7. Integration of TDM at the Corridor Planning Level
While TDM has historically been focused on mitigating traffic at localized trip generators (e.g., large employment sites, new developments, etc.), it is increasingly being applied to congested corridors, including interregional corridors that cross county and state boundaries. This is because TDM has focused on the commuter travel market, which, in turn, is associated with peak period congestion on key highway facilities. In fact, one of the nation's first ride-matching services was offered by a radio station attempting to find solutions to traffic congestion on Boston's Southeast Expressway and other key facilities in 1973. Today, TDM is part of an overall scheme to better and more efficiently manage the operations of congested highways. TDM in highway operations is needed because, on a day-to-day basis, the operators of our highway systems cannot add capacity to meet changing conditions, but they work to manage the daily demands placed on our highways. This can be accomplished by offering travelers more and better travel choices.
Managing how many vehicles are on a given facility at any one time, via demand management techniques, can influence the effective capacity of the roadway and maintain traffic flow. This is the premise of the now popular "rice experiment" promoted by Washington State DOT.122 The rice experiment showed that by modulating the rate at which vehicles entered the system (in the experiment, rice through a funnel), travel times can be increased or at least made more reliable.
At a smaller scale, this is the function of ramp metering. However, if travelers can shift their travel time, location, route or mode, fewer total vehicles may be using the facility during peak, congested periods.
From a planning standpoint, TDM needs to be integrated into the planning process to maximize the ability to reduce peak period demand. This is most relevant when considering major improvements to a corridor, so that the benefits of the improvements can be extended by lowering overall demand levels. This might involve strategies to price the facility, provide preferential treatment for HOVs, integrate traditional TDM programs for adjacent employment centers and other major traffic generators, improve facilities/operations of facilities parallel to the new corridor, or manage access to the corridor or land development adjacent to the corridor. But it is also important to explicitly consider TDM strategies, linked to a corridor, when planning for the ongoing operations of a facility with the goal of maximizing efficiency. This might be as simple as including all travel choices in the traveler information provided or linking regional ridesharing providers to the TMC.
7.1 What Plans Should TDM be Included in?
The integration of TDM into corridor planning efforts is quite broad and can involve organizations at the state, regional, and local level. Some interregional corridor planning activities can even cross state boundaries. Some of the corridor-level plans that might involve TDM integration are enumerated in Table 7.1.
There are two significant decisions related to integrating TDM into the corridor planning process - timing of the integration and scope or breadth of the TDM strategies considered.
In terms of timing, TDM strategies, and the general philosophy of balancing demand and supply solutions, should be considered at the start of the corridor planning process. Too often, TDM is considered almost an afterthought – a means to mitigate potential impacts of highway construction or as part of a list of supportive measures that are not truly integrated into the future operation of the facility.
Regarding scope, TDM strategies are often considered in a narrow or piecemeal fashion. The full set of TDM strategies, or travel choices, need to be included in corridor planning efforts. In some cases, the only "alternative" mode considered is transit and in other cases only traditional commuter-based TDM is considered. Time, location, and route choices should be considered in addition to mode choice. The Congestion Management Process is one framework that should help address this deficiency in the link between demand management and corridor solutions. As another example of this disconnect, the synergistic benefits of packaging TDM strategies are sometimes overlooked. For example, efforts to plan HOT lanes assess the impact of pricing on behavior change and facility operations, but often do not include provisions to support HOV services to achieve maximum throughput of the HOT facility.
Finally, involving all key stakeholders in the corridor planning process is important as well. These potential stakeholders are enumerated below, but critical participation is needed from those who will ultimately operate the facility and related services. This includes participation from day-to-day operators and service providers, such as the TMC, other traveler information providers, and service providers, such as transit operators, vanpool providers, and bicycle user groups.
