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Chapter 6
Operational Issues

As tolled facilities, HOT lanes have a number of operational needs – such as toll collection and enforcement – that are not normally associated with general-purpose or HOV highway facilities. This chapter provides information on the different operational aspects for which HOT lane operators are normally responsible, with the exception of public outreach, which is addressed in Chapter 4.

Lane Management

As with HOV lanes, HOT lane traffic levels need to be limited to volumes that ensure reliable speed advantages when adjacent general-purpose lanes are congested. Without this type of management the HOT lane facilities also risk becoming congested and losing their benefits. Two issues are critical in lane management:

These issues are discussed in the following sections.

Maximum Capacity Versus Managed Capacity
Various references provide an understanding of highway lane capacity. This capacity is based on the maximum flow that can be expected to occur under the prevailing conditions. As volume increases, speed gradually decreases until reaching a point of instability typically between 2000 and 2100 vehicles per lane per hour. When throughput degrades beyond maximum capacity, speeds decline to levels around 15 miles per hour and flows drop as low as 1300 vehicles per lane per hour. Analysis of speed-flow data on congested highways in greater Los Angeles using the Caltrans Performance Measurement System in September 2000 suggests that contrary to the Highway Capacity Manual range of 35-50 mph, 60 mph is the optimal rush hour speed facilitating the highest throughput levels.19

When lanes are managed to promote “free flow” conditions, as is the case for HOT lanes, throughput must be contained to a level below maximum capacity. This regulated threshold, or managed capacity, is simply a management benchmark that ensures premium traffic service for HOT lane users.

Much like the design and operational variables identified in the Highway Capacity Manual, managed capacity levels may vary from one HOT facility to another depending on the number of access points, vehicle mix, roadway slope and configuration, separation treatments, and number of travel lanes. A single HOT lane will have a lower managed capacity than multiple HOT lanes. For example, flows on the Houston I-10 Katy Freeway QuickRide – a one lane, reversible-flow facility are kept to 1500 vehicles/hour. However, the SR 91 Express Lanes – which provide two travel lanes in each direction – have been able to operate at acceptable conditions with flow rates of 1800 vehicles/hour/lane.

A safe range for establishing managed capacity for most project settings would be approximately 1700 hourly automobile equivalents per lane, with the understanding that road configuration, slopes and speed limits can drive this number up or down. This threshold is reflected in a number of HOV references and locally adopted policies, and is also appropriate for HOT lanes. Local traffic studies can be used to identify more precise, site-specific capacity levels. This may also be accomplished by studying the effects of allowing small numbers of additional onto the managed lanes in order to identify an optimal managed capacity.

Traffic Models Validate the Operational Benefits of HOT lanes

A recent UCLA Ph.D. dissertation by Eugene Kim provides new and important quantitative analysis of HOT lanes. The study, HOT lanes: A Comparative Evaluation of Costs, Benefits, and Performance uses a logit travel-demand model to compare changes in travel times associated with the conversion of an existing HOV lane in a congested corridor to:

  • a general purpose lane;
  • a HOT lane; or,
  • a toll lane.

Kim’s research finds that in almost all cases, HOT lanes or toll lanes provide greater fiscal and mobility benefits. Conversion to general purpose lanes is only defensible when HOV use is less than 7 percent of all corridor trips and when there are fewer than 700 vehicles per hour in an HOV lane. Otherwise, the implementation of tolls on HOV lanes produces greater benefits because tolling preserves free-flow conditions on the managed facility, even if congestion worsens on the general purpose lanes. Kim’s modeling work also demonstrated that either tolling option would produce large delay reduction benefits regardless of whether the conversion results in a significant increase or decrease in the proportion of HOVs. Similarly, Kim’s research finds that in terms of air quality the HOV base case would produce greater output of toxins such as NOx and CO than conversion to either general purpose or toll lanes. However, toll lanes would produce the largest reduction in emissions because they eliminate vehicle trips and reduce congestion more effectively compared with general purpose lanes.

Kim’s research corroborates speed flow analyses and other traffic performance and air quality studies conducted around the country.

This description of Kim’s findings is based on a summary appearing in “Reason Surface Transportation Innovations Newsletter #4,” Reason Institute, August 6, 2002.

It is important to understand that for any HOT lane to be successful, the facility must be regulated at a managed level that is well below the maximum capacity cited in the Highway Capacity Manual. As described above, the operators of projects including I-15 FasTrak have taken steps to open the lanes gradually to more over time, in order to insure that the HOT lanes do not become congested. This conservative approach enabled the HOT concept to gain public credibility before attempting to maximize the number of users.

