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LIFE-CYCLE GRAPHICAL REPRESENTATION OF MANAGED HOV LANE EVOLUTION Submitted for the 11th International HOV Conference October 27-30, 2002 Seattle, Washington Corresponding Author: Myron Swisher, P.E. Resident Engineer Colorado Department of Transportation 2000 South Holly Street Denver, Colorado 80222 (303) 757-9866 Fax: (303) 512-4350
[email protected] Co-authors: William L. Eisele, Ph.D., P.E. Associate Research Engineer Texas Transportation Institute Texas A&M University System 3135 TAMU College Station, Texas 77843-3135 (979) 845-8550 Fax: (979) 845-6008
[email protected] David Ungemah Manager of Technical Services Urban Trans Consultants, Inc. 1 Broadway Plaza; Suite A-200 Denver, Colorado 80203 (720) 570-3343 Fax: (720) 570-3363
[email protected] Ginger Daniels Goodin, P.E. Associate Research Engineer Texas Transportation Institute Texas A&M University System 1106 Clayton Lane, Suite 300E Austin, Texas 78723 (512) 467-0946 Fax: (512) 467-8971
[email protected] Submission Date: October 18, 2002
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ABSTRACT High-occupancy vehicle (HOV) lanes usually go through an evolution of stages in their life cycle. The typical evolution includes changes in demand levels from several modes including 2+ or 3+ carpools and vanpools, transit, and general-purpose vehicles. To ensure adequate usage, most facilities have started out with a designation of HOV 2+. In some cases, over time, HOV2 volumes have exceeded capacity of the facility, which has caused delays for transit vehicles. Therefore, there is an inevitable need for managing the hierarchy of facility users over time. This paper presents a graphical tool that illustrates the lifespan of a managed HOV lane, and it can be applied to a variety of existing and planned managed HOV lane projects. The graphic has previously been used in Colorado in communicating the managed lane concept to transportation professionals. Further, the graphic can be used to explain the historical operation of a managed HOV lane facility and the likely progression if current management policies remain in effect, based upon the experiences of similar facilities. Alternative management strategies can also be evaluated and compared with the graphical tool. The graphical representation of the managed HOV lane concept presented in this paper is anticipated to be valuable for transportation professionals in many areas (e.g., highway, tolling, and transit) in presenting and understanding operating scenarios for managed lanes over time and how they meet the goals of the facility. Finally, the paper presents applications of the life-cycle graphic to various facilities in the United States.
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INTRODUCTION Over time, a high-occupancy vehicle (HOV) facility may feature a variety of occupancy policies for the vehicles that utilize the facility. For example, an HOV2+ lane may eventually become congested due to growth in carpool traffic, and, subsequently require the conversion of the facility to a three-person or more (HOV3+) carpool facility. A variety of institutional interests can likewise be expected to play a role in the development of these occupancy policies. The graphical representation of managed HOV lanes, as presented in this paper, can be used as a tool for managing these relatively disparate interests. The graphical tool presented in this paper illustrates the lifespan of a managed HOV lane, and it can be applied to a variety of existing and planned managed HOV lane projects. Further, the graphic can be used to explain the historical operation of a managed HOV lane facility and the likely progression if current management policies remain in effect, based upon the experiences of similar facilities. Alternative management strategies can also be evaluated and compared with the graphical tool. This paper describes the evolution of the HOV lane to manage the hierarchy of users. It visually illustrates the “managed HOV lane” concept as SOV and HOV tolling can effectively use the