Designing for Transportation Management and Operations: A Primer
3. Design Considerations for Specific Types of Operations Strategies
Proper design of operational elements and inclusion of M&O considerations in typical infrastructure projects provide an opportunity to maximize the efficiency of a transportation system. Future deployments can be jeopardized when operations considerations and provisions are not included in projects. This chapter provides an overview of M&O strategies and considerations for incorporating operations into the design of transportation projects. It is intended to help designers understand what design issues may be associated with specific operations strategies and how to include these strategies on typical transportation infrastructure projects. It should be noted that many of these strategies can also be deployed on a standalone basis where appropriate. Many strategies and design considerations described in this chapter are repeated in various sections due to the overlap and interdependence of these strategies. For example, freeway management and arterial management are essentially broader categories that include elements of subsequent sections of the chapter, such as managed lanes, active traffic management, and maintenance. The decision of which operations strategies to consider during the design of projects may often be driven by overarching operations objectives and a concept or plan for managing and operating the transportation system.
3.1 Freeway Management
Freeway operations and traffic management involve managing travel and controlling traffic. The application of appropriate policies, strategies, and actions can mitigate any potential impacts resulting from the intensity, timing, and location of travel and can enhance mobility on highway and freeway facilities. Freeway management systems can improve the efficiency of available capacity, improve safety, and support TIM activities. These systems can also be used to mitigate existing features in the cases of curve warning systems or runaway truck ramps.
The FHWA's Freeway Management and Operations Handbook states: "Freeway traffic management and operations is the implementation of policies, strategies and technologies to improve freeway performance. The over-riding objectives of freeway management programs are to minimize congestion (and its side effects), improve safety, enhance overall mobility, and provide support to other agencies during emergencies." By following the strategies and design considerations described in this chapter, designers can support the strategies described in the Handbook.34
During the design phase for freeways, many operational strategies need to be accommodated. Design for non-recurring congestion caused by weather events, accidents, construction, emergency repairs, and other events must be integral to the physical design of the facility.
As technology has become more integrated with the transportation system, the opportunity to utilize ITS and other means to manage freeways has become more prevalent. Various devices and systems placed on freeways, including CCTV, dynamic message signs (DMS), and ramp meters, have changed the way freeways are operated, but have not adequately changed the way they are designed. ITS and other technologies are too often treated as an afterthought in the design process; designers tend to "fit them in" rather than design optimal locations for them.
The challenge now is not just to include technology in a project, but make it a seamlessly integrated portion of the design, similar to the design of stormwater management, utilities, or guardrail. When ITS is included on a new or reconstructed facility, efforts should be made to integrate the devices and communications into the overall design of the facility in order to ensure optimal placement of the devices. Since ITS is used to monitor and manage the freeway, the locations of devices are crucial. For example, a DMS displaying a message to travelers about the congestion they are currently sitting in is not located in a place where it can have maximum effectiveness. Rather than locating the sign where there is available right-of-way, the sign should be located to improve the operation of the facility. Considerations such as sun glare, guide sign spacing, spacing from the next interchange, and visibility due to horizontal or vertical curvature are just a few of the design considerations for placement of a DMS, as well as for other freeway management strategies. To embrace designing for operations, designers must explore these considerations within the framework of the overall design of the facility.
Table 1 identifies elements to consider during design that can impact freeway operations. It also shows potential opportunities for designers to structure their roadway design (or redesign) to allow for more cost-effective implementation of freeway management strategies in the future. Some of these design considerations would apply to multiple strategies.
An additional resource to supplement the design considerations for ramp meters listed in the table below is the FHWA Ramp Management and Control Handbook.35 This reference contains a section focused on design considerations for ramp metering based on a variety of ramp metering design manuals and guides from across the United States.
3.2 Arterial Management
Arterial management involves implementing practices and operations strategies that promote the safe and efficient use of arterial roadway capacity to manage congestion. It also promotes the idea of treating the transportation system as a network that serves transit, bicycles, and pedestrians in addition to motorists. Improved modeling capabilities have improved understanding of how the transportation system is a connected network: what happens in one location affects another. Design of freeway, arterial, and bridge projects must consider impacts on the operations of the local transportation network. Agencies must work together regardless of jurisdiction to ensure the proper strategies are put in place to mitigate the impacts on the surrounding network.
Successfully managing the safety and performance of arterials involves the following core functions:
3.2.1 Cooperation of Municipalities
Because arterials often fall under the jurisdiction of different agencies, managing arterials properly requires cooperation and collaboration with neighboring communities. A project under one jurisdiction should achieve a level of operation similar to the rest of the corridor. In order to accomplish this, agencies may need to form agreements. For example, to move traffic through the signals on a multi-jurisdictional corridor in order to maintain traffic flow, a designer may need to connect to another agency's network to share intersection data, share information on preemption for transit and emergency vehicles, or consider special event timing plans.