7.2 What Is Your Capability with TDM at the Corridor Planning Level?
This desk reference will be utilizing the guidance based on different levels of existing experience with TDM and transportation planning. Table 7.2 provides examples of how planning agencies might integrate TDM into their corridor planning processes. This should assist users in determining the nature and location of key guidance within this section. Three levels of TDM integration are presented: ad hoc, defined, and optimized. As explained earlier in this document, these levels correspond to the Institutional Capability Maturity Model proposed by FHWA in its Guide for Improving Capability for Systems Operation and Management.123
Agencies with minimal experience in integrating TDM (ad hoc level) into their corridor plans and policies might only be viewing TDM as a mitigation strategy during reconstruction or seeking to use it to improve livability since there might be need to address congestion or air quality. At the next level (defined), an MPO might include TDM in most plans and policies as a means to increase travel choices and meet certain policy objectives, such as clean air or congestion reduction. In this case, TDM is likely one element of the overall plan. Finally, when TDM becomes optimized (Level 3), TDM may become a central focus of the entire plan if the MPO's policy board adopts an overall "philosophy" of managing demand and encouraging sustainable transport.
Table 7.2 provides specific examples of how an MPO might work to integrate demand management into regional transportation planning efforts at different levels of capability. This matrix is intended to assist the reader in determining where his or her organization fits in terms of the capability levels described above. Once the reader has determined his/her capability level and identified the critical step on which he/she is focused, specific actions to move from one level to the next are suggested in the next section.
7.3 Actions to Move Corridor Planning Process from Level 1 to Level 2
Several specific actions can be suggested to move an agency's corridor planning process from Level 1 (ad hoc integration of demand management) to Level 2 (defined integration). For each action, a rationale is provided, an explanation of how to implement the action, and examples are given where available. Table 7.3 indicates the relative ease or difficulty of implementing each action.
Action 1 – Establish guidance on how to and benefits of integrating TDM into corridor planning at the very beginning
Example – Most guidance related to integrating TDM into corridor planning comes from highway reconstruction efforts. NCHRP Synthesis 273, Project Development Methodologies for Reconstruction of Urban Freeways and Expressways, provides guidance on the role of TDM in mitigating the traffic impacts of reconstruction.124
Action 2 – Determine organizational and inter-organizational responsibilities for TDM in corridor planning
Example – When plans were developed to make operational improvements on the SR 520 corridor in the Puget Sound, TDM strategies were included from the beginning. Improvements include active traffic management, tolling, transit improvements, bicycle facilities, as well as vanpool and telecommute promotion among area employers and TDM agents. This was due, in part, to the fact that Washington State DOT has a very active TDM program and that TDM implementation agents, such as Seattle Metro and area TMAs, were involved from the beginning.
Action 3 – Developing SMART objectives for TDM
Example – The Washington State 2006 CTR Efficiency Act continued a state mandate that goes back to 1991. Cities and counties are able to set their own specific goals and targets for employee commute trip reduction, as long as they met the minimum state targets of a 10% reduction in single occupant commute trips by 2011 to address congestion and a 13% reduction in VMT to address GHG emissions. In the first three years of the program, 154 million VMT have been reduced at over 1,000 worksites representing over a half a million commuters. This is estimated to have reduced highway delay by 8% in the Central Puget Sound region and almost 70,000 metric tons of GHG statewide. While the state legislation behind the CTR Efficiency Act was a major policy effort, the need for and ability to set quantifiable targets was fairly straightforward. Another example involves the 1996 Boulder, Colorado, Transportation Management Plan, which identified 10 multimodal corridors and improvements for all modes of travel along them. As these corridors carried a majority of the trips in the community and linked important activity and commercial centers, maximizing their efficient trip-carrying ability required improving the relationship between the multimodal transportation system, land use, and design along these corridors.
