Active Traffic Management (ATM) Implementation and Operations Guide

CHAPTER 1. INTRODUCTION

Transportation professionals continue to be challenged by congestion and safety on the complex networks they build, operate, and maintain. As recurring and nonrecurring congestion increase, travelers experience longer delays, consume more fuel, and feel the impact of more crashes on their daily commutes. Agencies recognize that adding capacity is frequently outside the realm of both physical and fiscal possibility. Thus, they increasingly turn to transportation systems management and operations (TSMO) strategies to mitigate mobility and reliability impacts. Over the past two decades, agencies have explored a variety of approaches that have yielded improved freeway management, arterial management, regional coordination, and integrated corridor management. Today, most agencies have levels of operational capability, detection, and information dissemination mechanisms that would have been unimaginable two decades ago. As a result, agencies are able to leverage these investments and capabilities through the application of a wide variety of approaches to improve mobility and safety. However, agencies continue to face the challenges of changing travel patterns, growing demand, evolving traveler behaviors, limited financial resources, and increasing traveler expectations.

Active transportation and demand management (ATDM) is an agency's capability to improve trip reliability, safety, and throughput of the surface transportation system by deploying operational strategies that dynamically manage and control travel and traffic demand and available capacity, based on prevailing and anticipated conditions.⁽¹⁾ Through the use of available tools and assets, agencies manage traffic flow and work to influence traveler behavior in real time to achieve operational objectives, such as preventing or delaying breakdown conditions, improving safety, promoting sustainable travel modes, reducing emissions, and/or maximizing system efficiency. ATDM can include multiple approaches spanning demand management, traffic management, and parking management.

Active traffic management (ATM) is one of the three categories of strategies under ATDM, along with active demand management (ADM) and active parking management (APM). ATM encompasses a broad array of nontraditional solutions that agencies can deploy to increase the efficiency of their transportation facilities. This efficiency is accomplished by moving from static approaches to more actively and dynamically managed traffic operations, which work to match fluctuating demand and varying conditions. As transportation agencies grapple with increasing congestion and fewer available funds to add capacity, temporary and permanent ATM strategies have been increasingly deployed in the United States within the last decade.

Active traffic management includes nontraditional solutions to increasing the efficiency of transportation facilities through actively and dynamically managing traffic operations.

The Federal Highway Administration (FHWA) has developed this ATM Implementation and Operations Guide (the Guide) to assist transportation agencies interested in implementing ATM in their region, as well as those already operating ATM systems, in the pursuit of more efficient use of their networks through the implementation and operation of ATM strategies.

This chapter provides a quick guide to the topics covered in the individual chapters of the guidebook and the format used throughout the document. The remainder of this chapter presents the following sections:

• Overview, Goals, Intent, and Audience. This section presents an overview of the Guide, including the goals and objectives for the guidebook and the intent of the document to advance the concept of ATM.
• Overview of ATM Strategies. This section provides a high-level description of the ATM strategies included in the Guide along with application scenarios and examples.
• ATDM, ATM, and TSMO. This section describes the relationship between ATM, ATDM, and the broader TSMO concept.
• Systems Engineering. This section presents the systems engineering process and its importance in the development and implementation of ATM projects.
• Chapters at a Glance. This section provides a quick guide to the major topics covered in each of the chapters and highlights the major elements covered.

1.1 OVERVIEW, GOALS, INTENT, AND AUDIENCE

The objective of this Guide is to provide regional and local agencies with guidance on how to strategically and effectively implement and operate ATM strategies. The Guide describes the stepwise approach to accomplishing this implementation through the application of the system engineering process; comprehensive planning; and organizational considerations, capabilities, and design considerations. It utilizes a combination of relevant existing resources and documents along with best practices and lessons learned gleaned from early adopters to offer practical guidance. It also emphasizes the value of ATM and what these ATM strategies can offer to operating agencies as part of their broader TSMO program.

The intended audience of the Guide includes agencies interested in implementing ATM in their region, as well as agencies that have implemented ATM and are interested in guidance on operating and maintaining their ATM systems and strategies more effectively. It is anticipated that agencies can use the information in implementing new ATM applications while ensuring that their organization and project partners are capable of operating and maintaining the system efficiently. Using the information in the Guide, agencies will be able to step through the implementation process for an ATM project and ensure all aspects of designing, deploying, operating, and maintaining the resulting strategies and systems are supported. This support can include enhanced connectivity and support within a traffic management center (TMC), integration with existing technologies and legacy systems, coordination with partner agencies, and ongoing monitoring of performance measures to enhance operations to support regional goals.

ATM is the dynamic management of recurrent and non-recurrent congestion based on prevailing and predicted traffic conditions. While ATM itself is an evolutionary concept that can theoretically be applied to any existing traffic management application or strategy (e.g., moving from time-of-day shoulder use to dynamic shoulder use), many ATM strategies are relatively new in the United States. More metropolitan regions are interested in implementing one or a combination of ATM strategies based on interest generated from recent deployments in the United States, such as Seattle, Minneapolis, and Northern Virginia.

ATM is the dynamic management of recurrent and non-recurrent congestion based on prevailing and predicted traffic solutions.

As FHWA has conducted ATDM technology transfer workshops and peer exchanges across the country, participating agencies have continued to ask fundamental questions about the implementation and operations of these strategies. Common topics of interest include public outreach and communications; procurement methods; enforcement and whether to make strategies regulatory or advisory; software development; systems engineering; design issues regarding gantry and sign placement; driver comprehension of signs and Manual on Uniform Traffic Control Devices (MUTCD) compliance; ongoing operations and maintenance; required workforce skills, abilities, and supporting institutional business processes; and how to deploy an ATM system today while taking into account a future with connected and autonomous vehicles (CAVs).

While these questions are broadly relevant to TSMO concepts and strategies, they illustrate the need for guidance on ATM strategies and their unique and challenging aspects that differentiate them from more traditional TSMO approaches. Typically, ATM strategies are more dynamic in nature; require higher infrastructure deployment needs; and are more complex with the challenges associated with driver compliance, public outreach, and enforcement.

