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Priced Managed Lane Guide

CHAPTER 6. Design

Design considerations for priced managed lanes will inevitably be driven by the corridors in which they are located. Of the 14 priced managed lane facilities that were operational in May 2012, all but one were built in corridors with pre-existing HOV lanes. As a result, their designs differ significantly as they required the retrofitting of highway corridors with constrained design settings and that included earlier design exceptions that were previously approved for a specific set of operation rules and requirements. A few operational facilities, including the I-10 Managed Lanes in Houston and the I-15 Express Lanes in San Diego, involved reconstruction of the corridor segments where the HOV lanes existed. For these and other projects where new lanes were constructed, the physical design and construction of the lanes is similar to that of any full standard highway improvement, incorporating few trade-offs between lane width, shoulder width, access, and physical separation. Most other projects have involved the retrofit of existing HOV facilities involving significant design exceptions.

6.1.1 How Design of Managed Lanes Differs From General-Purpose Lanes

As with general-purpose lanes, the design and construction of managed lanes involves a variety of improvements to widen or otherwise alter the existing roadway, including utility coordination and relocation, the installation of drainage systems, earthwork, paving, the construction of ramps, overpasses and bridges, and adding appropriate signage and striping. In some cases new express lanes have been built within the median by removing shoulders. In others such as IH 10 in Houston and I-15 in San Diego, new right-of-way may be needed. In either case, modifications to some components of the existing roadway are likely.

Outside of new lane construction, the conversion of an existing general-purpose or HOV lane to priced managed lane use can be less complicated if the prior design is found to be able to support tolled traffic without safety ramifications. About half the HOV lanes in the United States have been able to apply full design standards commonly found in the AASHTO Green Book and AASHTO’s 2004 Guide for High Occupancy Vehicle Facilities, and this would likely support any mix of traffic. However many projects have been implemented in very tight design settings where lane and shoulder widths may be reduced. A safety analysis may be required to determine what design and/or operational changes may be needed in order to support a changes in traffic volume if involving an HOV lane conversion. For added capacity, such analysis will likely focus on the access locations of this separate roadway system.

In order to provide better traffic service levels, support higher traffic volumes and discourage toll violations, managed lanes are typically accompanied by some form of access control, particularly for non-barrier-separated projects that may have been operating on a part-time (i.e., peak period only) basis. However, recent projects in Utah and Minnesota have utilized a more continuous access policy that allows for greater ingress and egress opportunities across greater lengths of the facilities.

As shown in Table 6-1, the basic cross-section components of managed lanes are similar to those of general-purpose and HOV lanes. To date all priced managed lanes existing or proposed are configured next to the center median barrier to serve longer distance trips. Some utilize HOV lanes that were implemented by converting median shoulders. The design of priced managed lanes may also require full roadway reconstruction, but often such projects must fit within an existing freeway. Existing roadway constraints may limit the ability to meet standards. In many cases, right-of-way limitations and bridge structures make it impossible to meet all desired design standards. Compromises, often codified as design exceptions, are often required that involve prudently justified deviations from desired practice. Specific design may also depend on local conditions, accepted practice and other issues. Realizing that applying desirable design elements may not always be possible, this guide includes horizontal design attributes that brackets both desirable elements and reduced elements often applied in constrained settings. Such trade-offs have been practiced for more than 40 years on managed lane designs, so there is considerable operational experience associated with many of these elements.

Table 6-1: Managed Lane Cross Sections
Cross Section Element Typical dimensions found in Professional Design Guidance
Lane Width 12 feet (3.7 meters)
Shoulder Width (Right and Left) 10 feet (3.0 meters) preferable
2 feet (0.6 meters) minimum (dependent on number of lanes, type of operation, sight distance)
14 feet (4.3 meters) for enforcement / apprehension
Buffer Width (if desired for non-barrier-separated operation) 2 to 4 feet (0.6 to 1.2 meters)
Sight Distance Standard stopping sight distance for facility type
Safety considerations Crash attenuation for exposed barrier ends
Transition treatments with HOV or general-purpose lanes
Adequate access opening lengths (minimum 1,200 feet [366 meters])

Source: AASHTO, Guide for High Occupancy Vehicle (HOV) Facilities, October 2004

The physical configuration and operation of managed lane installations varies greatly and is driven by travel demand and physical constraints. They may involve single or dual (or even greater) directional lanes operated on a concurrent (with the flow of traffic) or reversible-flow (inbound in the AM, outbound in the PM) basis. Concurrent operations typically provide one lane in each direction, regardless of the traffic peaking that may occur, and as such, these lane designs are symmetrically oriented around the median centerline. Reversible operations on freeways require full concrete barrier separation. Cross sections for these different configurations are provided in the figures below.

Figures 6-1, 6-2, and 6-3 provide representative cross sections for concurrent-flow and reversible-flow managed lanes. These dimensions are reflected in guidance found in National Cooperative Highway Research Program (NCHRP) 414, HOV Systems Manual and AASHTO HOV Design Guide, and correspond to current practice for many HOV lane treatments nationwide. Desired designs generally reflect those associated with a permanent or new facility, and typically meet all AASHTO and local design standards. Reduced designs reflect an inability to meet desired criteria due to a variety of constraints that have generally been determined to be very difficult or impossible to address. Consideration of reduced designs should be considered on a case-by-case basis based on sound engineering practice and in context with operational objectives and trade-offs. The reduced elements presented in this Guide, while found on some and perhaps many projects nationally, are not intended as a prescribed standard of practice.