Action 4 – Identify concrete performance measures for TDM
Example – The State of Florida has developed and adopted multi-modal LOS standards for comparison among and between modes and projects. FDOT's Quality/Level of Service Handbook of 2009 provides a methodology and analysis tools to develop and use multimodal performance measures for car, transit, bike, and walk travel for a given urban corridor.125
Action 5 – Create means to translate TDM performance metrics into highway operations metrics
Performance indicators more appropriate to TDM include:
The measure that likely comes closest to linking the two disciplines is person throughput. Knowing vehicle occupancy, including transit, can help planners understand the efficiency of the facility in moving travelers, not vehicles.
Example – The example shown in the action described below illustrates one means of translating TDM effectiveness, in terms of mode shift, to reductions in delay. In this case, the mode shift impacts documented for the CTR law among employers in downtown Seattle are graphically shown as changes in travel time on I-5.
Action 6 – Draw upon existing tools to improve TDM modeling and analysis
Example – Chapter 9 includes a description of several tools aimed at allowing for the quantification of TDM impacts for various strategies and packages of strategies. This includes the FHWA TDM Evaluation Model and the TRIMMS available from the CUTR (see more discussion in Section 9 on Tools and Techniques for Evaluating TDM).
However, in terms of tools to evaluate the impact of TDM on corridor operations, CUTR has developed a means to graphically display the temporal and spatial distribution of trip reduction, due to TDM, on a given facility, using CORSIM.
Action 7 – Integrate TDM into all Scenarios for Corridor Improvements
Example – A paper summarizing the use of TDM in MIS conducted by the North Central Texas Council of Governments concluded that TDM and TSM can effectively complement major transportation investments. These strategies promote the use of transit and alternative commute modes, as well as improves transportation system performance. Both TDM and TSM strategies are relatively low-cost, quick-implementation transportation programs and projects, which should not be overshadowed by proposed major transportation improvement(s). Since an MIS is an intensive and comprehensive study of transportation alternatives in a travel corridor, this study process provides an excellent opportunity to explore the implementation of these low-cost, quick-deployment transportation strategies.126
Action 8 – Seek means to include traditional ridesharing and incentives into corridor plans
Example – During the 2002 reconstruction of U.S. 101 over the Cuesta Grade in San Luis Obispo County, CA, several demand management strategies were implemented to mitigate the impact of the roadwork on commuters. These measures included additional peak period bus service in the corridor, vanpool subsidies, and subsidized fuel cards for carpools. An evaluation of the impact of the demand management program concluded that the combination of measures eliminated 310 cars per day from the facility and about 8,000 miles of vehicle travel by raising overall vehicle occupancy from 1.206 to 1.266. The daily cost to take each car off the road was estimated at $7.50. These reductions contributed to an overall perception by the traveling public that the reconstruction project was less disruptive than originally feared.127
Action 9 – Include TDM elements in overall corridor project funding
Example – The Colorado DOT included a comprehensive TDM program in its T-REX project to reconstruct I-25/I-225 and expand light rail. TDM funding was included in the public involvement budget, with specific funds for targeted traveler information, transit and vanpool incentives, and local coordination and outreach.
Action 10 – Strengthen TDM performance evaluation and monitoring methods and means to report impacts
Example – The evaluation of HOT lane projects often includes data that relate TDM to highway operations, such as vehicle occupancy, person throughput, alternative mode utilization, etc.
7.4 Actions to Move Corridor Planning Process from Level 2 to Level 3
Several specific actions can be suggested to move a corridor's planning process from Level 2 (defined integration of demand management) to Level 3 (optimized integration). Table 7.4 highlights the relative ease or difficulty for each action in moving from Level 2 to Level 3.
Action 1 – Determine range of travel markets that can be influenced by TDM
Example – An FHWA guidance document entitled "Mitigating Traffic Congestion: The Role of Demand-side Strategies" enumerates many travel markets or applications for TDM, beyond traditional commuters.128 These venues include: schools and universities, recreation and tourism, special events, hospitals, and airports.
