High occupancy toll (HOT) lanes are a type of managed lane reserved for single-occupant vehicles that pay a toll and high-occupancy vehicles (HOV) that access the lane for free. HOT lanes use electronic tolling and variable pricing to manage demand in the lanes in order to maintain a speed advantage over the adjacent general purpose freeway lanes.
High occupancy toll (HOT) lanes are a complementary strategy to high-occupancy vehicle (HOV) lanes and tolling. Their purpose is to help reduce congestion and provide incentives for higher occupancy vehicles. HOT lanes function as special freeway lanes reserved for single-occupant vehicles that pay a toll while HOV users can access the lane for free. Unlike bridge tolls or toll roads, HOT lanes are optional. Drivers who don’t want to pay a toll can still use the regular lanes for free.
Most HOT lanes are converted or expanded HOV lanes, adjacent to general-purpose freeway lanes. They are equipped with electronic tolling infrastructure to allow single- or low-occupancy vehicles to pay a toll to access it. In order to maintain the HOT lane’s speed advantage over the general purpose lanes, agencies continuously adjust the toll to keep the lane from becoming congested. Agencies also typically do not allow trucks over a certain weight to access the lanes so that speeds can be maintained.
Agencies increasingly view HOT lanes as an attractive managed lanes strategy because it can both encourage carpooling (via the HOV component) and generate revenue. Agencies often use these funds for roadway improvements, transit enhancements, or other transportation investments in the corridor.
Time of day usage
During peak commuting hours, HOT lane tolls are typically much higher than during other hours of the day. Agencies can also adjust the minimum occupancy requirements to qualify as an HOV, to give preference to especially efficient vehicles, such as vanpools and buses. Some agencies, including WSDOT, charge tolls only during certain hours of the day, when congestion levels warrant it. During the remainder of the day, the HOT lanes are made free to all. In the case of accidents blocking lanes or other significant disruptions on the regular lanes, agencies typically open the HOT lanes to all vehicles.
Equipment and infrastructure
Most HOT lanes require that all vehicles using the lanes have a registered transponder affixed to the windshield. These small, wireless devices are used to associate vehicles to registered users in the toll account system. Transponders are sometimes equipped with a switch for the driver to indicate the number of passengers in the car.
Tolling equipment installed along the HOT lane registers when a vehicle enters and exits the lanes and, if a toll is required, charges the associated account holder. Variable message signs (VMS) are used in advance of the entrances to the HOT lanes to notify drivers of the current toll. VMS may also be used to display travel time comparisons between the HOT lanes and general purpose lanes so drivers can determine whether the toll is worth it.
Video and automated license plate readers are used to identify vehicles without registered, functioning transponders, so that the owners can be sent a warning or fine.
The main areas of enforcement are around vehicles that falsely claim HOV status (e.g., by switching transponder to HOV when they are a solo driver) or vehicles that enter or exit the HOT lanes illegally to avoid detection by the roadside electronic toll readers. Enforcement is conducted primarily by visual observations from highway patrol. Many agencies are currently evaluating automated vehicle occupancy detection technology, but it is not currently reliable enough for widespread deployment.
Toll rates and access considerations
In stretches of roadway that have very high travel demand, the toll price that agencies need to charge in order to maintain acceptable speeds (typically at least 45 mph) can rise to very high levels. Virginia’s I-66 Express Lanes, which connect Northern Virginia to Washington, D.C., regularly exceeds $35 during the morning peak for the 10-mile stretch (1). There is no cap on tolls, which allows the price to adjust as needed to manage demand. However, dramatic surges in toll pricing have also led to public and political debate about the fairness of this practice.
Other HOT lane installations, such as the I-10 and I-110 Express Lanes in Los Angeles, cap the per-mile toll rate. During peak periods, toll rates regularly rise to and sustain at the maximum rate, suggesting that the posted price is not fully reflective of demand. As a result, speeds in the HOT lanes are not much better than in the general purpose lanes.
