Roles of Transportation Management Centers in Incident Management on Managed Lanes
Introduction and Background
Managed lanes are becoming an increasingly popular strategy to address traffic congestion, because they efficiently carry large numbers of people within a small amount of roadway space. This guidebook examines traffic incident management (TIM) practices that are implemented by transportation management centers (TMCs) and evaluates their use in the unique operating environment of managed lanes. This guidebook provides a framework for successful development and implementation of a TIM program using a TMC in the managed lane environment. It can be of use to planners developing new managed lane facilities, and transportation professionals who oversee existing managed lane facilities looking to optimize the use of their TMC and make their TIM program as effective as possible.
Managed lanes function as a "freeway within a freeway" and employ proactively implemented operating strategies in response to changing conditions. The goal is to have the managed lanes operate efficiently and reliably, with little or no congestion, to provide a higher level of service to eligible vehicles. Vehicle eligibility can be based on the type of vehicle (bus, truck, transit vehicle), the number of occupants in the vehicle, or the willingness to pay a toll. The most common types of managed lanes include High Occupancy Vehicle (HOV) lanes, Express Toll lanes (ETLs), and High Occupancy/Toll (HOT) lanes. The latter two categories utilize congestion pricing with variable toll rates that rise and fall based on traffic demand to "price out" low value trips and maintain the higher level of service in the managed lane.
Efficient TIM is critical for the success of a managed lane facility. Incidents that occur in managed lanes will affect greater numbers of people, as vehicle occupancy rates are typically higher in managed lanes than other lanes. The users affected by an incident in a managed lane are typically those road users with the highest priority within the transportation network, such as HOVs or transit vehicles. The reliability of the managed lane depends on quick clearance of incidents. Otherwise, operators cannot provide reliable service to users, which may limit the effectiveness of the facility.
Unique Aspects of TIM in Managed Lanes
The TMC will typically have unique capabilities and functionalities for the managed lane system since the managed lanes must respond to changing traffic conditions. Therefore the TMC's ability to detect an incident is enhanced, and the amount of operational control that a TMC has over a managed lane is also enhanced through the use of Intelligent Transportation Systems (ITS). Financial considerations are important during TIM in priced managed lanes, as there will be revenue loss if tolls are suspended or the facility is closed.
The method of separation between a managed lane and the parallel general purpose lanes can present challenges during TIM for responder access and diversions. Several facilities use permanent physical barriers which create an access limitation. Others use flexible posts or movable barriers that can be crossed during an incident. Many managed lanes rely solely on driver compliance with painted lines and buffer zones and have no physical separation.
TMC Role in the Managed Lane Environment-TMC Preparedness
The TMC role in TIM in managed lanes is generally similar to its role on other highway facilities; however the TMC must be aware of the additional challenges when an incident occurs within a managed lane environment. A TMC will typically have access to robust technology and communications capabilities. These capabilities can detect incidents, enhance necessary interagency coordination, and collect and disseminate data to stakeholders. Data sharing agreements and communications protocols have been established to facilitate this sharing of information along the managed lanes corridor. Interagency coordination protocols and agreements are in place between all TIM stakeholders. These agreements will involve other transportation agencies operating along the managed lane corridor in addition to response agencies, and should clearly define each agency's responsibilities. As part of the agreement, a designated point of contact at each agency for planning-related matters should be identified, and a communication protocol with multiple points of contact at each agency established for real-time operational matters. The goals of such agreements are effective coordination among all agencies, proper dissemination of information, TIM, and transportation system management during an incident.
A TMC or managed lane operator will typically have enforcement agreements with local law enforcement agencies. These enforcement agreements will be focused on enforcing compliance with access rules and enhancing operation of the managed lanes under normal circumstances. These law enforcement agencies may also be responsible for roadway service patrols, and will also typically be the first responders at the scene of an incident. Therefore, enforcement agreements should not only account for normal circumstances but should also account for the agency's role during an incident. Procedures for TIM in the operating environment of the TMC, and defining the appropriate level of enforcement should be part of the agreement. A TMC will have many other resources available to support TIM in the managed lanes. In priced managed lanes, toll revenue may be used to support the operation of the TMC and its activities. A portion of these funds and resources could be allocated to further the goals of the managed lane and provide a higher level of service to high priority vehicles in the transportation network.
A TMC should be involved in the early stages of planning for a managed lane facility, as this will ensure that TIM needs are taken into account during the design of a managed lane concept. The TMC will have knowledgeable staff that can provide valuable input into the design process, including the design and maintenance needs for ITS components, managed lane control software needs, the overall systems engineering process, and the physical designs of the managed lane, such as the location of access points and the type of separation treatments used. The TMC can also provide valuable input into the operational planning for the managed lane, including integration of the managed lanes with established ITS strategic plans and ITS regional architectures.