Action 2 – Determine whether TDM is an overall operating philosophy or mitigation strategy
Example – FHWA is developing a new program entitled "Active Transportation and Demand Management" (ATDM), which is defined as the dynamic management, control, and influence of travel demand, traffic demand, and traffic flow of transportation facilities. Through the use of available tools and assets, traffic flow is managed and behavior influenced in real time to achieve operational objectives. ATDM is not a set of specific strategies; rather it is an over-arching philosophy for managing a facility through demand management and dynamic traffic management.
Action 3 – Train corridor project managers on TDM
Example – As noted in the state-level section of this document, Colorado DOT has developed tools to assist its planners and project managers, as well as local government and business, with TDM implementation, including The TDM Toolkit and the TDM Corridor Projects Study (see T-REX example above), which offer a complete list of strategies with TDM successes throughout Colorado and the U.S.129 However, sometimes the skill mix and training of project managers can work to restrict innovations, such as TDM. In fact, the Dutch Ministry of Transport has implemented a program to broaden the types of professionals who are assigned as major infrastructure project managers, retaining not only engineers, but economists, psychologists, social scientists, and anthropologists.
Action 4 – Develop new partnerships in key corridors
Example – Corridor coalitions have been used extensively for urban segments (U.S. Highway 169 Corridor Coalition) and interregional efforts (I-95 Corridor Coalition). These efforts bring all levels of government as well as the private sector to the table to plan and implement corridor improvements. The U.S. Highway 169 Corridor Coalition's mission is "Working together to enhance safety, reduce congestion and maximize economic development along the U.S. Highway 169 interregional corridor. " This includes freight, intercity, and commuter travel.
Action 5 – Set longer term objectives for TDM
Example – The UK Department for Transport developed a concept entitled "Integrated Demand Management" (IDM), originally designed to incorporate demand management into comprehensive corridor improvement plans and projects. The IDM concept is being applied to the reconstruction and widening of the M25 motorway around London. The Highways Agency describes IDM as "a holistic approach based upon making best use of the existing road-space and locking in the benefits of widening. " The philosophy behind IDM is to maximize the efficiency of the facility using ATM and to maximize the effective life of the improvement by reducing overall demand for its use.
Action 6 – Develop corridor performance measures tied to person throughput
Example – The HOT lane demonstration project on I-15 in Salt Lake City, UT, revealed that the Express Lane (open to carpools, vanpools, buses, motorcycles, and paying solo drivers) carried almost twice as many persons as the average general purposes lane during the PM peak period.131
Action 7 – Develop procedures for considering demand management strategies prior to other, more capital intensive alternatives
Example – One example of the full institutionalization of TDM into the planning process comes from Sweden. In 2002, the Swedish National Roads Administration adopted the "four stage principle" that requires planners and engineers to evaluate options in the following order:
Planners are, therefore, required to consider and rule out demand management before they can consider infrastructure improvements.132
Action 8 – Use TDM as a means to reduce need or delay to expand road capacity
Example – In a few cities, the TDM philosophy is fully embraced and the result is an overall reduction in car travel. In Lund, Sweden,133 and Arlington, Virginia134, reductions in VMT and vehicle volumes have been observed and documented in line with implementation of aggressive TDM programs. Arlington County, Virginia, has documented a reduction (12-16%) in traffic levels on several key arterials concurrent with considerable growth in public transport ridership (38%) and demand management success with area employers and institutions.
Action 9 – Develop new tools/approaches to incorporate all travel choices into the analysis process
Example – The traditional four-step travel demand modeling process can be used to evaluate TDM strategies that can be analyzed in terms of time and cost variables. However, many off-model tools have been developed to analyze congestion pricing strategies, bicycle and walk strategies, and other strategies that cannot be expressed in terms of time and cost indicators. As mentioned above, a good discussion of the means to incorporate TDM into regional travel demand models is provided by CUTR in a report entitled "Incorporating Assumptions for TDM Impacts in a Regional Travel Demand Model." This approach, which was developed for WSDOT, includes a specific TDM Assessment Procedure that uses the CUTR TRIMMS model and processes resulting TDM impacts through standard trip tables.135 In fact, the use of the TRIMMS model itself (discussed in Chapter 9) to perform cost/benefit analysis for TDM strategies could represent a significant movement toward mainstreaming TDM integration.
