The Active Transportation and Demand Management Program (ATDM): Lessons Learned
In response to the growing pressure for agencies to do more with less and address congestion challenges from all aspects of the network, the Federal Highway Administration (FHWA) is working to promote a dynamic approach to manage the transportation network. The approach seeks to optimize performance and increase efficiency throughout the entire trip chain as seen from the traveler’s perspective. Termed Active Transportation and Demand Management (ATDM), the program advances the ability to manage, control, and influence travel demand, traffic demand, and traffic flow of transportation facilities.
The program builds off the existing investments that state and local agencies have made in transportation systems management and operations. Investments on our transportation facilities are wide-ranging and include monitoring systems (detectors), communication backbones, advisory systems (message signs, highway advisory radios), field personnel and vehicles (safety service patrols), centers (traffic management centers), public information portals (websites, 511), control systems (traffic signal systems, ramp meters, road/lane closure systems), and operational information exchanges (Computer Aided Dispatch [CAD] integration, data warehousing). Leveraging these investments to realize a greater degree of real-time, dynamic management and operational capability is the primary goal of the program.
As the popularity of ATDM approaches rises across the nation, it is important that agencies understand the impacts and the lessons learned so that they can begin utilizing similar approaches to help create smart transportation infrastructure and programs that are effective in their region for proactively and dynamically managing demand and operations. This document provides insight into lessons learned by early adopters of ATDM in the United States to help provide guidance for agencies considering ATDM for their region.
1.1 The ATDM Operational Concept
ATDM is the proactive and dynamic management, control, and influence of travel demand, traffic demand, and traffic flow of transportation facilities. Under an ATDM approach, the transportation system performance is continuously assessed; dynamic actions using existing tools and assets are constantly evaluated and implemented in real time to achieve performance objectives, such as preventing or delaying breakdown conditions, improving safety, promoting sustainable travel modes, reducing emissions, or maximizing system efficiency. Implemented actions are continuously monitored as they start to affect system performance. This cyclical approach can be carried out at various operational time-scales, ranging from longer-term strategic approaches to the short-term tactical decisions. The general phases of the ATDM approach are illustrated in Figure 1. (1)
As agencies move toward more active management, new and emerging implementation approaches allow for more dynamic operations by agencies leading to more fluid traveler behavior choices to positively affect the system. Broadly, these approaches can be classified into three categories:
- Active Traffic Management: A suite of strategies that actively manage traffic on a facility. Examples include variable speed limits, dynamic shoulder use, queue warning and lane control strategies.
- Active Demand Management: A suite of strategies intended to reduce or redistribute travel demand to alternate modes or routes. Examples include comparative multi-modal travel times, dynamic ride-sharing, pricing and incentive approaches.
- Active Parking Management: A suite of strategies designed to affect the demand, distribution, availability, and management of parking. Examples include dynamic parking pricing, real-time parking availability and reservation systems
An agency can deploy a single ATDM approach in order to capitalize on a specific benefit or can deploy multiple active strategies to gain additional benefits across the entire transportation system. All agencies and entities operating transportation systems can advance toward a more active management philosophy by making changes that move operations along the active management continuum. This progression on the continuum represents a natural evolution in an agency’s ability to provide and the public’s acceptance of active management as shows in Figure 2.
ATDM builds upon existing capabilities, assets, and programs and enables agencies to leverage existing investments—creating a more efficient and effective system and extending the service life of existing capital investments. While active management can be applied to any part of our transportation system (such as implementing dynamic pricing on a facility to manage congestion or informing travelers of specific or compatible transit operations for their trip), it is most beneficial when the relationships and synergies to other parts of the system are considered.