These agreements can be formal concepts of operations or memoranda of understanding, or they can be informal "hand-shake" agreements that have been institutionalized through years of effort. Designers must educate themselves on the content of these documents or other collaborative arrangements to understand how a project may impact the arterial as a whole. These agreements help agencies share a common language regarding operational goals, performance measures, and strategies to manage the arterial.
3.2.2 Managing Access for All Modes
Managing access is a primary strategy for improving operations on an arterial. Many agencies have guidelines on design elements such as driveway spacing, corner clearance from major intersections or interchanges, and the optimum location of signals and roundabouts. While these provide foundational knowledge to apply to arterials, designers cannot expect to follow the guidelines exactly, as adjustments are often necessary.
Designers should check for operational impacts due to deviations from these guidelines. For example, when implementing context-sensitive solutions such as road diets and adding bicycle facilities, the operational impacts of the following should be considered:
3.2.3 Monitoring and Actively Managing Traffic Conditions and Intersection Signalization
Designers planning physical changes to an arterial roadway will need expertise in traffic operations in order to evaluate these changes because a simple report about level of service will not adequately address operational issues. Proper design and management of intersection traffic signalization is essential to optimizing the operation of arterial roadways. Designers must consider the overall corridor and roadway network signalization concept when designing a project for individual intersections. Questions about managing queues, operating speeds, safety modeling, and impacts due to growth in traffic and increases in pedestrian and bicycle modes need to be addressed. Designers should provide for in-pavement loops or other traffic monitoring devices to allow for operational assessments, including signal timing and progression.
Table 3 identifies elements to consider during design that can impact arterial operations. It also shows potential opportunities for designers to structure their roadway design (or redesign) to allow for more cost-effective implementation of arterial management strategies in the future. Some of these design considerations would apply to multiple strategies.
3.3 Active Traffic Management
Active traffic management (ATM) and managed lanes (see Section 3.4) are becoming increasingly popular in the United States as facility operators seek innovative solutions that can improve throughput and safety on congested facilities largely within the footprint of existing highways, thus requiring little or no roadway widening.
ATM is the dynamic management of recurrent and non-recurrent congestion based on current and forecasted traffic conditions. ATM focuses on maximizing trip reliability through approaches that seek to increase throughput and safety through the use of integrated systems and new technology. ATM includes the automatic and dynamic deployment of M&O strategies to optimize performance quickly and avoid the delay that occurs with manual deployment.
Some ATM strategies, such as ramp metering and variable speed limits, have been successfully implemented within many parts of the United States. Most other ATM strategies are relatively new concepts in the United States; however, they have been successfully implemented in many parts of Europe.
3.4 Managed Lanes
Managed lanes are highway facilities or a set of lanes where operational strategies are proactively implemented and managed in response to changing conditions. Managed lane projects take lane management strategies that have been used extensively for decades-such as HOV lanes, bus-only lanes, truck lane restrictions, and express lanes-and incorporate the concept of active management. These strategies can be implemented utilizing concurrent flow lanes (adjacent to general purpose lanes), reversible flow lanes, contra flow lanes, or existing shoulders. Colorado DOT took enforcement needs into consideration when designing their high-occupancy toll (HOT) lanes by adding a widened shoulder (see Figure 21).
Caltrans issued guidance in 2011 titled "Traffic Operations Policy Directive 11-02 – Managed Lane Design," which institutionalizes the practice of designing for operations. The directive states that it "shall be applied during the planning and development of freeway managed lane projects, including conversion of existing managed lanes to incorporate tolling or utilize continuous access. It shall be considered during the planning and development of all other freeway improvement projects (e.g., pavement rehabilitation project) and during the course of traffic investigations that are addressing operational and safety performance deficiencies."36
Table 5 identifies elements to consider during design that can impact managed lane operations. It also shows potential opportunities for designers to structure their roadway design (or redesign) to allow for more cost-effective implementation of managed lane strategies in the future. Some of these design considerations would apply to multiple strategies.
During the design of a transportation facility, the transit rider must be considered just like the motorist. Transit provides the ability to increase the throughput of a facility, thereby improving overall facility operations. There are opportunities on both freeway and arterial facilities to incorporate transit operations considerations into design. One high profile application for transit on freeways is bus-on-shoulder (BOS) or bus-only shoulder. There are documented examples of BOS in California, Florida, Georgia, Maryland, Minnesota, New Jersey, Virginia, Washington, and Delaware. Minnesota is a leader in BOS operations, with more BOS lane miles than the rest of the country combined.