Figure 6-1 shows cross sections for a single lane reversible priced managed lane facility located in the median of an existing highway, such as projects operating on various freeways in Houston.

Figure 6-2 provides similar information for a two-lane, reversible-flow, median facility similar to that found on I-394 in Minneapolis, I-25 in Denver, and the first generation I-15 facility in San Diego (1995-2011).

Finally, Figure 6-3 shows typical cross sections for a dual-lane concurrent-flow facility similar to the SR 91 Express Lanes in Orange County, California and I-95 Express Lanes in Miami, Florida.

Figure 6-1: Cross Section for a Single Lane Reversible-Flow Priced Managed Lane

This graphic shows two cross sections of a single lane reversible flow priced managed lanes.  The first shows a cross section of total width of 28 to 32 feet as desirable and the second shows a reduced cross section of only 20 feet width.
Source: AASHTO, Guide for High Occupancy Vehicle (HOV) Facilities, October 2004

Figure 6-2: Cross Section for a Dual-Lane Reversible-Flow Priced Managed Lane

This graphic shows two cross sections of Dual-Lane Reversible-Flow Priced Managed Lane.  The first shows a cross section of total width of 44 feet with 22 feet in the middle for reversible lanes as desirable and the second shows a reduced cross section of only 36 feet width and the same 22 feet in the middle for reversible lanes.
Source: AASHTO, Guide for High Occupancy Vehicle (HOV) Facilities, October 2004

Figure 6-3: Cross Section for a Dual-Lane Concurrent-Flow Priced Managed Lane

This graphic shows three cross sections of Cross Section for Dual-Lane Concurrent-Flow Priced Managed Lane.  The first shows a cross section of total width of 62 feet with a 12 foot managed lane on each side of a barrier and 14 foot shoulder.  The second shows a 54 foot cross section with 12 foot managed lanes and barrier with a 10 foot shoulder.  The third shows a reduced cross section of only 34 foot width and the same 12 foot lanes separated with a barrier section of six feet.
Source: AASHTO, Guide for High Occupancy Vehicle (HOV) Facilities, October 2004

Source: AASHTO, Guide for High Occupancy Vehicle (HOV) Facilities, October 2004

6.2 Access

Access to a managed lane facility, and the extent to which it is controlled, is a fundamental issue in designing and operating managed lanes. Cost, operational, safety, and enforcement trade-offs associated with the different levels of access control must be considered. There are multiple approaches to providing access to managed lanes: continuous, restricted at-grade access, and grade-separated access. Recently there has also been interest in continuous access where motorists could enter or exit priced managed lanes at any point. The use of continuous access for priced lanes has implications on the number of tolling points, ETC installations and enforcement practices. While tolls are often collected downstream of access points, additional access points in intermediate locations are now also common on newer priced managed lane facilities. This follows a 30-year legacy of intermediate access on HOV lanes.

6.2.1 At-grade Access

There are three commonly used types of restricted at-grade access for managed lanes:

  • Weave Zones. This type of access is generally used on facilities that use buffer separation. A short break in the buffer striping allows for simultaneous ingress and egress. Figure 6-4 shows weave zone access to the SR-167 Express Lanes in the Seattle area. Weave zones are the most common form of at-grade access used on priced managed lane facilities in the United States.
  • Weave Lanes. This type of access allows for both ingress or egress, but is facilitated by a lane designated for the weave. The inclusion of a weave lane minimizes the potential for unstable flow along the weave due to the speed differential between the managed lane and general-purpose lanes. Weave lanes are the primary form of access on barrier-separated facilities (due to the need to segregate opposing flow movements with barriers) and may be found on the I-15 Express Lanes in San Diego.
  • Slip ramps. Separated ingress and egress utilizing dedicated acceleration and deceleration lanes. This design separates operational maneuvers and provides drivers with a better opportunity to adjust their speed to match that of the traffic stream into which they are merging. This further reduces the potential for unstable flow. Given that a variety of at-grade slip ramp design approaches may be used, Caltrans has developed access guidance to help support more consistent use of these access treatments (Figure 6-5). Slip ramps may be found on the I-680 Express lanes in Alameda County, California (2010), shown in Figure 6-6 shows slip ramp access to the I-10 Katy Freeway HOT lanes in Houston (2008), which are separated from the general-purpose lanes by pylons.