1.2 The International Influence
The origins and the evolution of active management concepts in Europe have considerably influenced the evolving ATDM program in the United States. The antecedents of the ATDM program in the United States emerged from international experience with active traffic management on key highways as well as observing how travel demand management and traffic management are more closely integrated in some other countries. For example, in 1995, the UK Highways Agency in England began to actively manage traffic via variable speed limits. In 2002, full active traffic management (ATM) was installed on the M42 near Birmingham. This project has become the most widely cited example of ATM. The focus of ATM is to reduce bottlenecks and traffic perturbations by utilizing hard shoulder running during peak flows, ramp metering, variable speed limits, and dynamic lane control; detecting and clearing incidents quickly; and improving real-time traffic information.
ATM planners in Europe and elsewhere now use a diverse and flexible set of tools to manage their facilities. Commonly used strategies now include variable speed limits, hard shoulder running, dynamic merge control, adaptive ramp metering, and queue warning and dynamic traveler information. The benefits of these ATM strategies, especially variable speed limits, have been reported to include compliant driver behavior, improved vehicle throughput, travel time reliability, improved safety (especially during inclement weather), and reduced emissions. A 3-year safety review of M-42 highlighted a reduction in the number and severity of personal injury crashes when the ATM operational regimes were in effect. (2)
The ATDM program in the United States emerged from international experience with active traffic management on key highways and how travel demand management and traffic management are more closely integrated in some other countries.
As ATM tools continue to be applied in Europe, both the Dutch Ministry for Transport and the UK Department of Transport recognized that ATM addresses only part of the congestion problem and that there is a parallel and complementary need to manage the demand on the transportation system. The Dutch model of travel demand and traffic management involves a three-stage process that recognizes the difference between travel demand management and traffic management and places these concepts into a larger framework of travel choices and congestion-reduction techniques. As shown in Figure 3, the process begins with the consideration of overall travel demand (the need to travel) and moves through traffic demand (the demand on the transportation system) and network demand (the demand on the individual facilities). Through both traffic and travel demand management strategies, the framework shows how travelers can be provided choices across mode, destination, route, and time.
These international experiences have provided the impetus for the development of an ATDM program in the U.S., drawing from the three technical exchanges between U.S. and European transportation professionals in 2005, 2006, and 2011. The ATDM program has been adapted to meet the needs of the stakeholders in the U.S. Table 1 highlights the key influences from Europe and how they shape the ATDM program in the U.S.
|Influences from Europe||Adaptation to the U.S. Environment||Key Thrusts of the ATDM Program|
Active management as a tactical philosophy
Through the international scans, the value of being more proactive and dynamic in overall operations was noted. Current operations in the U.S. can benefit from such a shift.
Focus on increasing U.S. operating agency's capability to actively manage their facilities, maximizing the use of data, performance assessment and continuous improvement.
Use of ATM strategies to manage motorways
Many of the ATM strategies are of interest in the U.S. Several have been tried in isolation or as part of pilots here.
Continue to promote adoption of ATM strategies, elaborating on how they can be used in the U.S. environment. Focus on a wide range of tools and a wide range of application settings ranging from spot-specific deployments to synergistic large-scale ATM.
Moving toward a performance- or risk-based approach to design for ATM
ATM strategies need to be adapted to the U.S. environment focusing on the unique challenges faced by agencies in design, operations, maintenance and enforcement.
Specific focus is on how the ATM strategies used in Europe can be adapted to U.S. facilities including appropriate design, operations and maintenance, safety, and institutional considerations. A key aspect of the ATDM program involves the sharing of best practices and the development of guidance and technical support to help agencies evaluate and implement ATM in their regions.
Consideration of TDM strategies as part of traffic operations
Traditional TDM is well established in the U.S. In fact, some areas such as carpooling have a long and storied history in the U.S., more so than in Europe. However, traditional TDM approaches have focused on long-term behavior changes. Examples from Europe point to a more operational use of TDM to influence day-to-day travel behavior via incentives, partnerships and traveler information for a wider variety of applications.
The ATDM program in the U.S. supports the development and adoption of active or dynamic approaches to manage demand, especially for short-term travel behavior modifications.