Management Tools
While the role of lane management in preserving HOT lane benefits is evident, the actual application of management techniques can be complex and dynamic. Although much attention focused on the role that pricing can play in regulating lane demand, pricing is only one of a number of management policies that can be used with HOT lanes. The following three tools are used to maintain superior traffic service levels on HOT lane facilities:

Applied in combination, these tools give the operating agency a wide range of opportunities to flexibly adjust demand conditions to meet available lane capacity. Traffic service conditions need to be monitored on an on-going basis to determine whether pricing structures are meeting the performance goals (e.g., traffic service, customer satisfaction) established for the facility.

The Conversion of HOV Facilities to HOT Operations
At present, approximately 70 percent of the nation's HOV lane miles operate with peak hour volumes of between 900 and 1500 vehicles/hour. Ten to 15 percent are operating with over 1500 peak hour vehicles, and the remaining 10 to 15 percent below 900 vehicles in peak hours. This suggests that there is some available capacity to allow other user groups on certain HOV facilities. However, residual capacity is quite limited and additional traffic levels would need to be managed closely.

Changes in occupancy regulations on HOV facilities can alter utilization levels and result in additional capacity becoming available for possible use by non-HOV vehicles. Occupancy requirements are set at 2+ on approximately 95 percent of all lane miles operated in the United States. An increase to HOV 3+ operation can be expected to lower traffic levels dramatically, making an HOV 2 or SOV possible, as was the case with the Katy Freeway in Houston.

Access to HOV lanes is either continuous or at designated locations. About half the nation's lane miles restrict access to designated locations. An access designation threshold is typically not less than every 2-3 miles. Few of these sites with restricted access have changed access yet to make lanes more restrictive when volumes reach capacity. This is one tool that may be used more in the future.

An Ongoing Process
The role of operations management is critical to successful HOT lane performance. The role relies on a fundamental understanding of the facility’s available vehicle carrying capacity under varying conditions, and an understanding of how various management tools can be employed in combination to achieve reliable “free flow” conditions while optimizing utilization. This balancing process can be extremely dynamic, changing when incidents occur and as demand builds and falls in each successive peak period. The ability to manage a HOT lane requires an ongoing monitoring presence and ability to aggressively react to conditions that adversely affect roadway performance. Without this complement of operations presence, a HOT lane is unlikely to meet its objectives in commute periods when it is most needed and justified.

Management Measures on Two Existing HOT Facilities

On the I-15 reversible lanes in San Diego, pricing, access and eligibility all play roles in lane management. Access is limited to a single set of ingress and egress ramps with the project functioning as a pipeline. No intermediate access is provided, so mainline demand cannot be overwhelmed by too many entering vehicles. HOVs with two or more persons are given a free trip to encourage carpool formation and transit use, and others are priced. Pricing varies significantly between peak and off-peak conditions to help regulate demand. Collectively, these strategies ensure that the I-15 project provides a high-speed, reliable trip to users.

On the I-10 Katy Freeway in Houston, a single reversible lane with more limited capacity than I-15 contains about five ingress and egress locations along a 12-mile distance. The potential to overload the lane exists with this many access points. The Katy HOV lane exceeded capacity during peak hours with 2+ occupant carpools and transit, so eligibility rules were raised during these isolated peak periods to 3+. The residual capacity left by removing many of the carpools was ultimately provided to 2-occupant carpools for a price that is fixed per trip. With a very limited lane capacity the potential for dynamic pricing is not critical to managing demand on this facility, but restricting use to a smaller potential priced market was. This approach successfully ensures that as many vehicles as possible can still travel in the lane during periods of greatest demand.

Toll Collection and Registry Procedures

Pilot Period Monthly Permits

During pilot test periods, monthly permits may be issued to a select group of motorists. While this approach does present certain enforcement challenges, the permit system is low in cost and easy to implement. In both Houston and San Diego, HOT lane operations were first implemented on test basis in order to determine whether they would achieve the desired effects on traffic operations and also win the acceptance of the public. As such, it was important to minimize the upfront costs, so rather than relying on expensive electronic toll collection equipment, HOT lane users were issued monthly permits that they displayed on their vehicles. The permits are generally hang-tags or stickers that can be mailed to participating motorists who then display them on their windshields when using the HOT lane. The hang-tags or stickers need to be visible for enforcement purposes, but should not obstruct the driver’s view.20

Although test programs relying on monthly passes are relatively simple to implement, they have a downside in that they involve selling a month of unlimited trips and cannot sell single trips in the same way that that ETC technologies can. When equipped with an ETC transponder, motorists are able to make discriminating decisions about when to pay for the premium travel conditions the HOT lanes provide.