Minnesota DOT has developed guidelines for geometric design and signing for bus-only shoulder operations.38 Geometric standards regarding lane widths, vertical clearance, stopping sight distance, and lateral clearance/clear zone must be considered and may not always be full design standards for retrofit applications.39 Figure 22 shows the use of minimum 10-foot shoulders.
An FHWA report titled Efficient Use of Highway Capacity describes recommended spacing and design of emergency refuge areas for stalled vehicles when implementing BOS.40
A BOS program ensures that buses can achieve significant travel time savings by not having to enter the weave through general purpose traffic to enter or exit an interior managed lane. Some of the routes in Minneapolis experienced a 9 percent increase in ridership. A successful BOS implementation requires highway designers and transit operators to work together to implement a solution that considers ramp operations, merging, and weaving. BOS can be implemented in conjunction with managed lane strategies or ramp metering.
Another important transit operations strategy is bus rapid transit (BRT). BRT is an advanced bus system that relies on several techniques to provide faster travel times, greater reliability, and increased customer convenience over ordinary bus service. BRT offers the flexibility of buses and the efficiency of rail by operating on bus lanes or other transitways and applying advanced technologies or infrastructure such as transit signal priority and automatic vehicle location systems.41
Florida DOT District 4 (Ft. Lauderdale) is studying transit queue jumps for use on heavily congested arterials, including the impacts of queue jumps on intersection and approaching roadway geometry. They will evaluate the traffic control devices and transit operator protocols associated with queue jumper operations and will assess their impact on other arterial traffic. They will develop a design "template" that can be utilized to identify intersections at which queue jumping should be provided and to guide the design/placement of associated traffic control devices and the design of any needed roadway modifications. The template will be systematically used in future resurfacing and other projects.
Transit operators understand best which strategies work best for certain corridors. Transit agencies should be engaged in design to help select the most appropriate features that allow for the maximum efficiency of the facility. Rather than retrofitting an existing freeway or arterial with these types of strategies on a case-by-case basis, they should be considered as part of an overall corridor management strategy and mainstreamed into the design process.
Table 6 identifies elements to consider during design that can impact transit operations. It also shows potential opportunities for designers to structure their roadway design (or redesign) to allow for more cost-effective implementation of transit strategies in the future. Some of these design considerations apply to multiple strategies.
3.6 Work Zone Management
Managing traffic during construction is necessary to minimize traffic delays, maintain or improve motorist and worker safety, complete roadwork in a timely manner, and maintain access for businesses and residents. Work zone traffic management strategies should be identified based on project constraints, construction phasing/staging plan, type of work zone, and anticipated work zone impacts.42
Agencies should consider performance-based maintenance of traffic requirements, such as maximum allowable delay, rather than geometric or time of day restrictions. This approach allows greater creativity and innovation by contractors, which may result in both cost savings to the agency and time savings to motorists.
A transportation management plan (TMP) is a successful approach to identifying transportation management strategies and describing how they will be used to manage the work zone impacts of a project. The FHWA publication Developing and Implementing Transportation Management Plans for Work Zones defines planning and design considerations for work zone management. Throughout the development of a TMP, designers and operational stakeholders have the opportunity to consider the impacts of their work zones and to identify strategies to improve work zone performance.43 The TMP is primarily intended for managing traffic during a construction project. However, some of the elements of the TMP, particularly ITS improvements, could remain in place to aid ongoing operations. Additionally, the cross-functional and interagency relationships formed during the development and use of the TMP should be continued after the project to promote a coordinated approach to operating the facility.
The inclusion of work zone management and operations should be identified during needs development and preliminary engineering so that strategies can be implemented prior to the start of major construction activities if needed. In addition, the transportation facility should be designed with construction and post-construction maintenance of traffic activities in mind. Designers must consider how the facility will be constructed in a manner that provides a safe working environment and minimizes the impact on the operation of the facility. This may require consideration of construction methods and staging.