The Origins and Evolution of ATM

In response to the growing pressure for agencies to do more with less and address congestion challenges from all aspects of the network, FHWA sponsored three international technology scanning studies of Europe in 2005, 2006, and 2010 to examine the congestion management programs, policies, designs, and experiences of other countries that are either in the planning stages, have been implemented, or are operating on freeway facilities. The 2005 scan⁽²⁾ focused on European approaches to demand management, including operational strategies, while the 2006 and 2010 scans focused primarily on active traffic management. The 2006 scan⁽³⁾ sought information on how agencies approach highway congestion and how they are planning for and designing ATM operational strategies at the system, corridor, and project or facility level. The 2010 scan⁽⁴⁾ focused on the geometric design issues associated with ATM.

ATM strategies have been in use internationally for several decades, and the overall success of these strategies prompted their introduction in the United States. Table 1 provides a sample of early-deployment ATM strategies overseas. While not exhaustive, the examples provided show the diversity of ATM strategies in use overseas and from which the United States adapted the strategies included in the Guide.

The concept of ATM has also evolved internationally, both with individual strategies and in combination, with experience. For example, the Department of Transport and Main Roads (DTMR) of the Queensland Government (Australia) has implemented an ATM-related initiative called Managed Motorways. The strategies included in this initiative include dynamic speed limits (DSpL), dynamic lane use control (DLUC) or flexible lane control, adaptive ramp metering (ARM), adaptive traffic signal control (ATSC), dynamic message signs (DMS) with travel time and real-time traveler information, and roadside data systems and sensors.⁽⁵⁾ The traffic management system behind Managed Motorways integrates real-time information into algorithms to predict traffic congestion and proactively respond to conditions.⁽⁵⁾ Enhanced emergency services also improve incident response to improve safety. DTMR indicates that the benefits include reduced congestion, improved travel time reliability, increased capacity, reduced incidents, reduced emissions, and improved fuel efficiency. Similarly, Highways England in the United Kingdom has advanced the concept of Smart Motorways, which is an evolution of previous ATM applications. This concept involves a variety of applications, which include a controlled motorway, hard shoulder running, and all lane running, all of which utilize technology for the purpose of improving journeys and helping ease congestion.⁽⁶⁾

Table 1. Sample early international ATM strategy deployment.⁽⁷⁾

ATM Strategy	Country/Initial Deployment	Documentation Information/Benefits
Adaptive Ramp Metering (ARM)	Germany (1999) The Netherlands (1989)	Reduction in peak-period congestion. Decrease in incidents at ramps. Increase in average speeds during peak.
Adaptive Traffic Signal Control ( ATSC)	Australia (1982) United Kingdom (1981)	Successful at traffic-responsive operations with rapidly changing traffic patterns and demands.
Dynamic Junction Control (DJC)	Germany (1999) The Netherlands (2006)	Reduction in overall mean travel times. Reduction in vehicle delay for both mainline and merging traffic.
Dynamic Lane Reversal (DLR)	The Netherlands (1992)	Originally deployed as a carpool lane. Converted for use by all users after four months.
Dynamic Lane Use Control (DLUC)	Germany (1990s) The Netherlands (1996) United Kingdom (2006)	Frequently used with dynamic shoulder use. Often indicate variable speed limit when needed. Supplemental static signs frequently used.
Dynamic Shoulder Lane (DShL)	Germany (1990s) The Netherlands (1996) United Kingdom (1996) New Zealand (1991)	Frequently used with DLUC. Applications for bus-only lane or all vehicles. Operate on left or right shoulder, but not recommended for both.
Queue Warning (QW)	Germany (1990s) The Netherlands (1983, 1996)	Decrease in crashes, crash severity. Can be combined with DSpL.
Dynamic Speed Limit (DSpL)	Germany (1970s) The Netherlands (1970s) Denmark (2005) United Kingdom (2006)	Decrease in crashes, crash severity. Used in adverse weather and work zones. Slight increase in capacity.

Overall, the European and Australian approach to congestion management programs, policies, and experiences resonates with transportation professionals in the United States. In general:

• Active management is essential to the European and Australian approach to congestion management, building on advancements in technology and traffic management.
• European mobility policy focuses on the traveler, and congestion management strategies center on the need to ensure travel time reliability for all trips at any time of the day.
• Transportation and traffic management operations are priorities in the planning, programming, and funding processes and critical to realizing the benefits of transportation infrastructure investment for congestion management.
• European and Australian agencies use tools to support cost-effective investment decisions at the project level to ensure that implemented strategies have the best benefit-cost ratio and represent the best investment of limited resources.
• European and Australian agencies work to provide consistent messages to roadway users to reduce the impact of congestion on those travelers.
• European and Australian agencies typically include automated enforcement tools when implementing ATM strategies.

Overall, the international experience with ATM has provided direction for the development of ATM within the United States.⁽⁸⁾ Domestic agencies have seen similarities and commonalities in challenges and approaches that can be adapted to fit the needs of the American traveler.

Early ATM Adopters in the United States

Several regions across the country have been adopters of various ATM strategies over the past decade. At the time of installation, these deployments represented state-of-the-art applications, which agencies implemented to help solve the regional mobility and safety challenges. As such, they represent a wealth of experience working to solve the challenges surrounding the planning, design, and implementation of these innovative traffic management solutions with nominal guidance at the time of deployment.

These agencies can provide their experiences in selecting, deploying, monitoring, evaluating, and enhancing various ATM strategies. As these concepts enter the mainstream of congestion management solutions, agencies looking to deploy ATM for the first time can benefit from guidance on how to strategically and effectively implement ATM strategies through the best practices and lessons learned gleaned from these early adopters. Likewise, agencies that have deployed ATM strategies in select locations on their transportation network can benefit from guidance to improve their operations based on the best practices of other agencies. This approach cannot only improve operations at the specific location but also facilitate broader deployment of ATM strategies within the agency's jurisdiction. The following sections highlight early deployment in the United States, though they do not represent an exhaustive list of applications and active deployments.

Washington

The Washington State Department of Transportation (WSDOT) implemented what it terms "smarter highways" on several corridors in Seattle, to include ATM signage used for incident management and roadway maintenance. The system automatically posts regulatory variable speed limits to smooth traffic flow. The first corridor to begin ATM operations in Seattle was a 7-mi segment of Interstate 5 (I-5) northbound from the Boeing Access Road to I 90 in downtown Seattle. With significant construction on the parallel State Route (SR) 99–Alaskan Way Viaduct, ATM signage was implemented to help alleviate increased traffic on the I-5 corridor. Prior to deployment, this corridor averaged 434 crashes per year, 296 of which were congestion related; WSDOT intended for the ATM deployment to reduce property-damage-only crashes by 15 percent and injury crashes by 30 percent.⁽⁹⁾ Figure 1 shows the ATM installation on I-5 in Seattle.