Figure 6-4: Weave Zone Access Treatment, SR-167 Express Lanes, Seattle, WA

A photograph showing the left lane of an interstate with a double white stripe lane marking changing to a dashed white stripe where merging is allowed.
Source: Washington State Department of Transportation

Figure 6-5: Managed Lane Slip Ramp Design Alternatives

A graphic showing lane configurations for managing slip ramps for a typical ingress, a second graphic shows a slip ramp for only egress, a third graphic shows combined ingress and egress with a weaving zone, and the fourth shows combined ingress and egress with a weaving lane.
Source: Caltrans Traffic Operations Policy Directive, 2011

The type of at-grade access opening that is selected will depend upon the existing and planned roadway geometrics and the amount of traffic expected to use the opening. In all cases, openings should be located and designed in a way that will not produce adverse impacts to the managed lanes and the parallel highway lanes. The locations of at-grade access openings need to be closely coordinated with highway entrance and exit ramps and allow adequate room for motorists to complete weaving movements when moving between the general-purpose and managed lanes and an entrance or exit ramp. For example, as of 2011, Caltrans recommends a buffer/barrier opening of at least 2,000 feet, and a weaving distance of at least 800 feet per lane between the upstream and downstream ramps and the opening. [8] When determining the locations of slip ramps, local topography, lines of sight, and operating characteristics of adjacent lanes need to be taken into consideration. Where heavy weaving between the managed lanes and interchange ramps is expected, grade-separated access may be desirable based on traffic engineering analysis of the demand and roadway geometrics. This may be especially true where multilane managed lane treatments are being considered.

Restricted at-grade access to a striped or barrier-separated managed lane is a cost effective approach to providing controlled access to the managed lane facility. At-grade access opening control ingress and egress to and from the managed lane, minimize traffic service impacts in the managed lane, and control weaving movements on the parallel highway. While they limit the need for expensive ramp structures, they may require additional pavement area, and can require modifications to existing bridges and sign structures. Because access is limited to certain locations upstream and downstream of interchange ramps, there is the potential for bottlenecks to form near access points.

Figure 6-6: Slip Ramp Access to the I-680 HOT Lane, Alameda County, CA

A photograph of an interstate section showing striping of slip ramp access in the left lanes.
Source: Parsons Brinckerhoff

Figure 6-7: Slip Ramp Access to the I-10 Katy Freeway HOT Lanes in Houston

A photograph of an interstate lane with single stripe lane slip ramp leading to the HOT lanes.
Source: Parsons Brinckerhoff

6.2.2 Near-Continuous Access

Several projects have moved forward with less restriction on access, employing more limited areas where traffic cannot weave back and forth between the managed lane and the general-purpose lanes. The first project to apply this access approach was the I-394 MnPASS project in Minneapolis, shown in Figure 6-8 More recent projects include I-35W in Minneapolis and I-15 in Salt Lake City. I-15 is 42 miles long and provides 19 access points. The access points are marked by white skip striping, while the rest of the express lanes are marked with double-solid white lines. The access points range from 3,000 to 9,000 feet long, giving plenty of space for users to enter and exit the lanes regardless of the prevailing operating condition in mixed-flow lanes. Given the number of access points and length of access zones, essentially half of the project length allows continuous access, and the frequency provides one managed access for every interchange ramp on the right side. I-35W has an even greater percentage of near-continuous access lane-miles—with over 70 percent of the facility featuring this design.

In both cases, frequent and appropriately located toll zones limit violations, and the violation levels to date have been acceptable without added enforcement. Additionally, near-continuous access designs permit weaves between the managed lanes and general purposes to be more distributed, thereby reducing the effect of conflict at access openings. Finally, the need for signage is reduced, which in turn can be a positive effect upon capital cost requirements. A number of project sponsors are exploring this approach to access control on managed lane conversions in the San Francisco Bay Area, Phoenix, Seattle, and Minneapolis / St. Paul.

Figure 6-8: Near Continuous Access on I-35W in Minneapolis

A photograph of an interstate where the left lane has an overhead sign indicating an HOV lane.
Source: Minnesota Department of Transportation

6.2.3 Grade-Separated Access

Conventional wisdom in highway engineering holds that the greatest efficiency, safety, and capacity is achieved when conflicting movements are grade separated. Grade-separated access for managed lanes is generally reserved for high volume movements and those serving linkages to transit facilities. Their inclusion can be found in any project design since they greatly reduce weaving and merging movements for vehicles entering or exiting a facility. In addition, the ramps provide acceleration and deceleration areas, which allow high-speed merges and diverges. Grade-separated options include median drop ramps from overpasses or direct freeway-to-arterial or freeway-to-freeway connections. Figure 6-9 illustrates a freeway-to-freeway connection in Miami, FL for the I-95 Express Lanes. Figure 6-10 shows a direct connection ramp from the I-10 HOV lane in downtown Phoenix to the local street grid, while Figure 6-11 shows the direct HOT-HOV connector from the I-110 south of Los Angeles to I-105, which provides the main highway connection between downtown Los Angeles and Los Angeles International Airport (LAX). Layouts for these examples and others can be found in the HOV guides listed later in this section. Many multilane priced managed lane facilities being planned or built in Georgia, Virginia, Florida, and Texas are relying on grade-separated access, in keeping with their high anticipated volumes associated with ingress and egress.

Access and egress to and from managed lanes should be located and designed to minimize conflicts with mainline general-purpose traffic. As with other highway facilities, managed lane access and egress, whether it be continuous or restricted or direct-access features, should meet local practice and to the extent possible, reflect guidance provided by AASHTO. A summary of project design elements is provided in Table 6-2.