excess capacity available at various stages of the managed lane evolution. The goals and objectives of any managed HOV lane can be varied and must be considered. This paper describes how the managed HOV lane can be operated over time to satisfy the goal of not impeding transit or HOV users in the short- or long-term. Further, some managed HOV lanes have a goal of revenue generation. These goals, and others, are all achieved with timely tolling strategies for the hierarchy of users while generally favoring transit. The graphical tool described in this paper can illustrate the operation of a facility with different goals and objectives and related policies. The transit community, in particular, has a significant investment in managed HOV lanes throughout the United States. Not only has the Federal Transit Administration (FTA) contributed to the development of managed HOV lanes in various urban areas, but also individual communities and states have invested significant funds in the infrastructure and marketing of managed HOV lanes. Although the concept has been successful in many urban areas, it has not been universally successful. Some managed HOV lane facilities have suffered from a lack of full capacity utilization by carpoolers especially upon opening, and thus, there has been the temptation by elected officials to convert the managed HOV lanes to general-purpose lanes. In an effort to better utilize existing HOV infrastructure and continue to maintain an HOV preference on the facility, while acceding to these political interests, some communities have pursued the concept of high-occupancy toll (HOT) facilities. The use of pricing, along with setting distinct project objectives that are favorable to transit, has shown that managed HOV facilities with HOT policies can simultaneously benefit transit riders, carpoolers, and the free flow of traffic on the facility. The degradation of travel speeds on the managed HOV lane is a concern of transportation professionals over the long term. Transportation professionals have had difficulty communicating how managed HOV facilities evolve in their operation. This paper presents a graphical tool that has been used successfully in Colorado to demonstrate the concept of managed HOV lanes and the evolution of occupancy policies over time.
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DEFINING MANAGED HOV LANES AND THE USER HIERARCHY High-occupancy vehicle lanes have offered a mobility option on congested corridors for eligible vehicles in many large metropolitan areas. In recent years, there has been increased national interest by individuals and agencies that plan, design, operate and maintain HOV facilities to identify a term that encompasses the different facility types available and also provides the flexibility for changes in eligibility or use of variable pricing strategies. To reflect this flexibility, the term “managed HOV lane” is used in this paper. Therefore, managed HOV lanes include all traditional HOV lanes, high-occupancy toll (HOT) lanes, value-priced lanes and bypass lanes. This new terminology is meant to constitute a lane or group of lanes where preference is given to HOVs, but where a combination of operating and design strategies are also employed to ♦ ♦ ♦ ♦
optimize the use of available roadway capacity; maintain free-flow conditions; maximize person throughput; and achieve corridor and community goals.
These facilities can be designed for flexibility, so that operations can be modified over time as conditions change. Management tools, such as the operational and design strategies listed below, are used to regulate demand in the managed HOV facility: ♦ ♦ ♦ ♦ ♦
Variations in vehicle group eligibility in addition to HOV (e.g., single-occupant vehicles (SOV), inherently low-emitting vehicle (ILEV), trucks); Period-based eligibility of designated vehicle user groups (e.g., time-of-day, day-ofweek); Pricing (using electronic toll collection); Physical control (e.g., continuous barriers to limit direct access, gates), and Operational control (e.g., lane assignment, reversible lanes).