Figure 1. Photo. ATM installation on I-5, Seattle, Washington (Source: Texas A&M Transportation Institute [TTI]).

The second corridor to begin ATM operations was SR 520 in November 2010. This is an 8-mi corridor with 70 new signs at 19 sign locations. This corridor stretches from I 5 to 130th Avenue NE in Bellevue, and originally contained a 2.75-mi gap with no system elements across the floating bridge over Lake Washington that limits the effectiveness of ATM signage operations along the SR 520 corridor. The floating bridge was replaced and now contains an ATM signage gantry midspan. Before deployment, this corridor experienced an average of 379 collisions per year, with 221 being congested related.

Finally, the third Seattle corridor with ATM signage is I-90, a 9-mi corridor from Bellevue to downtown Seattle. Operations began in June 2011 with 129 new signs at 25 sign locations. Prior to deploying ATM signage, this corridor had an average of 330 crashes per year, 200 of which were congestion related. For these deployments, WSDOT typically gathers real-time traffic information to support ATM operations using existing inductive loop detectors and fills the gaps with additional Wavetronix detectors. Side-mounted dynamic message signs (DMSs) are typically on every other gantry on both the left and right side of the highway, with remaining gantries having a standard, larger overhead DMS.

Northern Virginia

One of the newest ATM installations in the country is the Virginia Department of Transportation (VDOT) system along I-66 from U.S. 29 in Centreville to the Capital Beltway (I-495) in suburban Washington, D.C. Completed in September 2015, this project was constructed to improve safety and operations along I-66 by better managing the existing roadway capacity.⁽¹⁰⁾ The deployment includes variable speed limits that are advisory, QW systems, lane use control signs, and DShL. Technologies installed as part of the system include overhead sign gantries, shoulder and lane control signs, speed displays, incident and queue detection, and additional traffic cameras. An overhead sign gantry that is part of the installation is shown in Figure 2.

Figure 2. Photo. ATM installation on I-66, Virginia (Source: VDOT).

The new ATM system along I-66 replaced an older ATM system along the corridor that included static, part-time shoulder use and high occupancy vehicle (HOV) lanes. The older system operated along 6.5 mi of the corridor and allowed general-purpose traffic to use the rightmost shoulders only during peak periods Monday–Friday (eastbound, 5:30 a.m.–11:00 a.m.; westbound, 2:00 p.m.–8:00 p.m.). The installation was a result of the adaptation of the leftmost general-purpose lane to an HOV-2 lane concurrent with the opening of the shoulder lane (eastbound, 5:30 a.m.–9:00 a.m.; westbound, 3:00 p.m.–7:00 p.m.). Advance signage and traffic control signaling provided travelers with information on the operations, including large signs alerting drivers to nine emergency refuge areas. The shoulder was also opened to all traffic during traffic incidents and construction.⁽¹¹⁾

Wyoming

The Wyoming Department of Transportation (WYDOT) first implemented ATM in the form of a variable speed limit (VSL) system along I-80 between Laramie and Rawlins in 2009. This system was implemented to address weather-related closures and to reduce speeds during severe weather and wind conditions.⁽¹²⁾ The rural application incorporated technology to monitor road and weather conditions and visibility with cameras, road and wind sensors, surface and atmospheric conditions, and speeds. Operators in the TMC are responsible for speed selection using the entire available road and weather data and the notifications of any incidents in the corridor. A photo of the VSL signs used in the corridor is provided in Figure 3.

Figure 3. Photo. VSL sign in Wyoming (Source: WYDOT).

WYDOT sets speeds based on reported roadway conditions, including visibility, surface conditions, and current vehicle speeds. Maintenance forepersons or the Wyoming Highway Patrol have the authority to lower speed limits, and there is no limit to the number of times the speed can drop or how long the lowered speeds must be displayed.⁽¹²⁾

1.2 OVERVIEW OF ATM STRATEGIES

ATM strategies work to maximize the effectiveness and efficiency of a facility or network while increasing throughput and safety. Characteristics of these strategies include integrated systems, advanced technology, real-time data collection and analysis, and automated dynamic and/or proactive deployment. Whether implemented individually or as a combination of applications, ATM works to optimize the existing infrastructure. The ATM strategies included in this Guide are shown in Figure 4 and include adaptive ramp metering, ATSC, DJC, DLR, DLUC, DShL, QW, DSpL, and dynamic merge control (DMC).

Figure 4. Graphic. ATM strategies (adapted⁷).

Table 2 provides specific information on each of the ATM strategies for deployment that are addressed in the Guide. Each strategy includes other commonly used names and terms for the strategy, a descriptive definition of the strategy, the operational scenarios that the strategy can address, and the physical geography where the strategy can be applied.

Table 2. ATM strategies for deployment in the United States (adapted ^{7, 13})