Traffic capacity and shoulder/pullout areas are often restricted in work zones. Prompt detection and clearance of traffic incidents in work zones can help reduce secondary crashes and delay. Preparing a work zone TIM plan and using strategies that improve detection, verification, response, and clearance of crashes, mechanical failures, and other incidents in work zones and on detour routes can benefit safety and mobility. Specific strategies are identified in FHWA's, Traffic Incident Management in Construction and Maintenance Work Zones.44
3.7 Traffic Incident Management
Traffic incident management (TIM) practitioners become well aware of shortfalls in operational provisions when it affects their ability to respond to incidents safely and efficiently. There are several ways that designers can ensure that the needs of this end-user group are considered and included in the final design of a project. The National Unified Goal (NUG) for TIM is a foundational element of a well-developed TIM Program and provides a valuable opportunity to link program decisions to physical design. Table 7 identifies elements to consider during design that can address various NUG strategies.45
During the design phase, the project team should seek input on roadside safety from emergency responders or a TIM team at important milestones, such as the transition from preliminary engineering to final design. Input from responders on roadside features such as noise walls, median barriers, and ITS device locations should be considered a priority in the design process. If a local TIM team does not exist where the project will be located, the project team should establish one with the goal of creating a framework that will ensure continued TIM team existence after the project is complete. During construction, the TIM team should be engaged to ensure that both constructability and emergency response risks are balanced.
It is important to develop a good rapport with emergency responders during a construction project. An effective way to make the best use of their time and to gain valuable insights into their operational needs is to conduct a table-top exercise that includes the proposed design. After the design plans have reached a level that makes it clear what will change from the existing situation, the design team should gather the local TIM team members or establish the TIM team and conduct a table-top exercise to "test" the design for operations. In addition to agency design personnel, the team should include maintenance staff and emergency responders. It is suggested that at least three scenarios be included during this session to generate discussion:
In addition to documenting the needs of emergency responders in each of these scenarios, there should also be discussion about how the response to these scenarios differs if construction workers are present at the incident site. The response to less severe events should also be covered.
Transportation agencies need to deploy appropriate risk reduction methods to minimize or eliminate identified vulnerabilities in their system, and designers need to consider if countermeasures are appropriate for their particular project. NCHRP Report 525 – Surface Transportation Security discusses many of the tools and countermeasures that should be considered in the design phase as a means to improve the security of critical infrastructure and facilities, information systems, and other areas.47 Physical security countermeasures that should be considered by a designer may include signs; emergency telephones, duress alarms, and assistance stations; key controls and locks; protective barriers; protective lighting; alarm and intrusion detection systems; electronic access control systems; and surveillance systems and monitoring.
Agencies must conduct threat and hazard analyses for use in prioritizing the most important roads and infrastructure. Controlling access to critical components, providing standoff from critical components, eliminating single point of failure construction, and ensuring that surveillance systems are tied directly into response units are the best strategies to deter or prevent terrorist or criminal acts. Many of these strategies are very costly and must be considered in the scoping phase. Even though making these decisions is beyond the authority of the individual designer, there are related elements that can be considered in the design phase.
Designers should contact internal and stakeholder security and emergency management officials to develop security and emergency management requirements. This coordination can prevent issues such as designing and building a structure for standard loads then retrospectively learning that it is a critical primary route that must be designed for moving heavy equipment into an area during an emergency. Security and emergency management planning and designing takes a community of people drawn from law enforcement/security, fire and emergency medical services, emergency management, occupational safety, and highway/transportation organizations.
Table 8 identifies elements to consider during design that can impact infrastructure security. Transportation agencies must examine the threats against infrastructure and identify the most useful means to reduce the vulnerabilities associated with those threats to acceptable levels. Often less costly but more effective solutions are available that the agency can select to meet security requirements. In making these choices, designers can benefit from an analysis that compares one countermeasure against another based on protection provided, cost, and effort required.
3.9 Freight Operations
Freight operations are an important consideration with respect to improving mobility and productivity. Improved operation can benefit the freight industry through:
Additionally, improving freight operations enhances the safety and efficiency of the transportation system for all users by lessening the impact of freight movements on the general public and vice versa. Virginia DOT has been focused on improvements geared toward truck traffic along Interstate 81 (its most heavily traveled truck route) for years. Improvements include interchange redesign, truck climbing lanes, ITS improvements, and ramp extensions. During design, however, consideration of freight must extend beyond the geometric considerations associated with commercial vehicles to include operational elements that support enforcement and hours-of-service requirements, as well as elements to improve safety and overall efficiency.
The table below illustrates specific actions that designers can take to enhance freight operations. In some cases, where significant infrastructure improvements are involved, strategies must be initially considered in the scoping/planning phase. However, designers can optimize the effectiveness of these strategies through use of the specific design considerations.
Maintenance of a roadway can have a major effect on operations. Maintenance personnel have a variety of issues to deal with; from mowing operations in the summer, to snow plowing operations in the winter, to maintenance of roadside devices, they are constantly working to keep roadway networks operating. Taking into consideration certain aspects of the design of the roadway and devices can reduce the impacts of maintenance operations. For example, inadequate shoulder widths may require maintenance personnel to shut down a lane to perform their duties.
