AHB20: Committee on Freeway Operations

Chairman: Peter M. Briglia Jr., PSRC

Freeway Operations in 2006 and Beyond

Authors: Members and Friends of the Committee on Freeway Operations

The fundamental purpose of freeway operations,  the reason for being, is to combat congestion and its damaging effects….driver delay, inconvenience and frustration, reduced safety, and poor air quality.  This is no easy task, for congestion is a complex phenomena….a two-headed monster….that not only clogs our freeway systems with stop-and-go traffic, but, at the same time, robs the freeway of its ability to carry traffic.  It is the direct result of an imbalance in the Capacity/Demand relationship—too much demand, too little capacity.  So dealing with congestion must necessarily focus upon ways to manage both the capacity and the demand such that the demand will never exceed the capacity.  And, we are dealing with a moving target, in that both the capacity and the demand are continually changing; thus, this balancing act must be carried out on a real-time basis.

A LOOK AT CONGESTION

If we are to combat congestion, we must first understand congestion….its causes, its dynamic nature, its effects.  It comes in two varieties—recurrent and non-recurrent. Recurrent congestion, associated with the peak period commuter traffic, occurs when demand increases to the point where it overwhelms capacity; it is a case of too many cars, too few lanes.  On the other hand, non-recurrent congestion comes about as the result of losing capacity, typically when lane(s) are blocked by accidents or other occurrences. 

Field observations have revealed that three key events, all linked together, occur as congestion on the freeway sets in….

·        The Break-Down in Traffic Flow.  As traffic demand builds to the point where it approaches the capacity of the freeway, some turbulence in flows takes place, and congestion begins to form.  As more traffic crowds onto the freeway and capacity is overwhelmed, there is a break-down in traffic flows, and heavy congestion, and the inefficiencies inherent in operation under heavy congestion, set in.

·        The Loss in Operational  Efficiency.  Inefficiencies in operation lead to a loss in the ability of the freeway to handle high volumes of traffic, and there is a significant drop in throughput on the freeway.   The system continues to operate in this crippled state until such time as the demand drops to the point where smooth flows are restored. 

·        Driver Behavior.  Drivers make changes in their travel patterns in response to the flow conditions which they encounter.  When they see improved flow conditions, they will shift to take advantage of the improvements, pushing their way onto already crowded freeways, to the point of setting into motion the series of events noted above ….the break-down of traffic, the inefficiencies, the heavy congestion, and prolonging the recovery of the freeway.

This three-step cycle, working in an unmanaged fashion, presents a seemingly hopeless situation…any improvements in flow brought about by congestion relief efforts are, in a relatively short time, overrun by traffic, and congestion reappears. On the other hand, if we can manage these same dynamics through the application of an array of freeway operations measures, and break the cycle, there is at least a ray of hope in the fight against congestion.              

We must take note of the paradox in all of this. The greatest motivation for the motoring public to change travel practices—to divert to alternative routes, to other times, to high-occupancy vehicles, or to transit—is the opportunity to avoid the traffic jams on the freeway.  This point has been used extensively in marketing efforts to encourage the public to make such changes. In fact, experience has shown that in the absence of congestion, the public is not willing to make such changes. Thus, the freeway operator finds that, to the degree that freeway operations programs are successful in eliminating congestion, the public’s incentive to make changes to achieve that success erodes. Such is the nature of the freeway operations program.

A LOOK BACK….WHERE WE HAVE BEEN

In the late 1960s and early 1970s, highway agencies began to take steps toward active operation of the freeways that had been constructed through the golden years of the Interstate Program. Emphases in highway transportation began to shift from building new facilities and enlarging existing ones to extracting the most from existing facilities. It was the dawn of the era of freeway operations and traffic management.

Authorities began to realize that understanding how the public used highways and how operating agencies managed that use was crucial to maintaining operational efficiency. Allowing unrestrained growth in the use of the freeway network produced congestion, which effectively reduced freeway capacity, lowered traveling speeds, and raised blood pressures. Tools that could manage and reduce the congestion plaguing our highways were sorely needed. Researchers used studies of highway usage to come up with the concepts and approaches that have since evolved into freeway traffic management programs. They realized that implementing these programs could cost-effectively influence the public’s use of the highway system.

Agencies, recognizing that different, yet related, approaches were needed to deal with both types of congestion---recurrent and non-recurrent--- began to develop traffic management programs.  Systems were developed and deployed; theories were tested and validated; algorithms were created and refined as new information provided more insight into the problem and into ways to detect it.  For recurrent congestion, measures included surveillance and control systems that featured detection systems, ramp meters, changeable message signs, closed-circuit television cameras, and traffic operations centers.  Dealing with non-recurrent congestion required the same infrastructure, but more personnel involvement: interdisciplinary incident management teams, service patrols, and tow trucks.  Motorist advisory systems worked under both conditions to inform motorists of incidents and flow conditions ahead.  Documented improvements in congestion levels and in highway safety helped to garner support in the early years.