ATM Strategy	Definition	Operational Scenarios	Application Geography
ARM (Adaptive Ramp Metering)	The deployment of traffic signals on ramps to dynamically control the rate at which vehicles enter a freeway facility. Utilizes traffic-responsive or adaptive algorithms (as opposed to pretimed or fixed-time rates) that can optimize either local or system-wide conditions.	Recurring congestion; planned special events (PSEs)	Limited-access facilities
ATSC (Adaptive Traffic Signal Control)	The continuous monitoring of arterial traffic conditions and queuing at intersections and the dynamic adjustment of signal timing to smooth traffic flow along coordinated routes and to optimize one or more operational objectives (such as minimize overall stops and delays or maximize green bands). Also known as responsive and/or multimodal preferential signal control.	Variability and unpredictability in demand; excessive delay and stops	Arterials
DJC (Dynamic Junction Control)	The dynamic allocation of lane access on mainline and ramp lanes in interchange areas with high traffic volumes, and where the relative demand on the mainline and ramps changes throughout the day. Through the use of signs, mainline lanes can be closed or become an exit, shoulders can be opened, and so forth to accommodate entering or exiting traffic.	Heavy weaving/merge areas; work zones (WZs); PSEs	Interchanges; on/off ramps
DLR (Dynamic Lane Reversal) Reversible lane; contraflow lane; tidal flow	The reversal of one or all lanes to dynamically allocate capacity of congested roads, allowing capacity to better match traffic demand throughout the day. Lane reversal could include changing the number of available lanes per direction by physically moving barriers or by signage.	AM/PM directional shift in managed lanes and/or arterials; emergency management; PSEs	Limited-access facility; multilane arterials
DLUC (Dynamic Lane Use Control) Dynamic lane assignment	The dynamic closing or opening of individual traffic lanes as warranted and providing advance warning of the closure(s), typically through dynamic lane control signs, to safely merge traffic into adjoining lanes. Often installed in conjunction with DSPL, and also supports the ATM strategies of DShL and DJC.	Incident management; shoulder use; reversible lanes; managed lanes	Some or all lanes on a facility; bridges; tunnels
DShL (Dynamic Shoulder Lane) Part-time shoulder use; hard shoulder running; bus-on-shoulder; dynamic shoulder lanes	The dynamic enabling of the use of the shoulder as a travel lane(s) based on congestion levels during peak periods and in response to incidents or other conditions as warranted during nonpeak periods. May be restricted to certain types of vehicles or occupants. This strategy is frequently implemented in conjunction with DSpL and DLA. Static, time-of-day approaches are not generally included in the definition.	Recurring congestion; incident management; managed lanes (occupancy-based or vehicle-based)	Any facility with available shoulders
QW (Queue Warning)	The real-time display of warning messages (typically on dynamic message signs and possibly coupled with flashing lights) along a roadway to alert motorists that queues or significant slowdowns are ahead, thus reducing rear-end crashes and improving safety. QW may be included as part of DSpL and DLA strategies. Static QW signs are not included in this definition.	Recurring congestion; incident management; WZs	Spot specific, in advance of known problem areas
DSpL (Dynamic Speed Limit) Variable speed limit; speed harmonization	The adjustment of speed limit displays based on real-time traffic, roadway, and/or weather conditions. Can either be enforceable (regulatory) speed limits or recommended speed advisories and can be applied to an entire roadway segment or individual lanes. This "smoothing" process helps minimize the differences between the lowest and highest vehicle speeds.	Recurring congestion; weather; incident management; WZs	Spot specific; facility
Dynamic Merge Control (DMC) Dynamic late merge; dynamic early merge	The dynamic management of the entry of vehicles into merge areas with a series of advisory messages approaching the merge point that prepare motorists for an upcoming merge and encouraging or directing a consistent merging behavior. Applied conditionally during congested (or near congested) conditions, such as a work zone, it can help create or maintain safe merging gaps and reduce shockwaves upstream of merge points.	Recurring congestion; WZs	Limited-access facilities; arterials; spot specific

Adaptive Ramp Metering (ARM)

ARM, which is applicable on limited-access facilities, is the deployment of traffic signals on ramps to dynamically control the rate at which vehicles enter a freeway facility. It utilizes traffic-responsive or adaptive algorithms (as opposed to pretimed or fixed-time rates) that can optimize either local or system-wide conditions. A variation of ARM is bypass lanes on freeway ramps. Some potential benefits of this operational strategy include:

• Delayed onset of mainline breakdown.
• Reduced mainline travel delay.
• Improved travel time reliability.
• Reduced ramp delay as freeway demands subside.
• Reduced vehicle hours traveled.
• Reduced crash rates.

For more information on ARM, visit the FHWA Ramp Metering website (https://ops.fhwa.dot.gov/freewaymgmt/ramp_metering/index.htm).

Table 3 provides a list of recent ARM applications in the United States. They represent some recent deployments that work to address broad mobility challenges in their respective regions. ARM is readily compatible with other ATM strategies, including DJC, ATSC, DLR, and dynamic shoulder use.

Table 3. ARM example applications.

ARM Application	Project Description	Lead Agency
Real-Time Adaptive Ramp Metering, I—680 (2011)	The ramp metering plan for southbound I-680 uses a real-time adaptive system that monitors traffic volumes and density and adjusts the ramp metering rate based on thresholds that vary by time of day set for the travel demand at each ramp.	California DOT (Caltrans)
Congestion Relief Project, I-210 (2009)	The main objective of the I-210 Congestion Relief Project is to better regulate the flow of vehicles entering the freeway system. Advanced metering equipment and algorithms are used with on-ramp meters, freeway-to-freeway connector meters, and HOV bypass lane metering as part of the deployment along a 50-mi corridor, both eastbound and westbound on I-210.(14)	Caltrans

As with traditional ramp metering, agencies may face challenges with implementing ARM within their jurisdictions. These challenges may include existing ramp geometry, heavy ramp volumes that may create queuing issues, public and/or local agency opposition, and lack of agency support.⁽¹⁵⁾ Nonetheless, agencies can take a variety of approaches to mitigate these challenges and successfully implement ARM. A photograph of a ramp meter deployed in Texas is shown in Figure 5.

Figure 5. Photo. Adaptive ramp metering on I-45, Houston, TX (Source: TTI).

Adaptive Traffic Signal Control/Preferential Multimodal Control (ATSC)

ATSC is the continuous monitoring of arterial traffic conditions and queuing at intersections and the dynamic adjustment of signal timing to smooth traffic flow along coordinated routes and to optimize one or more operational objectives (such as minimize overall stops and delays or maximize green bands). Applicable on arterials, this strategy is also known as responsive and/or multimodal preferential signal control. Variations of this strategy include dynamic signal re-timing, queue jump, specialized signal timing plans, and transit signal priority. Some potential benefits of this operational strategy include:

• Reduced arterial travel time.
• Reduced arterial travel delay.
• Improved arterial travel time reliability.
• Reduced number of stops.
• Reduced intersection delay.
• Reduced queue lengths.
• Increased arterial speeds.

Table 4 provides a list of recent or pending ATSC applications in the United States. ATSC is readily compatible with adaptive ramp metering and DLUC.

Table 4. ATSC example applications.