Clearly, it is possible that a managed HOV facility can have many different objectives. Because of community and project goals, it is possible that these objectives differ from the traditional HOV project objectives. For example, an agency with a primary objective of increasing person throughput and average vehicle occupancy using managed HOV lanes may also wish to maintain free-flow conditions while optimizing vehicle utilization of the facility. A combination of operational and design strategies, such as those listed above, could be employed to achieve these objectives. An agency also may have a financial goal to provide revenue that can support capital and/or operating costs. As such, vehicle eligibility and pricing structure would reflect that goal. It is for these reasons that the graphical representation presented in this paper is particularly valuable. The graphical representation can be used to identify future operations consistent with project goals and objectives, operating strategy, and the user groups involved. A key concept in implementing a managed HOV approach is the development of a “hierarchy of users” that represents priorities for vehicle group eligibility in a managed HOV facility. The final decision on eligible users and their importance will depend upon the characteristics of the corridor and project/community goals. In addition to HOVs, which
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includes transit or bus rapid transit, alternative user groups are SOVs, trucks, inherently lowemitting vehicles (ILEVs), taxi, emergency vehicles, and motorcycles. A typical approach would be to provide bus transit operations the highest priority, followed by HOV3+ (vanpools included), then 2-person carpools, and finally toll-paying single-occupancy vehicles. It can be difficult to communicate to numerous stakeholders how these users will be allowed to use a managed HOV lane facility as demand from different users changes over time. The objective of this paper is to present a graphical tool that can be used to communicate how the demand from these user groups is managed over time. LIFE-CYCLE REPRESENTATION OF THE MANAGED HOV LANE The graphical representation of the lifespan of a managed HOV facility is depicted in the following series of figures. Figure 1 shows the excess capacity that typically exists at the opening of a traditional HOV lane with an HOV 2+ designation (as depicted by point A in Figure 1). It is clear that excess capacity exists as depicted in this scenario. Over time, for the more successful HOV lanes, growth in HOV traffic will overwhelm the facility, reaching what can be termed the “critical operating threshold.” The critical operating threshold (COT) is the traffic volume beyond which free-flow conditions begin to degrade (point B on Figure 1). Forced with either enduring travel time degradation in the lanes, or changing occupancy policies, transit authorities may choose the latter. This preserves the travel time advantage of the facility, but it does come at a price. As shown at point C, the amount of excess capacity that remains after the policy change is even greater than at the opening of the facility. If only transit and HOV3+ are permitted after point C, very low volumes will likely be present on the facility. Although some two-person carpoolers will be able to find a third passenger, potentially through “slug lines” or spontaneous carpooling in very congested situations (1), the majority of the capacity in the HOV facility will remain unused. This leads to the “empty lane syndrome,” in which angry citizens and elected officials publicize the fact that the HOV lanes are greatly underutilized, even at the peak of rush hour. In contrast to the traditional HOV lane, Figure 2 shows the lifespan of a managed HOV lane. The managed HOV lane has a key component different from that of traditional HOV lanes: the use of variable pricing and other management tools. In this scenario, SOVs are permitted access to the managed HOV lane, provided they pay the prevailing toll. Through the use of dynamic pricing, which varies the toll with the level of congestion on the managed HOV lane, the number of SOVs who use the facility is never allowed to exceed the critical operating threshold. As depicted by point 1 on Figure 2, HOV traffic growth over time reduces the availability of capacity for toll-paying SOVs. At such a point where the prevailing toll charge would exceed a reasonable charge (point 2), SOVs would no longer be permitted access to the managed HOV lane. When the growth in HOV traffic exceeds the critical operating threshold, authorities would once again change the occupancy policies for the facility. However, as shown by point 3, the excess capacity is sold to both two-person carpools as well as single-occupant vehicles. In the managed HOV lane scenario, excess capacity is regulated to ensure a balance between maintaining free-flow conditions and avoiding the “empty lane syndrome.” Therefore, the excess capacity is much more effectively utilized, further enhancing the overall effectiveness of the managed HOV facility.
