A managed lane is a type of highway lane that is operated with a management scheme, such as lane use restrictions or variable tolling, to optimize traffic flow, vehicle throughput, or both. Definitions and goals vary among transport agencies, but managed lanes are generally implemented to achieve an improved operational condition on a highway, such as improving traffic speed and throughput, reducing air pollution, and improving safety. Types of managed lanes include high-occupancy vehicle (HOV) lanes, high-occupancy toll lanes, express toll lanes, reversible lanes, and bus lanes. Most managed lane facilities are located in the United States and Canada, although HOV and bus lanes can be found in many other countries; outside of the US and Canada, many countries use active traffic management that manage all lanes of a highway.
Definition The definition of a managed lane varies among transport agencies. The United States' Federal Highway Administration describes managed lanes as "highway facilities or a set of lanes where operational strategies are proactively implemented and managed in response to changing conditions". The FHWA notes that among US transport agencies, definitions of managed lanes contain three basic elements: "The managed lane concept is typically a 'freeway-within-a-freeway' where a set of lanes within the freeway cross section is separated from the general-purpose lanes." "The facility incorporates a high degree of operational flexibility so that over time operations can be actively managed to respond to growth and changing needs." "The operation of and demand on the facility is managed using a combination of tools and techniques in order to continuously achieve an optimal condition, such as free-flow speeds." The Texas Department of Transportation defines a managed lane as "one that increases freeway efficiency by packaging various operational and design actions. Lane management operations may be adjusted at any time to better match regional goals." Typical goals and objectives for managed lanes are improved traffic efficiency, increased traffic throughput, improved safety, and reduction of pollution to meet regional air quality goals.
If designed to improve travel conditions on a highway, the following types of lanes can be considered managed lanes: High-occupancy vehicle (HOV) lanes, tolled lanes built within or along an existing highway (express toll lanes), high-occupancy toll (HOT) lanes, reversible lanes (British: tidal flow), truck lanes, interchange bypass lanes (usually for HOV, truck, or mass transit only), bus lanes, use of shoulders by traffic in certain circumstances (dynamic shoulder lanes), and dual/parallel highways of which one is managed.
Managed lanes are essentially a limited application of active traffic management to only some of a highway's lanes, rather than all lanes of the highway.
Reasons for managed lanes The most important prerequisite condition necessary for managed lane demand to materialize is the presence of recurring traffic congestion. Managed lanes are by definition a congestion management strategy and have benefits that are only fully realized in the context of frequent traffic congestion that causes significant travel time delays and uncertainty over trip time reliability. Although there is no broadly accepted definition of what constitutes traffic congestion, congestion is generally identified as a breakdown in the flow of traffic and a reduction in vehicle speeds caused by traffic demand approaching or exceeding available roadway capacity. These situations generally correspond to a level of service of D or worse (on a scale A-F, with A being highest) and average travel speeds of 30 mph or less, although this does not mean that other scenarios are not suitable for managed lane strategies.
The specific characteristics of the traffic demand that exists in a corridor are particularly important when considering managed lane strategies. Traffic demand on urban roadways is typically variable and changes depending on the time of day, day of the week, and by season. It is common for demand in some radial corridors to be highly directional, with demand for facilities leading into a central business district often being highest in the morning peak periods and demand for outbound directions being highest in the afternoon periods. These patterns cause an imbalance of demand that require solutions that are flexible in their ability to accommodate variable and directional traffic volumes. Routes that connect suburban trips may exhibit bi-directional demand and be congested for more prolonged periods, so the selected concept needs to recognize this. Demand may exist for one particular mode, say transit for a radial corridor, and not for another. Each type of demand should be separately analyzed, even if they will share the managed lane facility.
Strategies for implementation
Strategies for managing lanes typically fall into one of three categories. These include pricing, vehicle eligibility, and access control. Most managed lane implementation incorporate the application of multiple management strategies. In the United States, managed lanes are almost always located within the right-of-way of freeways, often on the left or "high speed" side of the mainlanes, but sometimes on the right lane or shoulder lane for short distances. Agencies often combine lane management strategies and applications of various intelligent transportation systems (ITS) and traffic control devices to address both safety and operation needs. Examples include: Employing static signing to notify drivers of eligibility to use a dedicated lane and times indicating when restrictions are in place. Utilizing overhead lane control signals and/or changeable message signs to accommodate highly directional demand on reversible or contraflow lanes. Employing access treatment and lane separation strategies to manage the speed differential often associated with managed lanes. Increasing the level of automated and on-site monitoring, enforcement and incident response capability to help assure travel time reliability and safe operations. Implementing variable pricing through electronic tags that vary tolls by time of day or by demand to more efficiently utilize lane capacity.