The TMC plays a key role in development of operation plans, maintenance plans, and the TIM programs and performance measures that will be used on a managed lane facility.
TMC Role in the Managed Lane Environment-Real Time TIM Response Activities and Support
While multiple transportation agencies may be responsible for operation of the corridor on which the managed lane operates, the TMC must treat the network as a single transportation system when coordinating during an incident. Interagency agreements and joint communications protocols ensure that the various agencies work efficiently to clear the incident and carefully monitor the effects. This includes the effect of any incidents in the general purpose lanes that may affect the operation of the managed lanes or require use of the managed lanes for the response. The ability of the TMC to coordinate among multiple agencies is key during incident detection and verification, as the TMC may detect an incident outside of its primary jurisdiction or may receive reports of an incident from another TMC, especially if multiple TMCs operate along one corridor.
The response to an incident in a managed lane may be complicated by the physical access to the lanes. It may be worthwhile to have dedicated response vehicles, such as tow-trucks, pre-positioned at key locations along the managed lanes if recovery vehicles may not be able to easily access the lanes. Safety patrol vehicles on a patrol route provide a valuable source of incident detection and verification information. These vehicles can be dispatched by a TMC to the scene of an incident to assist with establishing a TIM zone, and can provide the TMC with accurate real time information which can be relayed to other agency partners. Quick and efficient response is important for minimizing facility downtime, maintaining access for priority vehicles, and reducing revenue losses on priced managed lanes.
A TMC may have the ability to support TIM by temporarily reducing demand on the managed lanes through the use of vehicle access management strategies. This could involve a vehicle eligibility change, which can be implemented by raising the vehicle occupancy threshold or eliminating access to the managed lane by vehicles paying a toll, in effect temporarily operating a HOT facility as an HOV facility. Priced managed lanes that have flexibility in setting prices can adjust toll rates to discourage vehicles from entering the lanes. In other cases, access to the managed lanes can be closed by activating Dynamic Message Sign (DMS) units, gates, or lane control signals. On managed lanes without access control features, the TMC can direct responders on the ground to block access to the lanes.
The TMC will also support TIM in the managed lane by providing scene management support to responders, which is especially important when the managed lane has limited room to establish a typical TIM zone. ITS devices are used to notify travelers of the incident and actively monitor the scene. Coordination with partner agencies, maintenance of close communications with those agencies, and dispatching of additional resources needed to support an effective incident scene will take place in the TMC. Another function of the TMC is to provide traffic control support, which will supplement any vehicle access management strategies implemented. This includes typical traffic control functions of a TMC, coordination between agencies in the managed lane environment, monitoring and tweaking of the plan as needed, and coordinating the opening of movable barriers where required for the response. If diversions are needed, such as opening the managed lane to all traffic, the TMC will coordinate the implementation of the management strategy.
The final stage of the TIM process is the clearance and recovery phase. The TMC will provide significant support during the recovery and clearance process with the goal of restoring normal operation as quickly as possible to reduce the impacts to managed lane users. The support provided will include coordination of necessary clearance and infrastructure repair resources. With the TMC's coordination and resource planning abilities, the incident can be cleared as quickly as possible.
The TMC may have the ability to provide system and corridor management, as an incident may affect other parts of the transportation network well beyond the scene. TMCs may have the ability to implement some or all of these strategies. They include use of lane control signals, ramp metering, adjusting traffic signal timing, posting travel times, implementation of diversions including modal transfers, providing traveler information, and expanding motorist assistance patrols. These actions can be implemented through the coordination of multiple TMCs and agencies to have a true corridor effect of the TIM strategies implemented.
Eight managed lane facilities in the United States were used as case studies for this guidebook:
The case study review revealed significant variation in the operation and physical design of these managed lane facilities, as well as the TMC role in TIM. A table containing a detailed comparison between the eight facilities can be found in Chapter 5 of this guidebook. Key findings are summarized as follows:
Additional findings about the case studies are discussed in detail in Chapter 5. Furthermore, three of the eight managed lane facilities investigated for this guidebook are presented in greater depth as case studies in Chapter 5 of this guidebook; Minneapolis's I-35W Priced Dynamic Shoulder Lane (PDSL), Houston's Katy Freeway Managed Lanes, and Northern Virginia's I-495 Express Lanes.
In order for managed lanes to function properly, the facility must operate reliably with minimal downtime. The TMC supports this by properly preparing for TIM activities that will occur on the managed lanes, and then by supporting the real-time TIM activities during an incident.
United States Department of Transportation - Federal Highway Administration