In the early ‘80’s, the concept of managed lanes, in the form of HOV lanes, came upon the scene.  Over the next decade, several demonstration projects were undertaken; a variety of configurations and operating strategies were deployed and tested; fine tuning and adjustments took place; a series of guidelines for geometric layout and operational practices began to evolve.  Strong attitudes, both pro and con, regarding the use of “diamond lanes”, were being voiced.  The general public, elected officials, and operations agency officials took stands and joined the debate over the sensibility, the operational integrity, the safety, and the fairness of this use of highway lanes.  In this atmosphere, the concept took hold and its use grew through the 1990’s.  Its use was further expanded to include HOT lanes and peak-hour pricing schemes.

There was a surge in freeway operations and traffic management during the ‘80’s and ‘90’s as intelligent transportation systems (ITS) burst upon the scene.  The practice of freeway operations had developed to the point where new and better systems in the areas of detection, communications, information gathering, and dissemination were needed.  New technologies had been developed, and more were on the way.  These systems were just what the operations community needed; the joining of the two initiatives was a natural.  And with ITS came greater interest in freeway operations, and increased levels of funding.  There was a flurry of activity as ITS plans across the country were developed and adopted, and deployment of ITS took place.

During this same period of time, the notion of freeway corridor traffic management (FCTM) caught on.  Operators of the freeway system (State DOTs) and the surface street system (local agency DOTs) recognized the benefits of integrating systems and coordinating the operation of the two components. A limited number of corridor traffic management demonstration projects were initiated, the concepts were validated.  Since then, the view of FCTM has been broadened to include not only the freeways and streets, but all transportation facilities and services within the corridor.  There has been greater emphasis placed on planning and operating the transportation system as a whole, rather than as a series of component parts. This has brought with it the need for even higher levels of integration of systems, of coordination of agency activities, more interagency requirements and strengthened working relationships.  More sharing of information is called for; more open communication is a must; the building of trust between agencies is essential.

Over the past three decades, the practice of freeway operations has matured. Strategies have evolved, techniques have been developed, and new technologies have emerged.  We have seen both successes and failures; valuable lessons have been learned.  Each new generation has brought its challenges; each has delivered its benefits.  A sound foundation for moving ahead is in place.

A LOOK AT TODAY…..WHERE WE ARE

Current developments in freeway management systems focus on deploying infrastructure, integrating systems, and expanding the functionality of systems.  During the past few years, the practice of freeway operations/traffic management has settled into the deployment and operation of a somewhat standard package of systems that has evolved from lessons learned over the past 30 years.  The package features the blending of infrastructure, technology, institutional arrangements, working relationships, and operating policies; it consists of surveillance systems, algorithms, ramp metering, operation centers, variable message signs, incident detection and response, and information dissemination.

Yet, in spite of all the advances, of all the lessons learned, of the application of ITS, of the well-documented benefits of traffic management programs, the credibility of freeway management systems continues to be challenged.  Three things are having an effect: first, the public has expressed strong dissatisfaction with traffic management strategies which they perceive as attempts by government to restrict or control their travel; secondly, there is continued resistance on the part of drivers to divert to alternative routes, to delay their travel, to shift to other modes, or to cancel their trips; and finally, there are still the endless traffic jams on our freeway systems.  The prevailing attitude is, “I have the right to drive my car where I want, how I want, and when I want.” 

Clearly, there is more work to be done.

A LOOK AT TOMORROW….WHERE WE NEED TO GO

We need to stay the course—to continue to foster and promote the concepts of traffic management, to expand infrastructure, to develop working relationships, to adopt policies, to disseminate information, to manage incidents.

Overall, there is the need for operations agencies to become more proactive, rather than continue in their traditional reactive role, in their approach to freeway operations/traffic management.  Additionally, there are a host of “needs” that we must address.  Several of those, each calling for greater attention and intensification of our efforts, are listed below.

·        Deployment.  Stepped-up installation of infrastructure on both freeways and surface streets.

·        Interagency Relationships.  To resolve jurisdictional issues associated with the integration of systems and coordination of efforts.

·        Documentation of Successes.  To provide the foundation for management to support continuance, and expansion, of traffic management programs.

·        Development of “Operations Mentality” within operating agencies to create an institutional culture in which traffic management can thrive.

·        Development of incident response plans to define/clarify responsibilities, to establish call-up lists, to shorten response times, all aimed at hastening the return of highway facilities to normal operation.

·        Information dissemination, including the deployment of systems, information sharing, and relationships with the media.

·        Educational programs to establish the credibility of traffic management programs through raising the awareness of the public, of elected officials, and of agency management as to the impacts of driver behavior upon the operation of the freeway, and of the benefits of the application of traffic management measures.