While traditional TDM will continue to play an important role, the ATDM program is focused on strategies that involve influencing travel choices in an active manner.
1.3 Implementation Approaches
As noted before, the tactics for ATDM can be classified into implementation categories like active demand management, active traffic management or active parking management. Typically, these represent the implementation bundles being considered by agencies as part of the ATDM framework. Several of these approaches have been successfully demonstrated in the United States.
1.3.1 Active Demand Management
Active demand management works to influence travel behavior in real time, going beyond traditional demand management to use information and technology to dynamically manage demand to different routes, modes, and/or times of day.
Active demand management (ADM) works to influence travel behavior in real time and goes beyond traditional travel demand management (TDM) to use information and technology to dynamically manage demand including redistributing travel to less congested times of day or routes, or reducing overall vehicle trips by influencing a mode choice.
ADM seeks to influence more fluid travel choices by users on a day to day or even hour to hour basis. Contrasting with traditional TDM, which seeks long-term behavior changes, ADM supports dynamic trip making behavior enabled by technology and connectivity of the modern age. It is supportive of other active measures by redistributing or reducing overall traffic levels during congested conditions, thus becoming an integral part of an overall management philosophy to actively manage a facility or system. (4)
ADM builds upon the success of traditional TDM programs by using new technologies to inform and influence travel choices, which are not limited to mode choice decisions. As with many TDM efforts, financial levers are important to ADM, either as incentives or disincentives (such as higher tolls for single-occupancy vehicle or peak period travel). Incentives can take various forms:
- Travel time savings (high-occupancy vehicle [HOV]/high-occupancy toll [HOT] lanes)
- Direct financial incentives for avoiding peak hour travel
- Gift certificates through points accumulated by offering rides with dynamic ridesharing vendors
- Shopping information or discounts to encourage changes in departure times during peak periods.
Information technology, especially with the connectivity and the social networking possibilities enabled by smartphones, is now being used to dynamically match en-route travelers with others needing a ride or providing comparative travel times for traffic and transit to induce an en-route mode or route shift after a trip as begun. Based on the results of early dynamic ridesharing pilot projects, program managers identified five critical success factors, which could be applied to many ADM strategies:
- A critical mass of travelers within a defined area
- An appropriate incentive program
- Minimal complexity for the user
- Demonstrated security and privacy
- Stakeholder engagements involving highway operators, transit, employers, and businesses to help ensure that the different needs of these groups are addressed by the ADM applications.
The key to successful ADM projects is an integrated approach to offering a technically sound, user-friendly service, with incentives to make a different travel choice, as well as buy-in by key public and private stakeholders. The overall utilization and effectiveness of many of these approaches are still being tested. (4)
1.3.2 Active Traffic Management
Active traffic management approaches seek to increase throughput and safety using integrated systems with new technology, including the automation of dynamic deployment to optimize performance quickly.
Active traffic management (ATM) is the ability to dynamically manage recurrent and non-recurrent congestion based on prevailing and predicted traffic conditions.
Focusing on trip reliability, it maximizes the effectiveness and efficiency of the facility. ATM approaches seek to increase throughput and safety using integrated systems with new technology, including the automation of dynamic deployment to optimize performance quickly and immediately when operators must deploy operational strategies manually. ATM includes dynamic routing, dynamic junction control, adaptive signal control, and transit signal priority. These approaches can be described as follows:
Adaptive ramp metering: The deployment of traffic signal(s) on ramps to dynamically control the rate at which vehicles enter a freeway facility. This in essence smooths the flow of traffic onto the mainline, allowing efficient use of existing freeway capacity. Adaptive ramp metering utilizes traffic responsive or adaptive algorithms (as opposed to pre-timed or fixed time rates) that can optimize either local or system-wide conditions. Adaptive ramp metering can also utilize advanced metering technologies such as dynamic bottleneck identification, automated incident detection, and integration with adjacent arterial traffic signal operations. In an ATDM approach, real-time and anticipated traffic volumes on the freeway facility will be used to control the rate of vehicles entering the freeway facility. Based on the conditions, the ramp meter rates will be adjusted dynamically.
