"Managed lanes" are defined as a limited number of lanes set aside within an expressway cross section or lanes comprising a separate expressway facility where multiple operational strategies are utilized and actively adjusted as needed for the purpose of achieving pre-defined performance objectives. The operation and utilization of managed lanes, typically situated within expressway rights-of-way, are controlled in order to optimize travel flow and reduce congestion. To move toward uncongested operations, managing a lane typically involves reducing excessive traffic volumes, reducing conflicts between vehicles, reducing the number of incidents, and better managing those incidents that occur.
Managed lanes can maintain the capacity of a highway facility under a wider variety of future scenarios than unmanaged facilities. While many people believe that good central planning can produce a network of uncongested highway facilities through enlightened engineering and construction, the truth is that a dynamic region will have growth and change that simply can't be foreseen. Congestion will occur on our highway system even when prior planning took into account all likely future conditions. We are limited in our response to changes by the financial constraints we have to live with, so we cannot respond immediately to changes with new construction projects. Thus, highway facilities need to be sufficiently resilient to function in a variety of future scenarios. The ability to manage the use and operations of a facility enhances this resiliency, and assures that the facility can operate closer to its optimum usage over the life of the facility.
Managed lanes require substantial investment over and above a basic facility. This investment includes the cost of an enhanced facility, technology, and personnel. A larger, better-funded cadre of transportation operations personnel would be required. In addition, new trained enforcement personnel would be required to implement rules governing managed lanes.
The following summarizes the most commonly applied managed lane strategies:
Dedicated Lanes. Express lanes and reversible lanes separate vehicles by trip destination and by vehicle type. Express lane facilities typically serve passenger cars only and provide point-to-point service with a much lower frequency of access and egress points. Conflicts and weaving are minimized in express lanes, optimizing capacity. Structural barriers are the primary means of assuring optimum system performance.
Congestion pricing allocates capacity through a traveler's willingness to pay. Prices are usually set so that speeds do not approach congested levels. Variable toll lanes and dynamic toll lanes are a form of congestion pricing applied to managed lane concepts.
Vehicle Preferences. Lanes can be managed by restricting or encouraging certain vehicle characteristics. For example, lanes can be restricted to trucks only, buses only, long-length vehicles (trucks and buses), passenger vehicles only, or high-occupancy vehicles (HOV's). HOV's are passenger vehicles with multiple occupants, including commuter vans and buses.
High-occupancy toll lanes (HOT lanes) further enhance congestion pricing and managed lane concepts by allowing high occupancy vehicles (HOV's) to utilize assigned lanes to maximize person throughput.
Supporting Technologies and Strategies. Managed lane strategies depend heavily on the successful application of several operations strategies and technologies. These strategies and technologies may include:
- Traffic Operations Centers
- Variable Message Signage (VMS)
- Overhead Lane Usage Signal Systems
- Closed Circuit TV (CCTV) Monitoring
- Electronic Toll Collection
- Variable Speed Limits / Speed Management
- Direct and Priority Access Ramps
- Lane Separation Systems: Fixed and Movable Barriers
- Enforcement – Police and Video Assisted
Each of these will be discussed in more detail below.
Should highway traffic be actively managed to reduce regional congestion?