ATSC Application	Project Description	Lead Agency
ATSC for McKnight Road Corridor, Allegheny County, PA (2014)	Deployment involved the introduction of ATSC to the McKnight Road (SR4003) corridor in Pennsylvania between I-279 and Perrymont Road/Babcock Boulevard in Allegheny County. It focused on evaluating and deploying ATSC, connecting traffic signals back to the PennDOT regional traffic management center, deploying and evaluating real-time traffic signal performance metrics along the corridor, and deploying dedicated short-range communications (DSRC) technology in the corridor to facilitate connected and automated vehicle research.(16)	Pennsylvania DOT (PennDOT)
Adaptive Signal Control (2015)	Project included installation of adaptive signal control (ASC) controllers and associated technology at eight signalized intersections along four-lane arterial state roadway adjacent to the airport. The project is the first deployment of ASC in Rhode Island.(17)	Rhode Island Airport Corporation
Midtown in Motion (2011)	Deployment included 100 microwave sensors, 32 traffic video cameras, and E-Z Pass readers at 23 intersections to measure traffic volumes and congestion and record vehicle travel times. The combined data are transmitted wirelessly to the city's TMC in Long Island City, allowing engineers to quickly identify congestion choke points as they occur and remotely adjust Midtown traffic signal patterns to clear traffic jams.(18)	New York, NY

ATSC is not without its challenges. For example, agencies need to ensure that any ATSC system can be integrated with legacy systems in place. Operators need to be able to transition between existing systems and the ATSC system easily, and this can be facilitated with a friendly user interface and an effective configuration tool.⁽¹⁹⁾ Additionally, if compatible ATM strategies such as ARM are in operation in a corridor, coordination between the two strategies is essential to ensure efficient operation. A screenshot of the ATSC application deployed in New York City is shown in Figure 6. A photograph of the video wall from the New York City traffic management center showing camera feeds from instrumented intersections is shown in Figure 7.

For more information on ATSC, visit the FHWA Traffic Signal Timing & Operations Strategies website at (https://ops.fhwa.dot.gov/arterial_mgmt/tst_ops.htm) and Adaptive Signal Control Technology website (https://www.fhwa.dot.gov/innovation/everydaycounts/edc-1/asct.cfm).

Figure 6. Graphic. ATSC application in New York City (Source: New York City Department of Transportation).

Figure 7. Photo. ATSC camera images in New York City (Source: New York City Department of Transportation).

Dynamic Junction Control (DJC)

DJC is the dynamic allocation of lane access on mainline and ramp lanes in interchange areas with high traffic volumes, and where the relative demand on the mainline and ramps changes throughout the day. Through the use of signs, mainline lanes can be closed or become an exit, shoulders can be opened, and so forth to accommodate entering or exiting traffic. A strategy variation is dynamic turn restrictions on arterials. DJC is applicable to interchanges and on/off ramps. Table 5 provides a list of recent DJC applications in the United States. Some potential benefits of DJC include:

• Reduced travel time.
• Reduced travel delay.
• Reduced ramp delay.
• Increased travel speeds.

Table 5. Dynamic junction control example applications.

DJC Application	Project Description	Lead Agency
Dynamic Lanes on SR 110 (Pasadena Freeway) (2012)	Uses junction control to provide a connector lane during peak hours to I-5 northbound.(20)	Caltrans
SR 520/I-90/I-5—Active Traffic Management (2010)	Employs DJC using lane control signs. During times with heavy ramp volumes, traffic is advised to move over from the rightmost lane to reduce conflicts in the merge area.(21)	WSDOT

The deployment of DJC in Los Angeles (see Figure 8) involved opening the right shoulder on the connector ramp during the peak period to provide additional capacity to improve safety and mobility on the connector to eliminate the occurrence of drivers traveling on the shoulder of the connector during peak periods. When the junction control was active and the ramp shoulder was open, a DMS over the shoulder indicated that it was available for use as an exit lane, and a diagrammatic sign was illuminated over the second-from-the-inside lane to indicate that it could be used as a through lane or for the left exit to I-5. DJC is readily compatible with ARM, DLUC, DLR, and dynamic shoulder use.

For more DJC information, visit the Texas Mobility Investment Priorities website at (https://mobility.tamu.edu/mip/strategies-pdfs/active-traffic/technical-summary/Dynamic-Merge-Control-4-Pg.pdf). Note, the application is termed dynamic merge control on this site.

Figure 8. Photo. Dynamic junction control signing on SR 110 (Pasadena Freeway), Los Angeles, California (Source: Caltrans).

Agencies considering DJC to mitigate congestion of bottlenecks need to ensure the location will support the strategy. Factors that support DJC include large variations in mainline and ramp volumes and the ability to use a mainline lane or shoulder to accommodate ramp traffic.⁽¹³⁾

Dynamic Lane Reversal (DLR)

DLR is the reversal of one or all lanes to dynamically allocate capacity of congested roads, allowing capacity to better match traffic demand throughout the day. Lane reversal could include changing the number of available lanes per direction by physically moving barriers or by signage. This strategy is also known as reversible lanes, contraflow lanes, and tidal flow, and it is applicable on limited-access facilities and multilane arterials. Some potential benefits of this strategy include:

• Increased throughput during lane reversal operations.
• Decreased travel times.
• Decreased crash rates.
• Improved level of service.

Table 6 provides a summary of recent applications of DLR in the United States. This strategy is readily compatible with DJC, DLUC, and ARM.

Table 6. Dynamic lane reversal example applications.⁽²²⁾

DLU Application	Project Description	Lead Agency
I-15 Express Lanes, San Diego (2002)	The 20-mi facility between SR 163 and SR 78 features four lanes with a movable barrier for optimal flexibility and capacity allocation. It provides multiple access points to the general-purpose lanes as well as direct access ramps for bus rapid transit service.	Caltrans
Reversible Lane Operation on Arterial Roadways, Washington, DC (2001)	The reversible lanes are implemented with and without dynamic signage to improve traffic flow during rush hours in corridors that predominately accommodate commuter traffic and have a distinct imbalance in directional traffic. They are also used on an ad-hoc basis for emergency evaluations, traffic maintenance in work zones, and special events.	District of Columbia DOT and Montgomery County, MD
Reversible Lanes, Arlington, TX (2009)	The city constructed a reversible lane system on two major and one minor arterial road used for event traffic at The Ballpark in Arlington and the new Dallas Cowboys Stadium at a cost of $3 million. The system utilizes signage and dynamic overhead lane control signs.	City of Arlington

A freeway application of DLR is shown in Figure 9 along I-30 in Dallas, Texas, east of the downtown area. In this installation, a movable barrier is used to provide a dedicated, barrier-separated HOV lane in the peak-period direction. The lane forms its own corridor within the freeway, and access is limited at only a few selected locations.