Adaptive traffic signal control: The continuous monitoring of arterial traffic conditions and the queuing at intersections as well as the dynamic adjustment of the signal timing to optimize one or more operational objectives (such as minimize overall delays). Adaptive traffic signal control approaches typically monitor traffic flows upstream of signalized locations or segments with traffic signals, anticipating volumes and flow rates in advance of reaching the first signal, and then continuously adjusting timing parameters (e.g., phase length, offset, and cycle length) during each cycle to optimize operational objectives.
Dynamic junction control: The dynamic allocation of lane access on mainline and ramp lanes in interchange areas where high traffic volumes are present and the relative demand on the mainline and ramps change throughout the day. For off-ramp locations, this may consist of assigning lanes dynamically either for through movements, shared through-exit movements, or exit-only movements. For on-ramp locations, this may involve a dynamic lane reduction on the mainline upstream of a high-volume entrance ramp, or might involve extended use of a shoulder lane as an acceleration lane for a two-lane entrance ramp that culminates in a lane drop. In an ATDM approach, the volumes on the mainline lanes and ramps are continuously monitored, and lane access is dynamically changed based on the real-time and anticipated conditions.
Dynamic lane reversal or contraflow lane reversal: The reversal of lanes in order to dynamically allocate the capacity of congested roads, thereby allowing capacity to better match traffic demand throughout the day. In an ATDM approach, based on the real-time traffic conditions, the lane directionality is updated quickly and automatically in response to or in advance of anticipated traffic conditions.
Dynamic lane use control: The dynamic closing or opening of individual traffic lanes as warranted and the providing of advance warning of the closure(s) (typically through dynamic lane control signs) in order to safely merge traffic into adjoining lanes. In an ATDM approach, as the network is continuously monitored, real-time incident and congestion data are used to control the lane use ahead of the lane closure(s) and dynamically manage the location to reduce rear-end and other secondary crashes.
Dynamic merge control: Also known as dynamic late merge or dynamic early merge, this strategy consists of dynamically managing the entry of vehicles into merge areas with a series of advisory messages (e.g., displayed on a dynamic message sign [DMS] or lane control sign) 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, dynamic merge control can help create or maintain safe merging gaps and reduce shockwaves upstream of merge points. In an ATDM approach, conditions on the mainline lanes and ramps approaching merge areas are continuously monitored, and the dynamic merge system is activated dynamically based on real-time and anticipated congestion conditions.
Dynamic shoulder lanes: The use of the shoulder as one or more travel lanes, known as hard shoulder running or temporary shoulder use, based on congestion levels during peak periods and in response to incidents or other conditions as warranted during non-peak periods. In contrast to a static time-of-day schedule for using a shoulder lane, an ATDM approach continuously monitors conditions and uses real-time and anticipated congestion levels to determine the need for using a shoulder lane as a regular or special purpose travel lane (e.g., transit only).
Dynamic speed limits: The adjustment of speed limits based on real-time traffic, roadway, and/or weather conditions. Dynamic speed limits can be either enforceable (regulatory) speed limits or recommended speed advisories, and they can be applied to an entire roadway segment or individual lanes. In an ATDM approach, real-time and anticipated traffic conditions are used to adjust the speed limits dynamically to meet an agency’s goals/objectives for safety, mobility, or environmental impacts.
Queue warning: The real-time display of warning messages (typically on DMS 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. In an ATDM approach, as the traffic conditions are monitored continuously, the warning messages are dynamic based on the location and severity of the queues and slowdowns.