Action 10 – Include active demand management to integrate TDM into corridor solutions
Example – The ATDM program, being developed by FHWA, provides examples of four types of "active demand management" strategies to complete active traffic and active parking management. These active demand management strategies include: dynamic ridesharing, on-demand transit, dynamic pricing, and predictive traveler information.136
Action 11 – Include TDM as a key element to reducing overall, long-term demand
Example – As cited in the last section on metropolitan-level planning, the TSM&O plan in the Portland region devotes almost as much funding to TDM as to capital and efficiency improvements.
Action 12 – Adopt or develop a standardized approach to reporting TDM performance
Example – The MAX-SUMO monitoring and evaluation approach developed in Europe is easily adaptable to the U.S. experience for many TDM strategies. The methodology is described in Chapter 9.
7.5 Best Practice Examples: Corridor-Level TDM Integration
Two types of best practice examples are provided here – one focused on TDM and highway reconstruction in Colorado and another focused on planning for TDM and innovative corridor operations (HOT lanes) in Virginia.
TDM strategies are increasingly being integrated into highway reconstruction projects and therefore are an integral part of the planning process. One of the most comprehensive examples comes from the T-Rex project in the Denver area (Figure 7-1), the reconstruction of I-25/225 and extension of light rail (completed in 2007).137 During reconstruction, a temporary HOV lane was added to provide a travel time advantage to carpools, vanpools, and buses. TDM was built into the public outreach component of the project at an early stage. Some $3 million was dedicated to TDM to support the following:
Figure 7.1: Denver T-Rex I-25/225 Reconstruction
Colorado DOT noted that the TDM activities reduced the risks associated with the reconstruction project and that follow-up surveys showed that travelers were very supportive of the TDM strategies. CDOT now plans to build TDM into all major reconstruction projects as a matter of procedure.
Many HOT lane projects have provided new or improved transit services as an alternative to paying the toll. However, the conversion of an HOV facility to HOT operations (priced use of excess capacity by drive alone travelers) should consider means to maintain or grow HOV use in order to maximize the operational efficiency and person throughput of the facility. Some plans have been largely based on the assumption that HOV will recognize the benefits of free travel in the HOT lane and continue to share rides. However, in some cases, the vehicle occupancy level is being raised to 3+ occupancy in order to create capacity to sell, creating the need to maintain existing HOV levels so as not to create new drive alone modes.
The Virginia Department of Rail and Public Transportation undertook a planning process to assess the most cost effective use of HOT lane revenue for transit and TDM in order to maintain and enhance HOV utilization as part of planning for the I-95/I-395 HOT lane project in northern Virginia, from Arlington to south of Fredericksburg.138 An I-95/I-395 Transit/TDM Technical Advisory Committee was created to study, analyze, and plan for the best mix of transit and TDM strategies to maintain and grow alternative modes use while introducing HOT lane operations. Two stated objectives for the planning effort were to:
This is a departure from some plans, which largely assume HOV use to be constant and seek ways to capitalize on unused capacity, by seeking ways to grow HOV and transit use within the context of HOT lane operations. The plan outlines many new and enhanced transit services and many enhanced TDM measures, including: capital assistance for vanpools, enhanced Guaranteed Ride Home programs, financial incentives for vanpools and carpools, rideshare program operational support, TDM program marketing support, and telework program assistance.
122 Washington State Department of Transportation Rice Experiment, available at http://www.wsdot.wa.gov/Traffic/Congestion/Rice/Default.htm
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United States Department of Transportation - Federal Highway Administration