Including maintenance personnel in the design process can help designers identify many maintenance issues that they may not be aware of. There are two ways this can be achieved. First, during the design phase, the project team should invite maintenance personnel to design meetings where they can provide input on design aspects. Input from maintenance personnel on roadside features such as noise walls, median barriers, and ITS device locations should be considered a priority in the design process.
Second, agencies should include processes or checklists in design manuals to obtain sign-off on plans from their maintenance division. Maintenance personnel should comment on issues that relate to snow plowing operations, barrier selection and placement, impact attenuator selection, signal systems and ITS infrastructure, landscaping, median crossovers/turnarounds, shoulder width, and culvert treatments, among others.
Table 10 identifies elements to consider during design that can impact maintenance operations. It also shows potential opportunities for designers to structure their roadway design (or redesign) to allow for more cost-effective implementation of maintenance strategies in the future. Some of these design considerations would apply to multiple strategies.
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34 FHWA, Freeway Management and Operations Handbook, Section 1.1 "Scope of Freeway Management and Operations," June 2006. Available at: http://ops.fhwa.dot.gov/freewaymgmt/publications/frwy_mgmt_handbook/chapter1_01.htm#1-1. [ Return to note 34. ]
35 FHWA, Ramp Management and Control Handbook, January 2006, FHWA-HOP-06-001. Available at: http://ops.fhwa.dot.gov/publications/ramp_mgmt_handbook/manual/manual/index.htm.[ Return to note 35. ]
36 Caltrans, "Traffic Operations Policy Directive 11-02: Managed Lane Design," 2011. Available at: http://www.dot.ca.gov/hq/traffops/systemops/hov/reference.html. [ Return to note 36. ]
37 FHWA, Managed Lane Chapter for the Freeway Management and Operations Handbook, January 2011. Available at: http://ops.fhwa.dot.gov/freewaymgmt/publications/frwy_mgmt_handbook/revision/jan2011/mgdlaneschp8/sec8.htm. [ Return to note 37. ]
38 Minnesota Department of Transportation Metro Division, Guidelines on Shoulder Use by Buses, 14 Jan 1997. Available at: http://www.dot.state.mn.us/metro/teamtransit/docs/bus_only_shoulder_guidelines.pdf. [ Return to note 38. ]
39 Jones, Greg. Design and Maintenance: A Facilitated Roundtable Discussion, Regional Workshop on the Use of Shoulders for Travel Lanes, FHWA, 3 May 2012. [ Return to note 39. ]
40 Kuhn, Beverly, Efficient Use of Highway Capacity System, FHWA, May 2010. Available at: http://ops.fhwa.dot.gov/publications/fhwahop10023/chap3.htm. [ Return to note 40. ]
42 FHWA, "Work Zone Traffic Management," Work Zone Mobility and Safety Program. Available at: http://www.ops.fhwa.dot.gov/wz/traffic_mgmt/index.htm. [ Return to note 42. ]
43 FHWA, Developing and Implementing Transportation Management Plans for Work Zones, December 2005, FHWA-HOP-05-066. Available at: http://www.ops.fhwa.dot.gov/wz/resources/publications/trans_mgmt_plans/index.htm. [ Return to note 43. ]
44 FHWA, Traffic Incident Management in Construction and Maintenance Zones, FHWA-HOP-08-056x, 2008. Available at: http://ops.fhwa.dot.gov/publications/fhwahop08056x/execsum.htm. [ Return to note 44. ]
45 National Traffic Incident Management Coalition, National Unified Goal for Traffic Incident Management Detailed Explanation. Available at: http://ntimc.transportation.org/Documents/NUG-4pp_11-14-07.pdf. [ Return to note 45. ]
46 Ibid. [ Return to note 46. ]
47 NCHRP Report 525, Surface Transportation Security Volume 1, Responding to Threats: A Field Personnel Manual, Transportation Research Board/National Academies of Science, 2004. Available at: http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_525v1.pdf. [ Return to note 47. ]
48 FHWA, Considering Security and Emergency Management in the Planning of Transportation Projects, May 2012. Available at: http://www.planning.dot.gov/documents/ConsideringSecurityAndEM.pdf. [ Return to note 48. ]
49 FHWA, Freight Benefit/Cost Study: Compilation of the Literature. February 2001. Available at: http://ops.fhwa.dot.gov/freight/documents/freight_bca_study.pdf. [ Return to note 49. ]
United States Department of Transportation - Federal Highway Administration