Transit signal priority: The management of traffic signals by using sensors or probe vehicle technology to detect when a bus nears a signal controlled intersection, turning the traffic signals to green sooner or extending the green phase, thereby allowing the bus to pass through more quickly. In an ATDM approach, current and predicted traffic congestion, multiagency bus schedule adherence information, and number of passengers affected may all be considered to determine conditionally if, where, and when transit signal priority may be applied.
The two fundamental concepts of ATM are active management of the capacity and direct interaction with drivers to encourage them to make tactical driving decisions (e.g., stopping, slowing down, and changing lanes). The idea is not to simply react to changing conditions but to anticipate them and actively manage the system prior to their occurrence. All agencies and entities operating transportation systems can advance toward a more active management philosophy by making changes that move operations along the active management continuum. This progression on the continuum represents a natural evolution in an agency’s ability to provide and the public’s acceptance of active management.
Agencies can realize numerous benefits with ATM. General operational benefits include:
- A decrease in primary incidents by alerting drivers to congested conditions and promoting more uniform speeds
- A decrease in secondary incidents by alerting drivers to the presence of queues or incidents and proactively managing traffic in and around incidents
- Increased throughput by reducing the delay associated with the number of primary and secondary incidents, reducing speed differential in traffic flow, and reducing the shockwave effects of excessive braking
- Increased overall capacity by adding shoulder use during congested periods when it is needed most
- Overall improvement in speed uniformity during congested periods
- Increased trip reliability by increasing capacity and throughput, reducing incident delay, and improving vehicle throughput
1.3.3 Active Parking Management
Active parking management is the dynamic management of parking facilities in a region to optimize performance and utilization of those facilities while influencing travel behavior at various stages along the trip-making process, i.e., from origin to destination. Dynamically managing parking can affect travel demand by influencing trip timing choices, mode choice, and parking facility choice at the end of the trip. This ATDM approach can also have a positive impact on localized traffic flow by providing real-time parking information to users and ensuring the availability of spaces to reduce circling around parking facilities. The overall goal is to help maximize the nation’s transportation infrastructure investments, reduce congestion, and improve safety. (5)
Active parking management is the dynamic management of regional parking facilities to optimize performance and utilization while influencing travel behavior at various stages along the trip-making process.
A fundamental component of active parking management is information. With clear, detailed, relevant, and real-time parking information, travelers can make informed decisions regarding their trip. The information a user needs to make parking-related decisions can be conveyed in numerous ways and in various formats. These include, but are not limited to, traditional static road signs, dynamic message signs, the Internet, cell phones, smartphones and similar mobile devices, and navigation systems. Agencies can harness the power of an enhanced technology infrastructure (wireless and wired communications, embedded sensors, etc.), combine it with the breadth of currently available technologies to convey information as well as to accept reservations and parking payments, monitor use, and conduct enforcement. These technologies can be applied to both on-street and off-street parking spaces to optimize use of all facilities in a region. (5)
Parking system operators also realize numerous benefits with active parking management. Agencies can reduce costs, improve efficiency, and increase parking utilization rates. By increasing the availability of limited parking spaces and optimizing the use of facilities at all times of the day, agencies can help reduce congestion in and around parking facilities, improve enforcement efficiency, foster public trust, and accommodate alternative payment methods. Active parking management also benefits a region as a whole by reducing pollution, encouraging the use of alternative modes, relieving congestion around commercial businesses, and helping improve access for emergency responders. In some cases, agencies can actually increase parking capacity within a limited footprint with innovative parking facility designs that stack vehicles and/or automate parking.
1.4 The Impact of Strategies on the Trip Chain
ATDM is intended to influence travel behavior throughout the entire trip chain, as shown in Figure 4. The process begins with the consideration of overall travel demand and moves through traffic demand and network demand. Through both traffic and travel demand management strategies, travelers can be provided choices across mode, destination, route, and time. By using the various ATDM approaches at each stage of the trip, agencies can work to influence behavior and the resulting demand on the system to optimize performance.previous | next