Figure 6-9: I-95 Express Direct Connector Ramp in Miami

A photograph of an interstate section with HOV lanes and a direct connector ramp.
Source: Parsons Brinckerhoff

Figure 6-10: HOV Direct Connector Ramp to Downtown Phoenix

A photograph of a single lane of connector interstate separated by barriers.
Source: Parsons Brinckerhoff

Figure 6-11: I-110-I-105 HOV Direct Connector Ramp in Los Angeles

A photograph of a single interstate lane connecting HOV lanes.
Source: Parsons Brinckerhoff

Table 6-2: Summary of Managed Lane Design Attributes
Project/Route Type of Operation Intermediate Access Attributes Tolling Attributes Separation
SR 91, Orange County ETL, 2 lanes each direction (full time) None One tolling zone Traffic channelizers
I-15 extension, San Diego HOT, 2 lanes each direction, with center lanes reversible (convertible to 2-2 or 3-1) At 10 locations northbound and 8 locations southbound, combined egress/ingress with continuous transition lane in-between; plus five (grade-separated) direct-access ramps Distance-based tolls (skewed, per-mile dynamic pricing). Toll zones located between access locations and at all entrance locations. Price varies by location Southern 16 miles has fixed concrete barriers with significant number of intermediate at-grade slip ramps in each direction. Moveable median barrier in Express lanes. Northern 4 miles are buffer separated.
US 290, Houston 1 lane reversible Only through DARs Fixed price, only one toll zone Concrete barriers
I-10, Houston, open 3/09 ETL, 2 lanes each direction (full time after 3/09) At 2 locations, combined egress/ingress with continuous transition lane in-between Toll zones between access locations with declaration lanes Traffic channelizers
I-15, Salt Lake City 1 concurrent lane each direction (full time) Frequent (2-mile spacing) and long (3000-9000 ft) weave access zones. 400- ft avg. Buffer frequently violated. Used to be continuous access for HOV only. Fixed monthly fee with permit, will transition to dynamic pricing at tolling zones None, paint markings only
I-25, Denver Mostly 2 lanes reversible (part-time) Only through DARs One tolling zone with declaration lane Concrete barriers
I-394, Minneapolis Mostly 1 concurrent lane, 2 lanes reversible last 4 miles (part-time, peak direction) 2-3 in each direction; weave zone Toll zones between access locations None in concurrent section, paint markings only, reversible section has concrete barriers.
SR 167, Seattle area 1 concurrent lane each direction (part-time) 5 northbound, 4 southbound; weave zone Toll zones to assemble trips between access locations None, paint markings only
I-95, Miami ETL, 2 lanes each direction (full time) None in Phase 1 Single toll zone in Phase 1 Traffic channelizers
I-10 (El Monte) Los Angeles, open 2013 Mostly 2 concurrent lanes each direction (full time) Combined ingress/egress weave zones, no transition lanes Toll zones between access locations Concurrent section has paint markings only; separated section is in an independent right-of-way.
I-110 (Harbor) Los Angeles, open 2012 1-2 concurrent lanes each direction (full time) Combined ingress/egress weave zones, transition lanes being added through restriping Toll zones between access locations Concurrent section has paint markings only; elevated section is independent.
I-95, Maryland 1 barriered lane each direction (full time) Very limited-several slip ramps through barrier alignment Several toll zones Concrete barriers
I-85 Atlanta, open 2011 (I-75 being studied) 1 concurrent lane each direction (full time) May remove some intermediate access openings, frequent vehicle readers and cameras, weave lanes, no transition lanes Frequent toll zones None, paint markings only
I-15, Provo 1 lane each direction Access zones similar to other portions of I-15 HOT lanes, weave lanes, no transition lanes Toll zones between access locations None, paint markings only
I-35W, Minneapolis Northbound median shoulder (part-time) None Single toll zone None in concurrent section, paint markings only
I-77, Charlotte (study pending) 1 concurrent lane each direction (full time likely) Multiple access locations each direction Toll zones between access locations Either paint stripe only or traffic channelizers
I-95, Miami Phase 2, open 2011 ETL, 2 lanes each direction (full time) Yes, to be determined Toll zones between access locations Traffic channelizers
I-680, Santa Clara Co., open 2011 1 concurrent lane each direction (part time) Separate ingress and egress with transition lanes Toll zones between access locations None, paint markings only
SR 237/I-880, open March 2012 1 lane each direction (part-time) None, however transition lanes are envisioned at the transitions to HOV on either end (TBD) Single toll zone Separate viaduct-barriers
I-495, Virginia 2 concurrent lanes each direction (full time) DARs only due to high anticipated weaving volumes Toll zones strategically located between DARs Traffic channelizers

Legend: ETL=Express toll lanes (all vehicles carry transponders) HOT=High-occupancy/toll lanes (HOVs free with min occupancy but they may be required to carry transponders) DAR=Direct-access ramp
Source: Parsons Brinckerhoff

6.3 Separation Treatments

The design of most managed lane projects is dominated by the access and physical separation issues from general-purpose lanes. The managed lane facilities currently in operation typically utilize either painted buffers or concrete barriers or pylons—also known as tubular markers or stanchions—to separate the priced lanes from the general-purpose lanes and designate entry and exit points. The earliest priced managed lane facilities implemented in the United States all featured continues concrete barriers. However, the success of the I-394 MnPass lanes which opened in 2005 and featured eight miles of painted buffers has led to several new projects that do not have solid buffers. For example, the I-35W managed lanes which opened in Minneapolis in 2010 use a near-continuous access policy, with skip striping to designate access, while the I-85 Express lane in Atlanta incorporates a camera-based “virtual barrier system” to discourage weaving.