Automated Variable Priced Toll Collection

If HOT lane operations are maintained on a permanent basis, it is best to automate toll collection. The equipment requirements and technical functions of automated toll collection systems are described earlier in Section 4.2.

A protocol for distributing transponders to customers needs to be established, together with a financial/accounting system to reconcile patron accounts as well as toll payments attributed to other agencies where reciprocity has been established for toll payments. These functions, whether facilitated by public or private agency, could be performed by that agency or potentially outsourced.

Issuing Transponders
Generally motorists order transponders by telephone or over the Internet. In certain cases they are also available at a customer service center (Figure 22). Payment policies also need to be established, and operating agencies may find it to their advantage to require users to pay via credit or debit cards rather than cash. Similarly, HOT lane operators will also need to determine whether or not motorists should be required to pay a fee to obtain the transponder itself.

Figure 22.
I-15 FasTrak Service Center

This photograph shows the entrance to the I-15 FasTrak Service Center located in a shopping center in San Diego, California.

In certain cases, HOT lane operators may use a region-wide automated toll collection system. If this is the case, the agency will need to adhere to the distribution policies and window placement guidelines established by the regional consortium of tolling agencies that use the technology.

Registry Procedures
Given that all tolls are collected electronically and involve no cash transactions, internal accounting procedures for HOT lanes are simpler than those required by traditional toll facilities. The computer systems and software running the ETC equipment are also capable of instigating credit card transactions, generating bills, and generating detailed reports allowing agency officials to track all financial activity.

If the HOT lane operator is participating in a region-wide automated toll collection system, the facility will be assigned a use code that will be included in all transactions in order to distinguish it from other tolled facilities.

This is the case in Orange County in particular, as well as Houston, both of which operate a HOT lane facility in addition to regional tollroads. Both types of facilities share the same transponder technology, same accounting database, and same outlets for purchasing and subscribing to the various programs (although there are some unique exceptions to this at each locale). Recent experience shows that use of HOT lanes is made more convenient if the transponders for a project are the same as for other toll facilities in a given locale or region.


Enforcement procedures need to be established for HOT lane facilities to ensure that motorists comply with both occupancy and toll policies.21 Given that toll collection on HOT facilities is electronic, some violations may be unintentional as unfamiliar motorists might expect to be able to make a cash payment at a manned toll booth and then be unable to exit due to the presence of barrier systems. Equipment malfunctions could result in nonpayment by regular users who have every intention of paying the prescribed toll. Nonetheless, drivers can also avoid payment intentionally, such as using tags reserved for vehicles paying lower tolls (i.e., HOVs), shielding the transponder, or using the HOT lane without a tag.

Consistent signage and police presence should convey the message to motorists that the likelihood of being cited for violations is high. It is especially important to educate motorists during the first days of operation and then to continue reinforcing the message.22 One of the most effective techniques is to install signage that explains the use of video enforcement techniques. Visible and consistent police presence near tolling points further reduces the likelihood of violations and deters motorists from fraudulent activity, the use of the wrong tag, or the opportunity to “evade the toll”. Violators are also less likely to enter a HOT facility if there are limited opportunities to escape and if the perception of being caught is high.

At the operational level, enforcement can be implemented using several different surveillance and detection procedures. The methods chosen depend on several factors including the nature of violations police are trying to address and the physical characteristics of the corridor. Enforcement personnel should provide input during the planning and design of HOT lane facilities in order to optimize their ability to patrol them once they become operational.

Enforcement Techniques and Procedures

Toll Collection
Given their strong dependence on automated toll collection systems, the enforcement of toll infractions on HOT lanes also relies heavily on those same systems. The general trend in enforcing toll collection on HOT lanes and other facilities using ETC technologies is video surveillance. This approach involves the use of in-lane toll violation cameras at tolling points, which are integrated with other ETC systems and triggered when incomplete or anomalous transactions occur. This is a highly effective, cost-efficient, and non-intrusive method (Figure 23).23 Repeat offenders are generally subject to legal action, as are those who shun payment. Special state legislation is normally required before automated video surveillance enforcement methods can be put in place. Legislation is also likely to be needed to provide access to Department of Motor Vehicle records.