For more DLR applications related to managed lanes, visit National Cooperative Highway Research Program (NCHRP) Report 835 (http://www.trb.org/main/blurbs/175082.aspx).

Figure 9. Photo. Dynamic reversible lane on I-30, Dallas, Texas (Source: TTI).

Typical lane reversal strategies on freeways include increasing capacity in a peak direction, providing for emergency operations (contraflow lanes), or incorporating lanes as part of a managed lane facility such as a high occupancy toll or HOV lane. On arterials, lane reversals account for directional traffic flows. The ability to reverse lanes might be an important element of traffic management response during emergencies.

DLR applications can be challenging to implement. When reversing direction, agencies need to ensure that the facility is clear so that head-on collisions do not occur. Furthermore, signing to indicate directional reversal needs to be prominently displayed and clearly understood by system users. Additionally, capacity at each end of the reversal needs to be maintained to reduce the likelihood of bottlenecks.⁽¹³⁾

Dynamic Lane Use Control (DLUC)

DLUC is the dynamic closing or opening of individual traffic lanes as warranted and providing advance warning of the closure(s), typically through dynamic lane control signs, to safely merge traffic into adjoining lanes. It is often installed in conjunction with DSpL and also supports the ATM strategies of DShL and DJC. Dynamic lane assignment (DLA) is another term frequently used for this strategy, particularly on arterial facilities. Some potential benefits of this strategy include:

• Increased capacity when used with dynamic shoulder use.
• Increased lane-level volumes.
• Reduced secondary accidents.
• Compliance with posted signage during different flow conditions.
• Improved responder safety.

Table 7 provides information on two DLUC applications in use in the United States. This strategy is readily compatible with DJC, DLR, QW, dynamic shoulder use, and DSpL. DLUC can be applied to all lanes on a facility, specific lanes on a facility, or bridges and tunnels.

Table 7. Dynamic lane use control example applications.

DLUC Application	Project Description	Lead Agency
Virginia—I-66 ATM Project (1992/2015)	The segment of I-66 between U.S. 50 and I-495, where the case study HOV/shoulder lane combination is operational, includes three main lanes in each direction. The shoulder was opened to peak-period, peak-direction general-purpose traffic, allowing the leftmost lane to operate as an HOV lane. The most recent evolution of ATM that is now operational includes variable speed limits, dynamic lane control, and QW as part of an ATM deployment project.(23)	VDOT
SR 520/I-90/I-5—Active Traffic Management (2010)	The signs post variable speed limits and lane status information that helps to warn drivers of backups ahead and smooth out traffic as it approaches a lane-blocking incident. The overhead signs can also quickly close entire lanes and provide warning information to drivers before they reach slower traffic.(21)	WSDOT

Similar to DLR and DJC, information delivery related to the presence and operational status of DLUC is important. Clear, unambiguous lane control signage ensures system users know which lanes are open for travel and when they must vacate a lane that is closing. The VDOT application of DLUC is shown in Figure 10.

For more information related to motorist understanding of DLUC, visit (https://www.fhwa.dot.gov/publications/research/safety/16037/002.cfm).

Figure 10. Photo. DLUC application on I-30 in Texas (Source: TTI).

Dynamic Shoulder Lane (DShL)

DShL is the dynamic enabling of the use of the shoulder as a travel lane(s) based on congestion levels during peak periods and in response to incidents or other conditions as warranted during nonpeak periods. Use of the shoulder may be restricted to certain types of vehicles or occupants. This strategy is frequently implemented in conjunction with DSpL and DLA. Static, time-of-day approaches are not generally included in the definition. DShL is also known as part-time shoulder use, hard shoulder running, bus-on-shoulder, and dynamic shoulder use, depending on the particular application. Some potential benefits of this strategy include:

• Improved level of service when shoulders are in operation.
• Reduced travel time.
• Increased travel time reliability.
• Reduced crash rates.
• Reduced crash severity.

For more DShL information, see FHWA's guide on use of freeway shoulders for travel (https://ops.fhwa.dot.gov/publications/fhwahop15023/).

Recent applications of DShL are provided in Table 8. This strategy is readily compatible with DJC, DSpL, ARM, DLUC, and QW. FHWA released a guide for planning, evaluating, and designing part-time shoulder use in 2016, which covers a wide variety of design and operational concepts for shoulder use and a process for planning for shoulder use on facilities.⁽²⁴⁾

Table 8. Recent DShL example applications.

DShL Application	Project Description	Lead Agency
Virginia—I-66 ATM Project (1992/2015)	The segment of I-66 between U.S. 50 and I-495, where the case study HOV/shoulder lane combination is operational, includes three lanes in each direction. Starting in 1992, the shoulder was opened to peak-period, peak-direction general-purpose traffic, allowing the leftmost lane to operate as an HOV lane. The most recent evolution that is now operational includes variable speed limits, dynamic lane control, and QW as part of an ATM deployment project.(23)	VDOT
Priced Dynamic Shoulder Lane on I-35W (2009)	The I-35W ATM installation includes several strategies aimed at improving safety and congestion (both recurrent and nonrecurrent). One of the core strategies is a priced DShL heading into Downtown Minneapolis.(25)	Minnesota DOT (MnDOT)

Public concerns regarding safety of the lanes need to be addressed as part of the deployment. Depending on the location, there might be concern that the use of shoulder lanes for general traffic will make the traffic conditions worse by attracting more traffic to the facility. Noise concerns also need to be addressed, and the shoulder needs to be able to handle regular use either as is or with rehabilitation. Law enforcement should also be engaged early in the planning process and pushed toward being champions of shoulder use for travel. The WSDOT application of DShL is shown in Figure 11.

Figure 11. Photo. DShL application in Seattle, Washington (Source: WSDOT).