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Figure 1. The Lifespan of an HOV Facility
Figure 2. The Lifespan of a Managed HOV Lane
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The tolling of HOV2s and SOVs achieves the following: Encourages the continuation of two-person carpools, even after the facility has been converted to a 3+ occupancy policy; ♦ Maximizes the utilization of excess capacity, eliminating the perception of wasted space; and ♦ Prevents the empty lane syndrome from becoming a political threat. ♦
The graphic shows a clear hierarchy in vehicular class at point 3 and further into the future of the facility. The highest priority is bus service, followed by HOV3+, HOV2, and tolled SOV. Whenever traffic growth occurs in higher priority classes, lower priority classes will be prohibited from the managed HOV lane facility. This is indicated by the eventual termination of access by toll-paying SOVs in the graphic. The description of the life-cycle representation of a managed HOV lane presented above is valuable in displaying the hierarchy of vehicle classes and displaying the potential outcome of policy decisions. As described in the previous section in defining a managed HOV lane, the objectives of a managed HOV lane include maximizing the available roadway capacity, maintaining free-flow conditions, maximizing person throughput, and achieving corridor and community goals. Therefore, the graphical representation provided in this paper provides a tool for transportation professionals to identify their options as congestion on the facility increases, and to present to stakeholders that doing nothing creates unacceptable conditions based upon the objectives of a managed HOV facility. APPLICATIONS The lifespan of the managed HOV lane graphic presented in this paper can be applied to a variety of existing and planned managed HOV lane projects in the United States. Indeed, the graphic has already been utilized in communicating the managed HOV lane concepts to transportation professionals (2,3). It provides a clear, simple, non-technical pictorial representation of how excess capacity can be better managed and utilized, enhancing the overall effectiveness of the managed HOV lane facility. This section provides illustrations of how the life-cycle graphic can be applied to various managed HOV lane facilities in the United States. Colorado – I-25 / U.S. 36 Value Express Lane Study The managed HOV lane evolution graphic presented here was originally developed for the I-25 / U.S. 36 Value Express Lane Study, conducted by the Colorado Department of Transportation (CDOT) in 1999 – 2001 (4). The concepts provided here were used to inform the transportation community of the application of managed HOV lanes on Interstate 25’s Downtown Express HOV facility. In response to questions from transit professionals, this graphic was used to demonstrate how value pricing of single-occupant vehicles could exist on the Downtown Express without degrading the travel times of bus riders and carpoolers. Figure 3 shows the application of the graphic to the Downtown Express. Existing traffic counts from the opening of the two-lane reversible facility in 1994 and collected through 2001 were used in providing realistic data for the graphic.
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Figure 3. Colorado – I-25 Downtown Express Lanes
The graphic starts with point 1 where the Downtown Express opened for use by HOV 2+ and bus riders in 1994. CDOT and Regional Transportation District (RTD) engineers determined that 2,300 vehicles per hour (1,150 vphpl) would generally constitute the critical operating threshold for the Downtown Express. The critical operating threshold for this facility is controlled by ingress and egress to the facility at the downtown Denver end. With substantial investment in additional access points, the critical operating threshold could approach 3,000, or level of service (LOS) C, for this two-lane freeway segment. As shown by point 2, pricing policies are anticipated to be active by 2004. This policy would allow single-occupant vehicles to access the Downtown Express by paying the dynamically priced toll. The excess capacity that was previously unused is now used by toll paying customers. However, the growth in HOV traffic could eventually overwhelm the available capacity in the Downtown Express for SOVs. As shown at point 3, SOVs would temporarily be prohibited from utilizing the facility in approximately 2012, when the dynamically-priced toll required to maintain free flow would exceed a reasonable price. Given projections, within four years, HOV traffic growth will likely reach and exceed the critical operating capacity for the Downtown Express. As such, and as shown at point 4, the facility will likely change its primary occupancy policies. Three-person carpools or more (HOV 3+) and transit riders will continue to utilize the facility without charge, however, SOVs and HOV 2+ carpools will be permitted access with payment of the dynamically priced toll.