Figure 23.

This is a photograph of a violation detection camera at an electronic tolling location.  The camera is used to identify vehicles when the violation of a business rule is detected.

Occupancy Requirements
Given the limitations of automated technologies and the difficulties of verifying the number of occupants in a vehicle, the enforcement of occupancy requirements requires routine visual inspection. Several challenges are involved including vehicle design, tinted windows, inclement weather, limited lighting, lack of enforcement locations, and small occupants such as children and infants who may not be clearly visible to outside observers. Enforcement officers generally park adjacent to the lanes and stand outside their vehicles to have a better view of the approaching vehicles. This approach can be effective, but can increase congestion especially if more than one patrol vehicle is involved. A physical inspection of suspected occupancy violators has proven an effective enforcement technique on the I-15 in San Diego.

Given the difficulty and associated delays of stopping violating vehicles while they are traveling on barrier-separated facilities, traffic citations are generally sent by mail to owners of violating vehicles. This practice generally requires specific state legislation and has been an effective tool in addressing HOV violations.24

Automated Violations Processing

When video enforcement is used on facilities such as the E-470 EXPRESS Lanes in Denver Colorado or the Port Authority of New York and New Jersey’s bridge and tunnel crossings, a Violation Processing Center (VPC) is established to process transactions. An investigation into a potential violation is triggered by when the violation of a business rule is detected. This could involve a mismatch between tag class and AVC class; a vehicle entering with no tag; a vehicle using a lost, stolen or otherwise invalid tag. In such a case, the ETC systems communicate in real time with in-lane toll violation cameras that capture an image of the license plate of the suspect vehicle. The image and other information related to the anomalous transaction are then transmitted digitally over a secure fiber optic backbone from the lane to a local computer, and then on to a violation host computer at the VPC which receives similar information from all tolling points. Here each image linked to a transaction is viewed for clarity and checked against a list of a registered program subscribers before an invoice for the toll and administrative fee is mailed to the violator. Department of Motor Vehicle records are used to verify the name and addresses of the registered owners of the violating vehicles, and reciprocity agreements are often put into places among state using compatible ETC systems to obtain information on out-of-state vehicles. Violations processing is covered by legislative action which generally is based on tort offense (as opposed to a motor vehicle violation) and is linked to a person’s ability to renew his or her license registration if the violation is not paid. It also allows court intervention. Violators generally receive a warning/fine (toll + administrative fee) through the mail containing the picture with the date, time and location of the violation.

Pilot Programs
There are different enforcement issues when considering pilot projects involving monthly permits. In such cases enforcement relies only on visual identification, with officers searching for a decal or placard on the vehicles using the HOT lane and determining the vehicle occupancy of those not displaying passes. This complicates the split-second decision-making process confronting enforcement officers and allows only for random challenges much like looking for out of date motor vehicle tag registrations.


Penalties for violations must be adequate to discourage the willful violator such that reliance on dedicated enforcement officers can be minimized. Penalties on HOT/HOV projects in the United States vary from $40 to over $310 ($100 plus court costs) for the first offense. In California, HOV penalties become rather steep after the third offense, rising to over $1000 inclusive of court costs.

Signs should be posted indicating fines for violations and that police are enforcing the facility. Empirical evidence suggests that when fines are sufficiently high, observed violations for such offenses may be reduced significantly.

Performance and Monitoring
A systematic monitoring program is required to determine compliance levels and provide a basis for fine-tuning HOT operations and enforcement requirements. Funding to support enforcement activities should include a contractual arrangement for reporting requirements from the enforcement agencies. The data in these reports would be of great benefit for future planning and for identifying resource requirements for ongoing enforcement and future HOT projects.

Helpful performance monitoring information includes:

This information can be used to correlate the level of police efforts with compliance in a corridor and provides information that can be used to fine-tune enforcement activities.

Incident Management

Incident management is critical on HOT lanes. The need for effective management is two-fold:

Because of these realities, real-time traffic sensing and surveillance equipment should be used to monitor travel conditions on the HOT lane facility at all times, with the proper authorities notified whenever there is a severe deterioration in speeds or traffic service. Incidents should be reported to response agencies within minutes of their occurrence. In addition to the right technology, quick detection also depends upon observant staff.