·        Expectations.  Establishment of realistic expectations of performance, matched to achievable levels of improvement, in order to avoid the erroneous perception that the program/project has failed.

·        Coordination.  Intensify efforts to coordinate the interactions of emergency responders (police, fire, medical), as well as incident management players (freeway operators, truckers/shippers, tow truck operators, maintenance crews) at accident scenes.

Additionally, there is a “now” need to take the practice of freeway operations to the next level, to get out ahead of the curve, to develop the capability to predict the onset of congestion before it sets in.  Our use of detection systems and algorithms needs to be focused upon measuring those traffic flow conditions which are present in the traffic stream just before the onset of congestion, those conditions which lead to the formation of congestion.  Then, the freeway operator (and the public) must activate various measures to assure that the  three-step cycle—the break-down in traffic flows, the losses in efficiency, and the shifting of traffic patterns—is never triggered. [In contrast, today’s systems detect conditions which are present after the onset of congestion; at that time, the devastating effects of the three-step cycle have already been set into motion, and there is little the freeway operator can do but wait it out.]

THE CHALLENGES OF TOMORROW

Indeed, the path ahead for freeway operations/traffic management programs is fraught with challenges.  Not surprisingly, the major challenges are not of a technological nature; the technologies to do the job are here and are being used in today’s systems, and advances in technology will only help matters.

The real challenges are those that are people-oriented—those that call upon people to move beyond the attitudes, the issues, the arrangements, and the practices of the past, and to seek better ways of delivering transportation services to the public.  Meeting the challenges will call for changes, many revolutionary in nature, for virtually every segment of the transportation community—providers as well as users.  Thinking “outside of the box” will be essential.

 Several of the most challenging of these are listed below.

·        Credibility.  Establishing and maintaining credibility—with the public, with elected officials, and with agency management—has proved to be particularly troublesome in the past, and there is no reason to believe that it will be any easier in the future.  In fact, it is expected that achieving this will be doubly difficult, given our past record, and the fact that, in spite of all our efforts, there is little-or-no perceivable improvement in levels of congestion on either our freeways or surface streets.  Credibility hinges, to a large degree, upon meeting public expectations, so it is essential that realistic (and achievable) expectations be established, performance on operating projects be documented and fully disclosed, and….communicate, communicate, communicate.

·        Cooperation, Coordination, Integration of Systems.  It is well recognized that if we are to optimize mobility for people and goods within a corridor (and for that matter, within a region), we must treat the transportation system, comprised of a number of different sub-systems, as a whole. And in the area of operations, this will call for full integration of systems, coordination of the provision of services, and the highest degree of cooperation between service providers.  Here again, the importance of good, open communication, with the full sharing of information, cannot be overstated.

·        Mainstreaming Freeway Operations.  It is essential that Freeway Operations be recognized as one of the core functions in which DOTs are engaged, and be given appropriate priority in programming, funding, and staffing processes.  Up-front attention must be given to Operations in the planning, design, and construction phases of freeway programs/projects.

·        Operations Mentality.  Development of an Operations Mentality within transportation agencies is an absolutely essential early step along the path to Mainstreaming Freeway Operations.  This has proven to be a particularly difficult area in which to deal, in that it calls for a change in the long standing, deeply ingrained culture within an organization.  In the case of DOT’s, this meant shifting from an organization that functioned in a world of building new facilities, of historical data, of contemplative study and thorough review, and of 5-40 work-week schedules and staffing levels, to one of operating existing facilities, dealing with real-time data, algorithms, response plans, 24-7 work schedule and staffing levels.

·        Three-Step Cycle.  Most drivers do not appreciate that their driving behavior—the manner in which they operate their vehicles—can be a major cause of today’s endless traffic jams….that they are, in fact, part of the problem.  Trying to get that point across to the public is difficult at best, but if we are to break the chain of events that lead to congested freeways, the message must be delivered.  And we must convince drivers to change their travel patterns to help alleviate the situation.  This will be an enormous educational/public awareness undertaking; and there are many  who have serious doubts that it can be successful.  But, if we are to really gain the upper hand in the fight against congestion, success in this endeavor is a must.  We can ill afford not to try.

·        Funding.  Funding for freeway operations initiatives has always been a challenge, and it will remain so in the future.  It is closely tied to how well we sell the concepts of traffic management.  Because of tighter controls on money and a never-ending list of programs on which to spend it, we will continue to be challenged in the search for new sources of funding to continue expanding the existing infrastructure.  Such new concepts as partnerships between the private and public sectors, outsourced design/build/operate contracts for transportation infrastructure projects, and user-pay scenarios will bring about new opportunities for funding.  Expanding advertising, sponsorship, and “adopt-a-highway” schemes to include traffic management will present options for funding Operations.  Partnerships to sell or share data and video signals will continue to provide new opportunities to generate funds.