Some HOT lanes exempt certain vehicle types, like motorcycles and low- and zero-emission vehicles, from tolls. In some regions, such as Los Angeles and the San Francisco Bay Area, where electric vehicles are very popular, this has led to crowding in the HOT lanes, and speeds have suffered because increasing the toll does not act as a deterrent. Agencies in both these regions have since removed the toll exemptions for these vehicles (2).
When to use this strategy
HOT lane conversions make sense for freeways with existing HOV lanes that are not fully utilized (i.e., could accommodate higher vehicle volumes while still maintaining adequate speeds). HOT lane conversion and expansion to two lanes is often done during freeway widenings in place of or in addition to adding general purpose lanes.
Agencies seeking to address funding issues may consider HOT lanes as a way to implement freeway improvements while covering capital costs, operating expenses, or funding additional transportation improvements in a corridor, including transit service.
- Improved travel time and reliability for HOV and single-occupant vehicles that are willing to pay a toll
- More efficient use of existing roadway infrastructure
- New revenue potential to fund transportation improvements
- Lower cost alternative to constructing new general purpose lanes
What you need in order to implement
- Regional policies on managed lanes, including HOT lanes, to identify the regional transportation vision, the goals and objectives for the specific corridor, the primary purpose of the proposed HOT lane, and what role revenue expectations play
- Analysis of current congestion levels, traffic composition, and physical roadway characteristics to evaluate the benefit of HOT lane conversion and determine an appropriate tolling approach
- Extensive media and public outreach to provide education to users, given that HOT lanes are new to most travelers and introduce a payment requirement that may have not existed before
- Inter-agency coordination to develop policy, operations, and communications for HOT lanes and tolling strategies across jurisdictions and/or systems
- Law enforcement coordination to ensure driver compliance and to address potential violations
- Electronic toll equipment, including vehicle transponders and roadside vehicle detection equipment, to identify eligible vehicles entering and exiting the HOT lanes
- Traffic detection to monitor traffic speeds and volumes in the general purpose lanes and the HOT lanes to trigger demand-based toll price changes
- Back office systems to process payments and assess fines
- Automated license plate readers and CCTV video detection to identify vehicles accessing the HOT lanes improperly
- Variable message signs to post current toll rates and display traveler information messages
- Regular testing and validation of the HOT lane system to confirm that all components are operating reliably and safely
- Continuous re-analysis to ensure operational performance targets are met
Agency resources needs:
- Traffic engineers to place signs and other field elements, establish proper messaging, monitor its effectiveness, and make modifications to the system
- Traffic management center staff to operate and monitor the HOT lane system
- Staff to administer the tolling program
Learn more about this strategy
FHWA, Office of Operations, High-Occupancy Toll Lanes website
The Washington Post, “Year-old 66 Express Lanes have caused shifts in commuter behavior, but not necessarily in ways officials hoped”, December 2018. https://www.washingtonpost.com/local/trafficandcommuting/year-old-66-express-lanes-have-caused-shifts-in-commuter-behavior-but-not-necessarily-in-ways-officials-hoped/2018/12/08/6e78d944-e832-11e8-a939-9469f1166f9d_story.html?utm_term=.c69df6d61885
San Francisco Chronicle, “Clean-air vehicles’ free tolls in express lanes are on the way out”, November 2018.
About key characteristics
HOT lanes are appropriate for heavily congested freeway corridors.
Costs are high and include toll lane equipment and back office tolling systems. However, recurring toll revenue has the potential to significantly offset the upfront capital costs.
HOT lanes have substantial technology requirements, including transponders for vehicles, roadside equipment to identify eligible vehicles, electronic signs, sensors to measure traffic volumes and speeds, monitoring cameras, and sophisticated central software to manage the application.
Collaboration for HOT lanes is high, requiring extensive coordination with the freeway management agency (if different from the HOT lane operator), transit providers, law enforcement, and public and community groups to provide education and work through equity issues and concerns.