Currently limited land availability, scarce funds, and social and environmental concerns prevent many agencies from adding new freeway lanes. The combination of these factors is forcing transportation planners and engineers to explore new ways to more effectively operate the existing transportation network. Thanks in part to the enabling capabilities of ITS technologies, the use of managed lanes is one such concept that is being used successfully across the country. The managed lane operational approach can offer peak period free-flow travel to certain user groups, which might be high occupancy vehicles (HOV), trucks, toll-paying vehicles, transit, low-emitting vehicles, or some combination of these and other groups. However, little is known about the complexities of designing a practical, flexible, safe, and efficient facility that may have multiple operating strategies throughout the course of a day, week, year, or beyond.
Based on the research done by TTI, lessons learned have been developed on effectively deploying ITS to provide user information in managed lanes facilities.
Managed lanes are used to offer additional choices to motorists on a section of freeway. These choices can vary by time of day or possibly in response to changing traffic conditions on either the managed lane or the other general-purpose lanes in the corridor. The extent to which travelers can and will accommodate such operational flexibility hinges on getting the right information, at the right time, and in the right format so that they can make effective decisions pertaining to their trip. Managed lanes facilities may present drivers with unfamiliar access, geometries, and operating rules. Conveying information concerning these features requires effective use of standard traffic control devices in novel ways, such as modifying the design and placement of both fixed and dynamic message signs (DMS). The information needed to support such decisions must be safely and effectively interwoven with that information required for motorists to safely control, guide, and navigate their vehicles into and along the managed lanes. To further complicate matters, this information must also be interwoven with similar control, guidance, and navigation information required for motorists operating in adjacent general-purpose lanes.
- Implement dynamic message signs in conjunction with fixed signage to display managed lane information. Dynamic message signs (DMSs) can be an important instrument used to display information regarding managed lane facilities. Large, overhead DMSs are commonly used along managed lanes. These signs allow for traffic conditions, incident notification, travel times, and tolls to be displayed dynamically. With newer electronic technology, the diamond symbol can be displayed in full height on the sign to mimic the design of an overhead regulatory sign. Existing guidelines concerning message construction and message phasing should be followed for managed lane applications. Agencies may wish to consider placing a static plaque identifying the applicable lane above DMSs if the information in the sign applies only to the managed lanes.
- Present signs so information for managed lanes is clearly separated from information for general-purpose lanes. Sign placement is a difficult issue for managed lanes facilities. The Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD) provides somewhat confusing information as to when signs should be placed overhead, on the right shoulder, or on the left-side median barrier. Particularly for concurrent-flow facilities with limited access areas, conflicting information regarding distances to exit points for the managed lanes and general purpose lanes may exist. In these situations, it is critical that signing displays be designed so as to clearly separate the information for the managed lanes from that intended for the general-purpose lanes. In general, overhead signs are often preferable on freeways because they are visible to all lanes and will not be blocked by large vehicles. Overhead signs, however, can be extremely expensive to install and often require lane closures for maintenance activities. A common practice is to erect a large sign structure that spans the full width of the roadway. Guide signs for general purpose and managed lanes are then all placed on the same structure. Separate cantilevers rather than full-span sign structures are preferred to separate this information. If separate cantilevers are not possible, managed lanes signs should be as far left as possible, preferably with a noticeable gap between them and signs for the general purpose lanes.
- Provide enough pertinent information for drivers to make informed decisions. Managed lane facilities are more likely to present unfamiliar decision-making needs for drivers that have not experienced them before. Additionally, with the newer combinations of managed lane types, users that may be familiar with more traditional managed lanes (i.e., HOV-only lanes) may still be confused by such combinations as HOV/HOT lanes or toll lanes with dynamic pricing. They may not have knowledge of the hours of operation, enforcement regulations, or how and when to pay, or if payment is even necessary. In order to make a properly informed decision a driver must be able to take in several different types of information relating to: the managed lane, traffic conditions, and their vehicle. The specific content for each information type that may need to be presented to drivers includes:
Managed lane information:
- Type of managed lane (HOV, fixed toll, variable toll, transit-only, some combination of these)
- Vehicle restrictions
- Hours of service
- Open/closed information
- Entrance information
- Exit information for the managed lane
- Tolling information (if any)
- Required method of payment (if any)
- Penalty for improper use
Traffic condition information:
- Current traffic congestion in general-purpose lanes
- Incident management information
- Travel time and estimated time savings for use of managed lane
- Occupancy requirements
- Presence of transponder or cash (if required)
- Specific prohibitions of certain vehicles (trucks, towed trailers)
- Minimize driver information overload by using innovative managed lane information dissemination methods. Not all drivers are able to process information at the same capacity, and it is possible to provide so much information that some drivers are overloaded. Additionally, as many types of managed lane information are complicated and come with general-purpose lane information, drivers can be hard-pressed to correctly read and process all the information provided. Presenting information in such a way as to minimize driver information overload will allow more drivers to understand managed lane information and increase the likelihood of future use. Previous research recommends that roadside information not exceed four panels per sign of information, with less than six units of information on each panel. See http://tti.tamu.edu/documents/0-4160-13.pdf for more information on the information elements and characteristics. A review may reveal that some of the information can safely be shifted upstream or downstream to spread the information load. Based on current trends and results of focus groups, several innovative methods of managed lane information dissemination are recommended. These include:
- Color-code signs for better differentiation between information intended for managed lane traffic and that intended for general-purpose lane traffic. This coding could take the form of banners across the top of the sign, or the color of the entire sign. Further research is needed to determine the manner that would aid drivers the most in understanding the information presented, and the amount of benefit that can be achieved through this type of coding process.
- Remove managed lane information from signs that can be effectively presented in other formats to drivers. Examples of other dissemination methods include highway advisory radio, Internet, and direct mailing to electronic transponder carriers.
- Consider the intended target user group for the managed lane early in the design process. This allows better assessment of decisions on how much and what type of managed lane-specific information should be included. This early consideration can also allow for innovative information dissemination strategies, such as direct mailings to transponder subscribers. Furthermore, engineers will be better able to design the facility with the information needs fully addressed rather than as an afterthought at the end of the project.
Presenting drivers with sufficient, easily disseminated and understood, information is a key factor to achieving more efficient use of managed lane facilities. In order to avoid information overload it is critical that signs, regarding managed lane usage, are to the point and clearly separate from general purpose lane information. Information relayed in an organized and understandable fashion is more likely to be absorbed by drivers, leading to increased use of managed lanes and higher levels of customer satisfaction. To convey information agencies need to use DMS in conjunction with fixed signs, especially in corridors where there are variable tolls. The increased levels of information will assist drivers in their decision making process and improve overall customer satisfaction. Ensuring drivers are fully aware of managed lanes facilities and their requirements, is essential if they are to be utilized by drivers of all levels.