relative infancy in the United States, and there will undoubtedly be many lessons learned and new requirements (e.g., MUTCD standards for lane control and dynamic speed displays, updates to the National ITS Architecture, and use of automated speed enforcement) as ATM matures in this country. Such future developments will impact not only the feasibility screening but also ATM design and operations. It is most important that the practitioner be aware of any such future developments when looking at potential ATM strategies and the optimum roadway locations.

There is also the long-term future of a connected vehicle environment and its potential impact on ATM. There are many possibilities in this regard—for example, data that permits better short-term predictions of congestion and safety concerns and real-time environmental data that are used to dynamically change speed limits and signal timing to minimize emissions. Who knows, but in-vehicle displays and automated vehicles may completely eliminate the need for ATM infrastructure signs altogether sometime in the distant future. But that is the subject of another Guidance document years from now.

20 Other Service Packages support ATM operations, including, but not limited, to, surveillance, incident management, road weather data, work zone management.

21 Washington State uses a yellow downward diagonal arrow. Minnesota uses yellow chevrons pointing left or right.

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