The following sections focus on aspects of managed lane projects that are not likely to arise during the design of general-purpose highway lanes. Discussions of specialized signage and toll plaza requirements are also provided.

6.3.1 Concrete Barrier Separation

Physical barriers provide more positive access control and are more effective at reducing violations and maintaining premium traffic service; however, they can add significant cost to a project and may not be able to be accommodated within available right-of-way. Physical barriers may also pose safety hazards where intermediate access requires a break in a concrete barrier alignment. High-speed differentials between the general-purpose lanes and managed lanes often exist, and concrete barriers also help maintain a safe operation by preventing potential violators from inadvertently crossing into a non-barrier-separated managed lane and disrupting traffic flows. Continuous concrete barriers, such as Jersey barriers or moveable barrier systems, are a permanent and durable type of barrier and have been used for separation on a number of managed lane facilities around the country (Figure 6-12).

Figure 6-12: I-25 Express Denver Concrete Barrier Separation

A photograph of two lanes of interstate marked as toll separated by barrier from general lanes of congested traffic.
Source: Parsons Brinckerhoff

However, the presence of barriers is likely to increase response time for emergency vehicles accessing the managed lane. Concrete barriers can also complicate snow removal, unless sufficient storage reservoirs are provided in the shoulder. Exposed barrier ends at access points should also be buffered to protect motorists.

The installation of concrete barriers usually requires roadway modifications, as adequate shoulders next to each barrier alignment are needed. Based on AASHTO guidance, shows in Table 6 1, a minimum 4-foot shoulder is generally recommended between the managed lane and the barrier, while a 10-foot shoulder is usually preferred between the general-purpose lane and the barrier. [9] This guidance is shown in Figures 6-1, 6-2, and 6-3. Because of their right-of-way requirements, continuous concrete barriers are more costly to build than other separation options. As a result, most newer managed lanes projects do not use concrete barrier separation. However, barrier separation is commonly found on reversible lane projects that require positive separation due to oncoming traffic conditions.

Figure 6-13: Mountable Raised Curb Pylon Separation on the I-95 Express

A photograph showing orange pylons in a raised curb separation on interstate.
Source: Parsons Brinckerhoff

Figure 6-14: Individual Pylon Separation on the SR 91 Express Lanes

A photograph showing individual pylon separating lanes on interstate section.
Source: Parsons Brinckerhoff

Useful HOV Resources

Given the extremely close overlap between the physical design of managed and HOV lanes, those seeking detailed information on the physical design of managed lanes are directed to take advantage of the wealth of existing information on HOV design.

There are several excellent resources providing detailed information on the design of HOV lanes.

  • Guide for High Occupancy Vehicle (HOV) Facilities, American Association of State Highway and Transportation Officials: Washington, D.C., October 2004. Chapter 3 provides detailed design guidance for the implementation of HOV lanes, and by association, priced managed lanes.
  • High Occupancy Vehicle Planning and Design Guidelines, California Department of Transportation: Sacramento, CA 2003. The Caltrans HOV design guidance is contained within Chapter 3 of this publication; however, the Department has since updated the design in 2011 to reflect latest practices and experiences of facilities in California.
  • HOV Systems Manual, National Cooperative Highway Research Program (NCHRP) Report 414, Transportation Research Board, National Research Council, National Academy Press: Washington, D.C., 1998. Chapter 6 of the NCHRP report addresses design issues for managed lanes built within existing highways and in separate rights of way. The manual discusses the design features of barrier separated, concurrent flow, and contraflow managed lanes, as well as multiple access treatment. Sample cross-sections, signing and pavements markings are presented.
  • Fuhs, Charles A., High Occupancy Vehicle Facilities: A Planning, Operation, and Design Manual, New York: Parsons Brinckerhoff, December 1990. Also an industry standard, the Fuhs manual is organized in three main sections paralleling the decision making process for implementing managed lanes: planning, design, and operation. Among other areas, the design section provides comprehensive information on cross-section requirements for various configurations, enforcement, signing and pavement markings.

6.3.2 Pylon Separation

Tubular markers, also called pylons, channelizers, or stanchions, provide another separation option for buffer-separated managed lanes. These markers consist of a series of highly visible, reflective, lightweight plastic tubes that are approximately 3 feet in height, are placed at regular intervals, and cost $60 to $70 each. While they perform a greater psychological function than striping alone, they do not provide the physical protection of a concrete barrier. Their primary advantages are that they require less right-of-way than concrete barriers and are therefore less expensive. However, anecdotal experience from the SR 91 Express Lanes in Orange County and the I-95 Express Lanes in Miami indicate that 30 to 50 percent of the markers may need to be replaced within any given year, thereby increasing ongoing operations and maintenance expenditure as compared to barriers.

There are two primary types of tubular marker systems:

  • Pylons affixed to a mountable plastic raised curb (Figure 6-13); and
  • Individual plastic pylons attached to the roadway with adhesive Figure 6-14).