Although managed lanes have traditionally been added as new capacity, the concept does not explicitly require capacity expansion. Instead, the focus of managed lanes is to preserve a reliable trip that is viewed as a preferable alternative over congestion that exists in the general purpose lanes. Therefore, the correct objective for managed lanes is not necessarily congestion relief, but rather, improved management of congestion that provides relief to users and non-users.
The rationale of implementation does not suggest that incorporation of managed lanes should be a stand-alone strategy. Indeed, the best applications are ones in which managed lanes are an integral component of a comprehensive congestion management program incorporating an array of other treatments and strategies. These treatments may include ramp metering, incident management, traffic demand management (TDM) such as vehicle for hire promotion, and associated programs that are both complementary and synergistic to overall regional mobility goals. For example, restricted lanes for buses and carpools only make sense and draw sufficient patronage when parallel programs including transit services, park-and-ride / park-and-pool lots and trip matching are implemented. Ramp and connector metering offers the opportunity to provide bypass lanes for transit and other transportation modes to attract demand.
The rationale for application is predicated on an understanding of the specific operational problem evidenced and forecasted to exist. The design should not define the operational need, but rather respond to the intended operation and attempt to fit within the specific corridor constraints that are often present. For example, highly directional congestion (i.e., inbound in the morning and outbound in the evening) may be addressed by a variety of different treatments such as concurrent, reversible or contraflow operations, and each will require a different design that may or may not fit within the corridor. The presence of congestion in both directions during the same daily commute may suggest only a bi-directional, concurrent flow operation (e.g., one dedicated lane operating in each direction) is appropriate. Similarly, the specific operational attributes of how many hours the managed lane is active, where access is applied and who can use it are determined in successive levels of evaluating the observed and forecast operational problems.
Types of managed lanes
Pricing(1)
Toll managed lanes
Toll managed lanes use tolling, with electronic toll collection, (ETC), to manage the traffic flow of the managed lane.
Toll managed lanes should be contrasted with a regular toll road, as regular toll roads have the toll apply for every single lane, not just a few. Furthermore, express toll lanes should be contrasted with express lanes (as express lanes do not charge any toll).
The most general form of toll managed lanes are express toll lanes (ETL), which have variable tolls to maintain a higher throughput or speed in the ETL lane compared with the other lanes of the highway. ETLs are essentially access restricted tollroads within the freeway right-of-way that are actively managed to preserve free-flow operating conditions. The tolls are frequently changed to maintain a steady flow of traffic; in some cases, the goal of toll fluctuations is to maintain a minimum speed on the ETLs (e.g. 55 mph/85 km/h). As the lanes approach their capacity, tolls are increased to discourage vehicles from entering the ETLs.
A common variant of Express Toll Lanes (ETLs) are high-occupancy toll (HOT) lanes. HOT lanes are free for high-occupancy vehicles, while vehicles with fewer passengers pay a toll. Some types of vehicles may be exempt from tolls, such as hybrid vehicles (including single-occupant hybrid vehicles in HOT lanes), registered carpools (on ETLs), and motorcycles. Some toll managed lanes may only be tolled at certain times or charge different rates for high-occupancy vehicles.
Toll managed lanes are sometimes included in a highway reconstruction project to not only improve traffic, but also to fund the construction project itself (including improvements to existing lanes) through public-private partnerships (P3). In such highway reconstruction projects, the government transport agency tenders a P3 project in which a private consortium of companies designs, finances, and rebuilds a section of highway after which they are given a concession (e.g. 40 years) to operate the toll managed lanes, receiving fixed payouts from the relevant government transport agency for meeting performance criteria. These payments are used to repay the loans made by the private consortium, which keeps any excess as profit.
Vehicle Eligibility (2) One of the most commonly used lane management tools for the past 40 years is restricting use based on vehicle eligibility. Eligibility can be defined in terms of vehicle type (i.e. buses, trucks, motorcycles, or hybrids) or by the number of occupants in a passenger vehicle, such as two or more (HOV 2+) or three or more (HOV 3+) in a vehicle. The latter definition represents the vast majority of managed lanes found in the US and Canada: HOV lanes.
HOV lanes