The major difference on a HOT lane when an incident occurs is normally the limited access points. The site, depending on the incident (fire, injuries), can often be reached from other lanes more easily than from the actual HOT lane. Protocols for responding to different types of incidents should be established in advance, with appropriate training provided to all response personnel. On-scene traffic control is also critical in maintaining traffic flows on other lanes and allowing tow truck and rescue vehicles to access the actual incident location if necessary. Tow trucks and rescue vehicles are typically brought in from the opposite direction of traffic if the lanes are completely blocked. Attempts should be made to keep at least part of the facility open to allow inbound response agencies to reach the incident depending on the magnitude, type and location of an incident as well as the physical constraints of the facility.

Plans and Procedures
Response training should include the criteria for use, procedures for getting messages posted, and the process for activating and deactivating messages. Incident Response Plans and Emergency Procedures including drills must be prepared in concert with all response agencies to cover various types of incidents including accidents, breakdowns, snow/ice control, other routine maintenance, and major occurrences, such as an evacuation or special event. Plans also need to be developed to close HOT facilities to traffic in the event of certain incidents.

Typical Incident Response Plan Issues

  • Maximizing response to blocking incidents
  • Establishing emergency vehicle alternate access routes when lanes are altered or closed
  • Providing advanced incident response training for all responders
  • Conducting at least one training exercise to test the incident response plan
  • Providing the briefing to the media and seek their support for more frequent traffic reports
  • Maintaining a liaison role with the key response agencies throughout all phases of construction
  • Developing and maintaining a comprehensive list of all key project personnel including emergency numbers
  • Identifying alternative routes
  • Providing public notifications thru the National Transportation Safety Board’s (NTSB) Highway Accident Report (HAR); news media; agency; project or traffic websites

Additional Construction Period Incident Response Issues

  • Implementing 24 hour stationary or roving service patrols in the construction zone
  • Creating temporary collision investigation/enforcement sites within the construction zone
  • Establishing the construction zone as an immediate tow area
  • Developing agreements with the construction companies to use their heavy equipment to assist in clearance of debris from truck accidents
  • Identifying landing locations for medical response helicopters near the construction zone
  • Offering presentations to key stakeholders such as the trucking industry, major employers and automobile clubs before construction starts
  • Installing surveillance throughout the construction area to detect an incident and monitor traffic flows


HOT lane operations require the maintenance of the roadway, including the pylons or barriers, signing and markings, and electronic toll devices and infrastructure. Maintenance activities are also likely to include repair, rehabilitation and replacement of equipment, pavement, shoulders, signs, barriers, pylons and markings. Each component requires an assessment of how often maintenance should be performed and when major replacements or rehabilitation are required so that funding may be reserved.

It is also important to consider the initial capital costs for equipment, signage and ETC equipment, as well as equipment for snow and ice removal in colder climates.

If the facility is to be privately owned and operated, then a maintenance fleet may need to be assembled, housed and maintained separate from the state DOT, specifically for the HOT lane. Alternatively, a private owner may contract with a state DOT or public tollroad operator for maintenance, in which case the agency may need to augment its maintenance fleet for that facility. Even if it is state owned and operated, there is always the potential need for additional maintenance vehicles and personnel.

19 Freeway Performance Measurement Project, University of California at Berkeley, Partners for Advanced Transit and Highways, Caltrans, September 2000. http://pems.eecs.berkeley.edu/login.phtml

20 A similar approach was followed on the now defunct Connecticut Turnpike in the 1950’s and 60’s. Instead of a tag, a license plate was affixed to the front of the vehicle. Similarly the Delaware River Port Authority (DRPA), which for years used a monthly “Bar Coded” system enabling holders to pay a much lower toll in automated lanes if they used the DRPA bridges more often in a given month.

21 With the proper systems in place, the enforcement of HOT lane facilities should be no more difficult than that of HOV facilities. Given that HOT facilities provide SOV motorists with a legal option for obtaining faster trips, HOT lanes may actually reduce the temptation to violate.

22 Seattle routinely uses a special motorcycle enforcement squad for the first six months of any HOV project operation.

23 Legislation may be required in order to use cameras for law enforcement purposes in certain locations. Fixed, single-frame toll violation cameras should not be confused with video surveillance systems that use steereable moving picture cameras to survey larger areas in order to monitor traffic conditions and detect incidents.

24 In Virginia, where citations are sent by mail if an enforcement officer visually documents an HOV occupancy violation, there has been a ten-fold increase in the number of citations issued and a corresponding reduction in violations.

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