Pylons help distinguish the managed lanes and promote easier enforcement, but may not prevent errant buffer crossing and speed differential issues. They also allow emergency and maintenance vehicles to drive over them to take advantage of the higher travel speeds in the managed lane. Based on the experience of HOV and managed lane programs in California, 20-foot spacing between pylons is recommended. [10]

At some access transition zones in San Diego, pneumatically controlled or electronically operated pylons that retract into the ground have also been employed, but few such systems are anticipated in the future as they exhibit higher installation and maintenance costs.

Mountable curb markers feature a 10- to 12-inch-wide, 4-inch-high curb that supports vertical round or flat markers with reflective sheeting. The markers bounce back into place if they have been hit. The markers do not damage vehicles crossing them, but do make a loud banging noise. The mountable curb markers are designed to enable emergency vehicle access and to stand up under winter conditions. Although mountable curb markers are used by many highway departments to maintain traffic around construction sites, they have not been widely tested in high-speed lane separation situations.

Maintenance Issues

There are maintenance issues associated with all types of pylons. Experience shows that the displacement rate for traditional pylons is roughly 10 percent every 60 to 90 days, which means they have a limited life cycle and little opportunity to be repaired and. Although generally durable, the adhesive-mounted plastic pylons can only be hit a certain number of times before they cease to bounce back up. They can also be hit with such force that the units dislodge from the pavement. The New York Thruway Authority has used pre-drilled holes in the pavement to attach pylons in an effort to prevent pavement damage, but found the loss ratio to be the same as for the glued units. Dislodged plastic pylons also present a possible traffic hazard if they are displaced into the travel lanes and therefore add to traffic and liability risk. Similarly, the mountable curb pylons are often damaged on impact, but their replacement rate is 10 to 15 percent per year, which is less than for adhesive-mounted pylons. For both types, the plastic pylons tend to turn black in color from the tires of vehicles that strike them. The cost of the traditional pylons is approximately $45 (2011 dollars) per unit. Therefore, depending on spacing and frequency of replacement, both the capital and maintenance costs are high for tubular barriers. Moreover, retractable pylons require considerable maintenance to remove debris and provide for their operability. As with other systems they require replacement after a number of hits at a slightly greater cost (due to their design).

Snow removal is also an issue in many locations and presents two problems when pylons are used. As the snow is plowed, it is pushed into the adjacent lane because of the lack of a physical barrier. This means that the adjacent lane is not properly cleared. Also, snow removal equipment often damages pylons, either by plowing snow onto the posts or by hitting them.

6.3.3 Buffer Separation with At-Grade Access

The speed differential created often needs to be mitigated. Many HOV lanes dating from the 1990s have employed a painted buffer typically four feet in width to help promote driver sight distance. Buffers varying from a minimum of 1 to 4 feet (Orange County CA, Atlanta and Miami) to 15+ feet (I-10 Houston) have been implemented on about half the priced managed lanes. Other projects have opted to retain a single or dual solid stripe treatment without a designated buffer. Pavement marking separation is wider than standard and sometimes involves some overlap onto travel lanes on either side if space is limited. Solid stripes are employed to discourage buffer crossing except in designated areas. At-grade access may be provided in the form of a weave zone (Figure 6-4), weave lane (Figure 6-5), or a slip ramp (Figures 6-6 and 6-7). The advantages of buffer treatments are improved sight distance and more visibility to discourage buffer crossing where access is restricted. Disadvantages are the wider pavement section required and potential confusion if priced managed lanes are not operated full time.

Example projects include SR 167 in the Seattle area, I-680 in Alameda County, I-10 and I-110 in Los Angeles, I-85 in Atlanta and portions of I-394 and I-35W in Minneapolis.

Figure 6-15: Radio-Frequency Identification Reader Antennae

A photograph of two overhead readers mounted above the traveled way.
Source: Parsons Brinckerhoff

Figure 6-16: Different Windshield-Mounted Electronic Toll Collection Transponders

Two photographs of windshield mounted transponders.
Source: Parsons Brinckerhoff, Atkins Global

6.4 Tolling Provisions

6.4.1 Electronic Toll Collection Systems

Priced managed lanes rely on ETC systems for the collection and processing of toll payments. ETC keeps traffic flowing and benefits motorists by allowing them to pay tolls without having to stop at a toll booth and make a cash transaction. Most of the existing ETC systems in use today in the United States are based on radio-frequency identification (RFID) technology communicating in the 815 MHz frequency range. While no national interoperability standard has emerged, MAP-21 passed in July 2012 calls for all toll facilities on federal-aid highways to implement technologies and business practices that facilitate the interoperability of ETC systems. To date, the largest interoperable systems include EZ-Pass on the East Coast, Sun Pass in Florida, and FasTrak in California. ETC systems all utilize similar technologies that function generally as follows:

  • RFID antennas, with specially designed readers, are installed above tolling points on overhead gantries that span the specially designated toll lanes (Figure 6-15).
  • Vehicles equipped with a transponder or toll tag (Figure 6-16) pass under the antennas, and when detected, are interrogated by the reader to provide their unique transponder identification (ID) number.
  • The transponder ID is then stored locally in a roadside controller, along with a time stamp and other basic information like the lane number and the location/plaza ID. The controller is basically a rack-mounted computer with special software that is installed in a roadside cabinet and connected to the RFID readers in a local area network.
  • The roadside controllers, which are computer systems housed with a cabinet and including all necessary power, telecommunications, protection and storage to control lane equipment such as toll rate signs and communications components, periodically transmit the data that is gathered from the RFID antennas/readers to a back-office “host controller” via wide-area network (WAN). The WAN can use any combination of fiber optic, copper, or wireless communications and may rely on leased communications and the “cloud” to complete the connection between the lane and host computers.
  • The back-end host computer consists of several components that serve as a central database to manage accounts for toll payment, including an account management system that matches transponder transactions to registered user accounts and maintains the financial ledger.