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Houston HOT Lanes – Katy (I-10) and Northwest (US 290) Freeways Figures 4 and 5 illustrate the graphical format as applied to two operating HOV/HOT lanes in Houston, Texas. Both facilities are part of a larger HOV system designed primarily to serve bus transit. The development of the system began two decades ago as the result of a partnership between the Texas Department of Transportation (TxDOT) and the Metropolitan Transit Authority of Harris County (METRO), which is the agency that operates and enforces the HOV lanes and the peak hour HOT lane operations. The Katy HOT Lane, as shown in Figure 4, began in 1984 as a 13-mile single-lane reversible HOV facility opened to buses. After gradual modification of the eligibility over time to HOV4+ and HOV3+ (see point 1), HOV2+ were allowed in 1987. Over a period of less than two years, HOV2+ volumes grew to a point that the HOV lane became congested, resulting in a degradation of bus operating speeds. As a result, the HOV3+ restriction was reinstated during peak morning and evening hours, as shown at point 2. Although bus operating speeds returned to acceptable levels, the HOV lane operation was criticized for being underutilized. In January 1998, the HOT lane program was initiated during the peak hour 3+ restrictions to allow HOV2s to “buy in” to the facility at $2.00 per trip, increasing utilization during the restricted periods (5). The Northwest HOT Lane shown in Figure 5 is also a single-lane reversible HOV lane that is 13.5 miles in length. It was opened with an HOV2+ eligibility in 1988 (point 1), and gradually reached critical operating levels until the HOV3+ restriction was implemented during peak hours in 1999 (point 2). In 2001, the HOT lane program was initiated to offer access to HOV2s during the restricted period, as shown at point 3, with HOV2s paying a $2.00 toll per trip (5). A critical operating threshold described in vehicles per hour has not been officially designated for the Houston HOV system. Rather, each facility is examined individually in terms of operating speeds, which can vary depending on the geometric design and the location and spacing of access points. A critical operating threshold of 1,300 vehicles per hour is presented in both Figures 4 and 5 as approximate representation of that operating speed threshold. El Monte Busway – San Bernadino Freeway, Los Angeles The El Monte Busway is the oldest freeway HOV facility in the Los Angeles area. Buses have always been a key element and carry over 18,000 passengers per day on the facility. A history of operating conditions on the busway is depicted in Figure 6. After operating as a busonly and HOV3+ facility for more than two decades (point 1), the California Legislature passed a bill lowering the vehicle occupancy requirement to HOV2+ beginning in January 2000 (point 2). Vehicle volumes on the Busway increased during the trial period, causing a substantial decline in operating speeds, a decline in the number of persons carried, and a significant impact on bus operations. At the same time, travel conditions in the general-purpose lanes did not improve noticeably. As a result of these conditions, legislation was passed reinstating the HOV3+ requirement during peak hours, with HOV2+ remaining in effect at all other times (point 3) (6).
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Figure 4. Texas – I-10 (Katy) HOV/HOT Facility
Figure 5. Texas – US 290 (Northwest) HOV/HOT Facility
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Figure 6. California – El Monte HOV Facility
The 1,300 equivalent vehicles per hour operating threshold on the El Monte Busway is provided in a 1981 amendment to the operating agreement between the State of California and the Southern California Rapid Transit District (7). The critical operating threshold is based on an equivalent vehicle volume, which is computed by adding the hourly volume of carpools and the hourly volume of buses multiplied by a factor of 1.6. When the equivalent vehicle volume approaches 1,300 vehicles per hour, Caltrans will initiate studies to determine appropriate actions to ensure that the critical operating threshold is not exceeded. California – San Diego I-15 FasTrak Facility The I-15 HOV Facility, northeast of downtown San Diego, shows a relevant application of the lifespan graphic. The I-15 FasTrak facility features two reversible managed HOV lanes. Since its opening in 1988, the facility was largely unutilized. As shown by point 1 of Figure 7, HOV 2 usage constituted only 60% of peak period capacity in the facility. Within a few years, echoing the reduction of mandated trip reduction programs in California and general rideshare trends nationwide, use of the facility actually declined in the early 1990s, as shown by point 2 (8). In addition to the declining use of the I-15 HOV facility, local politicians were interested in establishing new transit service in the northeastern San Diego metropolitan area. Using a grant from the Federal Highway Administration, San Diego initiated a High Occupancy / Toll policy for the I-15 facility. Renaming it FasTrak, I-15 was able to generate more than 500 additional vehicles in the peak period for the first year of operation, as shown in point 3.
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Furthermore, new revenues raised by the HOT lanes were allocated to new transit service on the corridor, providing a modal option that had not previously existed (8).