Queue Warning (QW)

QW is the real-time display of warning messages (typically on dynamic message signs and possibly coupled with flashing lights) along a roadway to alert motorists that queues or significant slowdowns are ahead, thus reducing rear-end crashes and improving safety. QW may be included as part of DSpL and DLA strategies. Static QW signs are not included in this definition. This strategy is typically applied in specific locations in advance of known congestion points. Some potential benefits of this strategy include:

• Reduced rear-end crashes where the warning is in effect.
• Increased travel speeds.
• Reduced speed differential.

Table 9 provides some recent examples of QW implementation in the United States. This strategy is readily compatible with DLUC, dynamic speed limit, DJC, and dynamic shoulder use. Figure 12 shows the DMS displaying a QW message as part of a work zone deployment along I-35 in Waco, Texas. Figure 13 shows the QW displays in Minneapolis.

For more QW information, visit the Texas Mobility Investment Priorities website (https://mobility.tamu.edu/mip/strategies-pdfs/active-traffic/technical-summary/Queue-Warning-4-Pg.pdf).

Table 9. Queue warning example applications.

QW Application	Project Description	Lead Agency
Work zone end-of-queue warning system on I-35 (2012)	The project's main purpose is to let motorists know they are approaching a queue of stopped or slowed vehicles as they approach a work zone on I-35. Slowed traffic sometimes occurs during construction, particularly when lanes are closed to accommodate work crews.(26)	Texas Department of Transportation
ATM system on OR-217 (2013)	The project uses speed advisories, QW, and travel times on OR-217 for congestion mitigation and road weather management.	Oregon DOT (ODOT)

QW systems present challenges when placed in the vicinity of rapidly fluctuating queues. If the signs or devices are not located appropriately, the queue tails might be overrun and drivers could encounter the queue before they see the sign. Alternatively, the warning signs might be placed too far from the end of the queue, and drivers will pass the sign long before encountering the queue. Regular monitoring of queue lengths downstream of these installations is needed to ensure they are located properly. Additionally, an automated system for real-time adjustments to locate queues is optimal when conditions quickly change.

Figure 12. Photo. Queue warning work zone application on I-35, Waco, Texas (Source: TTI).

Figure 13. Photo. Queue warning message boards on I-94, Minneapolis, Minnesota (Source, MnDOT).

Dynamic Speed Limits (DSpL)

DSpL involves the adjustment of speed limit displays based on real-time traffic, roadway, and/or weather conditions. Speeds can either be enforceable (regulatory) speed limits or recommended speed advisories and can be applied to an entire roadway segment or individual lanes. This smoothing process helps minimize the differences between the lowest and highest vehicle speeds. Other terms commonly associated with DSpL include variable speed limits and speed harmonization. Some potential benefits include:

• Reduced difference between posted speed versus actual speed.
• Reduced speed variability.
• Reduced spatial extent of congestion.
• Reduced temporal extent of congestion.
• Reduced crash rates.
• Reduced crash severity.

For more DSpL information, visit FHWA's Synthesis of Variable Speed Limit Signs (https://ops.fhwa.dot.gov/publications/fhwahop17003/fhwahop17003.pdf).

Several applications of DSpL are presented in Table 10. This strategy is readily compatible with dynamic shoulder use, QW, and DLUC.

Table 10. Dynamic speed limit example applications.

DSpL Application	Project Description	Lead Agency
Variable Speed Limit on I-95 and I-295 (2008)	The regulatory speed limit is lowered based on road conditions and travel speeds. Specific weather variables that are monitored include precipitation types and amounts, speed drops of more than 20 mph, and other incidents that can cause a change in the VSL.	Maine DOT
Variable Speed Limit System on the PA 76 Toll Road, between MP 162 to MP 172 (2005)	The Turnpike Commission adjusts the regulatory speed limit based on visibility. Speed limits are related to visibility levels based on the stopping sight distances taken from the American Association of State and Highway Transportation Officials (AASHTO) Policy of Geometric Design of Highway and Streets. The Road Weather Information System (RWIS) determines visibility in fog-prone areas.	Pennsylvania Turnpike Commission
Variable Speed Limit on I-80 (2010)	WYDOT has installed 28 variable speed limit signs along a 52-mi stretch on I-80 in hopes of reducing winter driving incidents. Engineers have the ability to lower the posted regulatory speed depending on the road conditions.	WYDOT

A Texas Department of Transportation (TxDOT) application of DSpL along Loop 1604 in San Antonio, Texas, deployed as part of a pilot project, is shown in Figure 14.

Figure 14. Photo. Pilot DSpL application in Texas (Source: TTI).

FHWA has released a synthesis of variable speed limit signs that provides a review of current practices, experiences with deployments of DSpL in the United States, and various aspects of practices that can benefit agencies.⁽²⁷⁾

Dynamic Merge Control (DMC)

DMC is the dynamic management of the entry of vehicles into merge areas with a series of advisory messages approaching the merge point that prepare motorists for an upcoming merge and encourage or direct a consistent merging behavior. This strategy is applied conditionally during congested (or near congested) conditions, such as at work zones, and can help create or maintain safe merging gaps and reduce shockwaves upstream of merge points. The strategy is also commonly known as a dynamic late merge or a dynamic early merge. Some potential benefits of the strategy include:

• Reduced rear-end crashes where the merge is in effect.
• Increased travel speeds.
• Reduced speed differential.
• Reduced delay.

For more information on dynamic merge control in a work zone context, visit the National Work Zone Safety Information Clearinghouse (https://www.workzonesafety.org/training-resources/fhwa_wz_grant/atssa_dynamic_lane_merging/).

DMC is a variation of DJC, most frequently applied in work zones. It is readily compatible with ARM, DLUC, DLR, dynamic shoulder use, and QW. An example of DMC from a work zone in Texas is shown in Figure 15 and Figure 16.

Figure 15. Photo. DMC application in Texas, phase 1 (Source: TTI).

Figure 16. Photo. DMC application in Texas, phase 2 (Source: TTI).