Figure 6-17: Enforcement Cameras on the West Park Expressway in Houston

A photograph of an overhead truss with cameras mounted over the traveled way used in enforcement activities.
Source: Parsons Brinckerhoff

6.4.2 Violation Enforcement Systems

In addition to basic ETC components, most toll roads, and some managed lanes, also utilize photo-enforcement systems to increase accuracy and reduce the chance of missed transactions (Figure 6-17). Since RFID systems are susceptible to missed transactions due to a variety of environmental conditions, video enforcement is seen as a way to protect revenue streams and ensure that close to 100 percent of all trips on the toll road result in a paid transaction.

While the basic components of a video toll/violation enforcement system are the same, there is no single national standard today for processing violation images, although at least one organization (the Alliance for Toll Interoperability) is now espousing the concept of a central clearinghouse for all North American toll roads. The basic components of a video toll/violation enforcement system are as follows:

  • Photo-enforcement cameras, with built-in or external triggers and lights, are installed above tolling points on overhead gantries that span the specially designated toll lanes.
  • Vehicles equipped with license plates pass under the cameras in a “transaction envelope,” and when triggered, the cameras photograph the license plate and store one or more image(s) of the license plate.
  • The license plate images are then stored locally in a roadside controller, along with a time stamp and other basic information like the lane number and the location/plaza ID. The violation image controller is connected to the camera(s) via the local area network, and is usually a separate computer than the toll controller but can be mounted in the same roadside enclosure.
  • The violation image controllers periodically transmit the image data to the back-office host computer via the WAN. More bandwidth is usually needed to transmit the larger image files than the text-only toll transaction data.
  • The back-end computer consists of a violation processing module that contains image review software and an automatic license plate recognition (ALPR) function. ALPR uses optical character recognition algorithms to convert image data into text, using license plate character patterns based on certain confidence levels of the software. In general, between 80-90 percent of all images can be converted to text with ALPR, although most agencies require humans to review each image before issuing a violation notice to the offender.
  • A violation noticing application is usually included in the software to handle the citation process and to track resolution of the violation through payment or dismissal. Violation payments are reconciled with the same account management system as the primary toll accounts.

When administered proactively, ALPR serves as a primary means of “pay by plate” in which toll invoices are mailed to vehicle owners, thereby eliminating the requirement that a motorist carry a transponder. However, “pay by plate” is a more expensive method of toll collection for administration purposes, and is often accompanied by an administrative surcharge. Additionally, the use of ALPR in managed lanes is still questionable, in that only one facility nationwide has begun to require eligible HOVs to register their license plate, thus making it impossible to ascertain the vehicle’s occupancy status from the license plate image alone. Other strategies to mitigate this limitation are beginning to emerge and include carpool registration, switchable transponders, that allow the driver to declare the number of occupants in the vehicle, among other means.

6.4.3 Requirements for Variable Pricing

The use of variable pricing on priced managed lanes requires additional infrastructure and communications abilities. Since pricing is used to maintain a specified operational threshold, the toll system needs to either be based on a schedule that reflects typical peak demand curves, or it needs to be dynamic and receive real-time traffic input to calculate the toll rate. This real-time traffic information is obtained using loop detectors or other devices capable of detecting characteristics such as traffic volume and speed. A tolling algorithm then uses these characteristics to calculate the appropriate toll to charge. The toll can be raised or lowered in response to traffic conditions as appropriate to influence managed lane operations. However, business rules need to advise customers of the prevailing toll rate. This is typically done upstream of entry points using dynamic signing elements in accordance with guidance found in the 2009 MUTCD. The prevailing price a customer sees when making a choice to use the lane should be guaranteed once they enter. For this reason, the tolling system design opens a customer transaction envelope at the first toll point, but does not process the completed trip transaction until the vehicle passes one or more downstream tolling gantries and the transaction is closed.

6.4.4 Typical Toll Zone Design

Priced managed lane toll zones will be equipped with all necessary infrastructure to identify vehicles, process toll transactions, identify and photograph license plates of potential violators, and inform enforcement personnel as to account status through strategically placed beacons. In the typical toll zone configuration, a vertical post with counter-balanced cantilevered horizontal arms will serve as the toll gantry (see Figure 6-18). In this system, a minimum of 18-foot vertical clearance will be provided between the automated vehicle identification antenna, the transponder reader, and rear-plate-facing license plate image camera on the mast arm. A transaction status indicator beacon will be mounted on the column supporting the toll collection gantry, approximately seven feet from the roadway surface. Many toll zones will also have a designated area for adjacent enforcement personnel monitoring. The availability and placement of these observation locations will generally be in the vicinity of the toll reader and beacons. Sufficient lighting will be present to support license plate recognition and image capture, as well as safety for structural illumination.