Figure 7. California – I-15 FasTrak Facility
I-15 FasTrak uses dynamic pricing to manage demand for the facility, including an allowance for extremely high toll rates in emergency situations. As such, the operating conditions on the corridor have reached or exceeded the critical operating threshold less than 2 percent of the time. Due to relatively low HOV growth (as compared to the Texas and El Monte examples), removal of SOVs from the facility is not anticipated within the short- and mediumterm. SOV traffic can be managed via price; HOV2 growth will not reach the critical operating threshold within the planning horizon, as shown by point 4. Knowing this, San Diego is currently in the process of designing an expansion to the facility’s northern end, extending HOT lanes and providing an even greater transit service for the corridor. CONCLUSIONS AND DISCUSSION In presentation to transit advocates, the lifespan of the managed HOV lane graphic helps clarify when and why single-occupant vehicles will eventually be excluded from the facility. The graphic illustrates the normal evolution of a managed HOV lane. It shows the efficient use of this transportation tool with no negative impact to transit. As proven by HOT lane projects in Houston, the implementation of managed HOV lane policies can greatly ease the political outcry against HOV lanes when they are perceived to be
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inefficient by allowing them to evolve to manage the changing demand. Furthermore, in many states, there has been political pressure to eliminate HOV lanes altogether, primarily in response to the empty lane syndrome. For select facilities in New Jersey and Virginia, HOV lanes have been eliminated entirely. It could be argued that these actions could have been prevented if managed HOV lane policies had been permitted, allowing for better utilization of the facility to manage the demand appropriately over time. The value of the graphical representation in planning a managed HOV facility is in providing a vision of evolving operating scenarios over time. This vision helps planners, engineers and operators avoid the pitfalls that have led to termination of HOV lanes in the past. It offers a means for consciously establishing priorities and critical operating thresholds for the most important user groups allowed in the facility. This can lead to quick, intentional, and institutionalized decision-making as travel patterns change and operating conditions in the facility fluctuate over time. As presented in this paper, the primary application of the life-cycle graphic is to identify different strategies for managing demand, especially through pricing scenarios. Alternatives analysis using the graphic could also include evaluating the life cycle of different geometric alternatives, including the location of enforcement, ingress/egress points, or other geometric characteristics that may alter traffic flow. This could also include preparing the graphic for specific critical segments of the corridor. Projected person throughput could also be used instead of projected traffic volume along the y-axis. From an operational standpoint, trucks, taxi or other traffic could be made eligible for tolling and could be evaluated with the graphical tool presented here. Finally, the graphical representation offers a valuable tool for communicating to a variety of audiences the “managed” aspect of an evolving HOV lane over its life. Several examples are provided in this paper, and the graphic can be applied to any planned or existing managed HOV facilities by modifying the critical operating threshold and user hierarchy to match local conditions, goals and objectives.
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REFERENCES 1. Speilberg, F.L., Shapiro, P.S. Mating Habits of Slugs: Dynamic Carpool Formation in the I95/I-395 Corridor of Northern Virginia. Transportation Research Record 1711, pp. 31-38. 2000. 2. AASHTO Guide for the Design of Managed High-Occupancy Vehicle Facilities. Draft, 2002. 3. I-95 High Occupancy Vehicle (HOV) Workshop. Summary of workshop proceedings. Florida Department of Transportation, District 4 - Office of Modal Development. April 24, 2002. 4. Colorado Value Express Lanes Feasibility Study. Final Report. Colorado Department of Transportation. 2001. 5. Houston High Occupancy Vehicle Lane Operations Summary. Metropolitan Transit Authority of Harris County. December 2001. 6. Turnbull, K.F. Effects of Changing HOV Lane Occupancy Requirements: El Monte Busway Case Study. Draft report to FHWA, August 2002. 7. State of California. Amendment to Agreement Between State of California Department of Public Works and Southern California Rapid Transit District, 1981. 8. FasTrak Phase II Year Three Traffic Study. San Diego Association of Governments. September 2001.
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