Planning, Development, and Implementation
Transportation Demand Management (TDM) is the art of modifying travel behavior, usually to avoid more costly expansion of the transportation system. TDM is not a panacea, but it can help ease some transportation problems. TDM requires the cooperation of many actors, who may include developers; landowners; employers; business associations; and municipal, county, regional, and state levels of government.
This article reviews new TDM organizational forms, including transportation management associations, trip reduction ordinances, and negotiated public-private agreements. More flexible approaches appear to work best. TDM evaluation is difficult, because reductions in trip generation rates, i.e., relative changes in travel demand, are not easy to measure. Evidence suggests that TDM can be applied in a wide variety of situations, with equally variable, and sometimes quite good, overall results. TDM strategies that often have proven to be effective include on-site employee transportation coordination, parking management provisions, and alternative work schedules (Ferguson 1990).
Evolution
TDM is a natural outgrowth of transportation systems management (TSM), itself a modification or expansion of the traditional urban transportation planning process. TDM developed during the 1980s as a response to increasing traffic congestion and air pollution problems, with more of a travel behavior and private sector orientation than its predecessors. Current issues facing TDM and its practitioners include ease of implementation and political acceptability, or the lack thereof, as the case may be (Ferguson 1999).
Three Faces of Eve
The political acceptability (A) of public policy measures correlates positively with program effectiveness (E) and negatively with program cost (C) and other obstacles to implementation (I) under normal circumstances. Ferguson (1991) observed that the political acceptability of many demand management strategies seemed to correlate negatively with implied program effectiveness. Engineers, economists, and planners each have their own unique professional standards. Increased effectiveness is the primary goal of engineering. Improved efficiency is the generally accepted standard in economics. Process issues are of vital concern in planning. A review of the literature indicates few studies that rate demand management strategies in terms of all four variables of interest (A, E, C, and I) simultaneously. Three relevant studies were identified: one each by an engineer, an economist and a planner. Raw data, regression results, bivariate correlations, and model output reveal that two of the three studies support the Ferguson hypothesis. The other supports a more traditional public policy model. E is the most influential variable in the engineer’s data. C is the most influential variable in the economist’s data, while I is the most influential variable in the planner’s data. These revealing results suggest the subtle manner in which professional training and experience may alter perceptions of transportation policies and programs in professional practice (Ferguson 2001).
TDM is a program of information, encouragement and incentives provided by local or regional organizations to help people know about and use all their transportation options to optimize all modes in the system – and to counterbalance the incentives to drive that are so prevalent in subsidies of parking and roads. These are both traditional and innovative technology-based services to help people use transit, ridesharing, walking, biking, and telework (Arlington Mobility Lab).
TDM is a layer of policies, programs, information, services, and tools that work with the transportation infrastructure and operations to support the use of sustainable modes for all trips. Together, TDM strategies result in reducing the need to rely on single occupant vehicle (SOV) trips and can help reduce households’ need for car ownership. The goal of TDM is to help households, employees, and visitors make more of their trips on transit, by bike or on foot, or in shared vehicles like taxis and carshare cars. Not only do TDM strategies reduce congestion, they improve the utilization of existing services and can result in cost savings to companies and individuals (San Francisco MTA).
Since 2010 transportation professionals have suggested that TDM is widely misunderstood simply as a collection of vaguely related initiatives, and that this misunderstanding is constraining the true potential of the concept. TDM practitioners have found that TDM is far more effective when framed as a philosophical approach which over time becomes a cornerstone of sustainable urban transport systems. A new paradigm in transport planning, internationally recognised as TDM, appears to be emerging which embraces concepts such as “mobility management” and “active travel management” under its umbrella.
Crucial to the delivery of a sustainable urban transport system is integrating the TDM philosophy into urban transport planning, as well as the daily management and operation of transport services and infrastructure. It appears that managing travel demand has largely been compartmentalized as a set of “soft measures” to promote sustainable travel options or programs to promote and offer shared ride arrangements. Demand management means different things to different disciplines. For example: to Information Technology (IT) specialists, managing demand is new technology to provide information; to operations managers, managing demand is controlling the flow onto highways; to economists, it is pricing the system to find equilibrium with capacity; to marketers, it is promoting innovative campaigns; and to many policymakers TDM remains a largely unknown entity.
The concept has become confused as each discipline has tried to mold the concept to their set of tools. This “silo” thinking inhibits the kind of policy integration that is needed to develop a sustainable urban transport solution strategy. There remains much confusion as to what a sustainable transport system would comprise. It is helpful therefore to consider different approaches to sustainable transport along a spectrum of viewpoints, ranging from weak to strong sustainability. Generally efforts to address the impact of transport on climate change to date have been largely focused on technology. The impact of this technological-led approach has been very limited in the transport sector. TDM has the potential to move the transport sector from a position of weak to strong sustainability by combining behavior-change with technology improvements.
In this context, TDM may be understood as a much broader concept. Implicit in the use of the term is the assumption that it is accompanied by the implementation of sustainable mobility, introduction of full cost pricing and organizational or structural measures to ensure a broad range of complementary interventions work effectively together to realize the benefits of sustainable transport. It is the unifying philosophy of TDM, not specific measures associated with it, that underpin the policy objective of a more sustainable system of transport. This philosophy of managing demand accepts that meeting unfettered demand for travel is impractical and that therefore the system needs to be managed. That demand for travel needs to be managed by:
- Expanding the supply and availability of (more sustainable) alternatives;
- Controlling demand for the use unsustainable modes;
- Providing incentives and rewards for undertaking sustainable travel habits; and
- Imposing full-cost pricing on the use of the automobile.
The Meaning of TDM in the Context of Decision Space
Bicycling in the Netherlands
Employee Commuter Benefits
Keech Ballard 