All of the priced managed lane toll zone components need regular access for preventative maintenance and other in-field connectivity. To provide this access, all components should be housed collectively in hardened and protected utility cabinets with sufficient controls to prevent tampering, preserve safety for maintenance personnel, and provide easy access. It is preferable that these cabinets be placed as far as possible from the travelway and beyond the clear zone. The cabinet must have an access door and be located within 200 feet of the gantry post. Sufficient conduits underneath the general-purpose lanes must be installed to the gantries.

Figure 6-18: Typical Managed Lane Toll Zone Design

A graphical representation of a typical managed lane toll zone design showing three traveled lanes and on the left a 2 foot buffer and to the left of that the express lane.  The graphic shows the overhead and roadside equipment for tolling.
Source: Parsons Brinckerhoff

6.5 Signage

Accurate, informative signs are essential in explaining operational procedures of managed lane facilities and ensuring safe access and egress from the managed lanes. Managed lane signs should provide motorists with information on the following:

  • Access and egress locations
  • Distances to ramps
  • Occupancy requirements
  • Operating hours
  • Cost
  • Enforcement issues

In addition, motorists need to be given adequate time to decide whether or not to use the managed lane facility and then be able to access the facility safely. This requires that the proper information be provided so that motorists are able to make informed, real-time decisions on whether or not to use the facility.

Signage for managed lanes should generally adhere to the standards prescribed for special-use facilities in the federal Manual on Uniform Traffic Control Devices (2009 edition) Section 2B-49 and 50.

Figure 6-19: Variable Message Sign on the I-95 Express in Miami

A photograph of an overhead variable message sign indicated the cost for traveling on the roadway with a message of registered carpools free.
Source: Parsons Brinckerhoff

6.5.1 Access and Egress Signage

Good signage is critical to directing motorists to access and egress locations on barrier-separated facilities. In order to access interchanges, the corresponding buffer opening must be placed several thousand feet upstream of the exit ramp. Drivers need to be directed to the buffer openings providing access to their desired interchange. The sequence of signs for access to managed lanes is provided in the 2009 MUTCD.

6.5.2 Variable Message Signs

Managed lane signage systems must also provide motorists with information on toll levels. Good signage is particularly important when variable tolls are involved. These can involve either time-of-day tolls or a dynamic pricing system that changes price according to the level of congestion in the parallel general-purpose lanes and/or the availability of excess capacity on the managed lane(s).

When this is the case, variable message signs are the best way to provide motorists with accurate and current information. Variable message signs can also provide motorists with other information, such as general travel conditions, and enforcement policies. [11] When variable or dynamic pricing is used, at least one variable message sign should be placed before all entrance points to the managed lane in order to provide drivers with the basic information they need in order to determine whether or not they will use the facility. In addition, the outermost entrance locations or those spaced more than two miles apart may warrant the placement of two or more variable message signs that display the toll rate information so users have sufficient time to make a decision about whether or not to use the HOT lane. These signs operate in parallel and are usually controlled from an operations or traffic control center. Figure 6-19 shows a variable message sign providing toll rate information to specific destinations on the I-95 Express in Miami. Chapter 2G of the 2009 MUTCD provides comprehensive information on managed lane signage. [12] In particular Figures 2G-21 through 2G-24 in the 2009 MUTCD show examples of the sequence of guide signs for various configurations of initial and intermediate entrances to priced managed lanes.

Figure 6-20: Enforcement Area on I-45 in Houston

A photograph of enforcement officers monitoring traffic and identifying unauthorized vehicles where two motorcycle officers sit in the shoulder lane watching vehicles enter the managed lane.
Source: Parsons Brinckerhoff

6.6 Enforcement Areas

Managed lane facilities should also include locations from which enforcement officers can monitor traffic and identify unauthorized vehicles. In order to see occupants properly during hours of darkness or inclement weather, lighting is required at observation points. The enforcement areas should be large enough to accommodate the need for enforcement officers to accelerate to the speed limit before entering traffic. The areas should be wide enough to accommodate safety enforcement action and may be located near tolling points, allowing officers to monitor traffic as it enters the facility and provide a visual deterrent to would be offenders (Figure 6-20). Barrier-separated facilities will require less enforcement presence than would be required for a roadway that is not physically separated.

The primary reason that facilities for on-site enforcement are recommended near the access points is that current technologies—both video and thermal—cannot accurately discern the number of occupants in large numbers of vehicles traveling at highway speeds. Moreover, the presence of an officer is a useful deterrent for misuse by those who want to abuse the system. Enforcement issues are addressed in further detail in Section 7.3.


[8] HOV Guidelines for Planning, Design, and Operations, Traffic Operations Policy Directive, California Department of Transportation, April 2011. Back to reference 8.

[9] AASHTO, Guide for High Occupancy Vehicle Facilities, 2004. Back to reference 9.

[10] High Occupancy Vehicle Facilities: A Planning, Operation, and Design Manual, Parsons Brinckerhoff, 1990. Back to reference 10.

[11] HOT lane operators have contemplated displaying anticipated travel times savings together with toll levels in order to help motorists make the decision whether or not to use the HOT lane, but have generally decided against this, given that the actual time savings experienced by motorists could differ. Back to reference 11.

[12] Back to reference 12.

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