1.3 ATDM, ATM, AND TSMO

As discussed previously, ATM is one of three approaches, along with active demand management (ADM) and active parking management (APM), that makes up the broader operations concept of ATDM. ATDM, as defined by FHWA, is the dynamic management, control, and influence of travel demand, traffic demand, and traffic flow of transportation facilities. Through the use of available tools and assets, traffic flow is managed and traveler behavior is influenced in real time to achieve operational objectives, such as preventing or delaying breakdown conditions, improving safety, promoting sustainable travel modes, reducing emissions, or maximizing system efficiency. Through ATDM, agencies and regions attain the capability to monitor, control, and influence travel, traffic, and facility demand of the entire transportation system and over a traveler's entire trip chain. This notion of dynamically managing across the trip chain is the ultimate vision of ATDM.⁽²⁸⁾ This ultimate vision is conceptualized by the active management cycle shown in Figure 17. With active management, agencies continually monitor a particular system and use that information to assess system performance. Performance benchmarks are then evaluated and dynamic actions are recommended to improve performance. Once the selected dynamic actions are implemented, the agency continues monitoring to determine the impacts of those actions, assesses performance, and modifies actions accordingly.⁽²⁸⁾ ATM includes the strategies that focus on the traffic once it enters the transportation network.

ATDM focuses on the ultimate vision of dynamically managing across the trip chain and is conceptualized by the active management cycle.

Figure 17. Graphic. The Active Management cycle.⁽²⁸⁾

ATDM—and by association ATM—is part of the broader concept of TSMO. TSMO is more than a group of strategies or technologies; it is founded on the guiding principles of managing and operating the transportation system in an integrated, active, and performance-driven manner. ATDM focuses specifically on the active management principle of TSMO.

TSMO includes strategies that are dynamic, predictive, proactive, performance driven, continuously monitored, and supply and demand oriented. These types of strategies also describe ATDM and ATM, making them the active piece of the TSMO puzzle. Thus, the implementation of ATM strategies within the TSMO context presents agencies with an opportunity to progress from static operations toward fully dynamic and proactive operation and management of transportation systems.

1.4 SYSTEMS ENGINEERING

Systems engineering is an essential component in the development of an ATM project. Implementing ATM often requires adopting new supporting operating systems or making substantial modifications to existing software platforms and systems. A systems engineering analysis will help to outline key system considerations, identify connectivity needs, and detail system technology options and alternatives. It is also a required component for an ATM project that is using Federal funds, per 23 CFR 940.⁽²⁹⁾

The Vee diagram is widely adopted as the standard for representing the systems engineering process for intelligent transportation system (ITS) projects. Figure 18 shows the process in the context of the transportation/ITS technology planning and implementation life cycle. The FHWA California Division and Caltrans developed the Systems Engineering Guidebook for Intelligent Transportation Systems, Version 3.0,⁽³⁰⁾ which outlines the process from start to finish. Although developed in California, it is applicable for any State or regional agency developing transportation technology projects. The California guidebook developed the Vee diagram shown in Figure 18 to show up-front planning activities, including concept exploration, systems engineering management plan development, and regional ITS architecture development as a foundational element in the process. The right side of the diagram shows increasing levels of detail in the planning, beginning with exploring the concept for ATM, developing a Concept of Operations (ConOps), and moving through more detailed definition tasks of requirements, design, and implementation.

System engineering is an essential component in ATM project development, and the Vee diagram can be readily adopted to ATM projects and meet Federal requirements.

Systems engineering is more than a requirement. The intent of using the systems engineering process to develop transportation technology projects is to reduce risk, verify functionality at key steps, document key project decisions, and get stakeholder consensus at strategic points in the process. The left side of the Vee diagram primarily represents key planning activities: these steps identify needs and problems that need to be fixed, consider different concepts and alternatives, and get input and feedback from a variety of stakeholders (users) on priorities and issues.

Figure 18. Diagram. Systems engineering Vee diagram and the system life cycle.⁽³⁰⁾

ATM Application: When using the systems engineering process for an ATM project, an agency will need to incorporate specific ATM elements into various documents developed as part of the project. For example, WSDOT incorporates specific ATM information in its design requirements for ITS projects. In addition to general information related to VMS, WSDOT includes detailed requirements for VMS at ATM sites, including: Specific installation locations to support dynamic operations for ATM strategies. Unique sign spacing requirements for ATM applications. Placement of ATM-related VMS in relation to exit ramps and on-ramp merge areas. The use and specifications for lane control signals to communicate lane-specific traffic control information associated with ATM strategies. The use, placement, specifications, and appropriate messages for side-mounted signs. Use of full-size and small VMS along with specifications, placement, appropriate message, and co-location with and placement with lane control signals. Intelligent Transportation Systems Design Requirements, 2016, WSDOT, http://www.wsdot.wa.gov/NR/rdonlyres/1C4C6252-17AD-429B-98BA-265E06926B3B/0/Designrequirements.pdf.

At some stage of the planning, the need is identified for a specific ATM project; this is where agency project development and programming processes would integrate the identified ATM project into a transportation improvement plan (TIP), statewide transportation improvement program (STIP), congestion management program, or related effort where an ATM project is assigned funds and a programming year. In other cases, agencies might opt to implement ATM projects with available or discretionary funds without including an ATM project in a TIP/STIP. The cost and complexity of ATM would necessitate inclusion in a more formal TIP or STIP document, or in some cases, a longer-range planning document. The ability to incorporate ATM projects in to the TIP and STIP help these projects compete on a level playing field with more traditional capacity improvements and emphasize the agency culture committed to ATM.

1.5 CHAPTERS AT A GLANCE

This Guide is divided into six chapters. The titles of each chapter and the major topics covered are highlighted below.

• Chapter 1—Introduction. An overview of the document, an introduction to ATM and its context within the overall transportation framework, and a quick guide to the topics covered in the individual chapters are provided in this chapter.
• Chapter 2—Planning and Organizational Considerations. This chapter provides a discussion on the aspects of an agency's approach to planning and developing policy to support ATM.
• Chapter 3—Design Considerations. This chapter reviews the design features and processes that agencies need to consider when moving forward with ATM projects.
• Chapter 4—Implementation and Deployment. This chapter describes the approach to implementing and deploying ATM strategies in a region, including legal issues, stakeholder engagement, and public outreach and involvement.
• Chapter 5—Operations and Maintenance. This chapter provides a narrative on operations and maintenance issues agencies will face once ATM strategies go online.
• Chapter 6—Summary. This chapter reviews the guidance document and emphasizes its goals, objectives, and intended audience, as well as the importance of ATM in supporting TSMO and congestion management.

A list of all references cited within the chapters is included at the end of the document.

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