Managed lane

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.

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 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.

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 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: