Sustainable Transportation Through an Integrated Planning Process

Dick Nelson

Don Shakow

Integrated Transportation Research

122 Northwest 50th Street

Seattle, Washington 98107, U.S.A.

Tel: +1 206 781-0915

Fax:: +1 206 781-0915

e-mail: dicknels@email.msn.com


This paper outlines a new approach to metropolitan region transport planning and to regional transport policy and investment decisions that supports the goal of sustainable transport. The method has been designed to assist planners in developing least-cost strategies to address congestion and declining air quality, the most critical transport-related problems in many metropolitan areas in the U.S.A. However, it could be adapted to meet the different needs of other metropolitan regions. The method is both practical and systematic, relying on a new sketch planning model to calculate costs and benefits. It is termed an integrated approach because it puts demand-side and efficiency alternatives on the table for consideration along with traditional supply-side alternatives. A preliminary real-world application of the method has been made in the central Puget Sound region of Washington State, and a strategy for cost-effective transport investments in the region has been recommended. That strategy is referred to in this paper for purposes of example.

Need for a New Regional Planning Method

Metropolitan regions in the U.S.A. facing the difficult problems of ever-increasing traffic and transport-related environmental impacts usually opt for more system capacity. Although additional capacity, especially if not complemented by other actions, will not stem the steep growth of auto trips, expensive investments in roadway lane-miles and rail transit systems continue apace. For elected officials and planners who must respond to frustrated drivers, the traditional build option provides a familiar and tangible answer if not a solution. Even then, the decision of what to build is not an easy one.

Vigorous arguments typically break out between transit advocates and highway supporters. Decision makers tend to mediate the dispute by appeasing both sides with a division of the available resources. Complicating matters further is the regional political environment with its demands that resources be distributed geographically in proportion to tax revenues collected in local jurisdictions.

Some students of the regional transport planning process doubt that it can be improved. Professor Martin Wachs succinctly summarized the dilemma: "...transport policy making is primarily a political exercise, and ... analytical approaches by technical experts are invariably less influential than the pull and tug of influential interest groups".[1]

Political and other subjective factors will not be eliminated from transport decision making. Nor should they be, since the complexity of the problem and the numerous and diverse stakeholders will inherently involve judgment and compromise. The challenge is to strike a better balance between the political and analytical dimensions.

Any improvement will be difficult until new methods and analytical tools are employed. Old methods, such as cost-benefit analysis and multi-varient analysis have not been successful.

Even the new method such as called for in the Intermodal Surface Transportation Efficiency Act, the major investment study (MIS), appears problematic. When analysis turns up evidence that none of the build alternatives will effectively reduce the growth of auto trips, decision makers are not deterred from their quest for added capacity. The governmental process is invariably a long one, and too much political capital has been expended to change direction.

A new method must meet two key criteria: 1) It must assess the non market as well as the market costs of the transport system and proposed improvements; and 2) It must be capable of searching broadly among all feasible alternatives, including non capital-intensive alternatives. The search must occur at the front end of the process, not after a decision has been made to compare a limited set of supply options and to postpone consideration of demand and efficiency options to a later time.

Sustainable Transport: Practical Definition and Achievable Goal

A practical definition of sustainable transport is needed to guide transport planning and transport policy and investment decisions at the metropolitan region level. This is the level at which most major transport decisions (in the U.S.A.) are made, and it is where the largest share of person and vehicle trips occurs and transport-related environmental impacts originate.

We define sustainable transport to be achieved when the total future discounted per capita social costs, both market and non market, related to the transport system are equal to or less than the costs in a selected reference year. Under this definition, sustainability means that increased costs are not passed to succeeding generations.

Sustainability at a regional level, then, is a measure of transports impact on all aspects of the natural and human environment. All costs are accounted for, including those costs that indicate the quality of the trip for the traveler. A principal human cost is the time spent in transport. This cost is the largest single cost after the systems capital and operating costs.

This definition will understandably differ from the operational definition at the national or global level. For example, it will not necessarily include the future costs of global warming that may be difficult to disaggregate to a state or regional level.

Although a full cost accounting system would account for the impact of transport-produced climate change, it is unlikely that this cost will be sufficiently high in most cases to affect regional decisions. Global warming costs will play a more significant role in general budget cost accounting systems at the national and international level as countries individually and collectively weigh its costs against the costs of mitigation.

These definitions are not independent, however. Every hour of normal travel time itself carries a global warming cost in the form of fuel consumed. Every hour of congested travel creates time costs and excess fuel costs, the latter translatable to global warming costs.

Eventually, a global cost accounting system may be developed. This might lead to international and national policies that mandate decisions at the regional level which effectively override the definition of sustainable transport adopted here.

Until such time, a practical, working definition is needed to guide decisions that are regionally sustainable and that contribute to global sustainability.

The goal of regional transport planning and decision making should be to minimize the future total per capita cost. It may not be possible in the short term to reduce costs from current levels, but capital investments and demand-side decisions should seek a least-cost strategy.

Achieving sustainability requires a systematic approach. Table 1 lists steps that must be part of any effort to create a sustainable transport strategy. The numbering is not meant to suggest that they must be taken in the order listed, only that each is essential to a satisfactory outcome.

TABLE 1. Steps in Creating a Sustainable and Integrated Regional Transport Strategy

1 - Inventory the drivers of decentralization and increased auto dependence

2 -Evaluate the efficiency of the existing transport system

3 - Identify the transport markets that are most amenable to change

4 - Assess the unmet needs for transport equity

5 - Define the problem(s) and assign performance goals and measures

6 - Identify all feasible alternatives: supply-side, demand-side, efficiency

7 - Account for the full costs of transport

8 - Implement a least-cost search

9 - Limit investments to the amount of social benefit produced

10 - Establish an independent technical review process with public involvement

Sustainability in the Context of Decentralized Metropolitan Regions

Any effort to devise environmentally sustainable transport solutions on a regional scale must begin with a reality check -- an inventory and assessment of the centrifugal forces that are propelling urban growth in the direction of further decentralization and higher per capita levels of vehicle trip-making. The impact of many of these factors is not properly portrayed by current regional transport demand models.  There is not space in this paper to discuss the drivers of urban decentralization and increasing automobility. We only list the principal ones that have been identified for the Puget Sound region: 1) Developable land prices that fall steeply from the center to the periphery of the region; 2) Restructuring of the economy from heavy-industries to services; 3) The changed demographics of the work force -- more women working outside the home and more multiple-worker families; 4) The low operating cost of personal vehicles, including the declining real cost of fuel; 5) An extensive road infrastructure -- that expands with new development -- with sufficient capacity to adequately meet demand except for peak periods; 6) Free or low-cost parking that accompanies most development; 7) Pervasive single-purpose land use patterns; 8) Extensive physical impedances to non-motorized travel; 9) The explosion in the diversity of human activity and opportunity devoted to shopping, out-of-home dining, and recreation; and 10) The revolution in communication technology that allows work to be done remote from a central workplace. 

Decentralization does not necessarily mean that sustainable transport solutions will be more difficult to devise. It does mean that traditional solutions, such increased capacity in the form of high-occupancy vehicle lanes and major fixed-guideway transit systems, may have little desired effect on an auto-dominant transport system unless they are carefully coordinated with growth and supported by governmental policies.

Use the Existing Transport System More Efficiently

The second step is to assess how efficiently the existing system operates and identify opportunities for improvement. A close examination of the current transportation system in the Puget Sound region, both the roadways and the vehicles that run on them, indicates that it operates it in a very inefficient manner.

--Private and Public Vehicles Have Enormous Unused Capacity

There are roughly 1.5 million empty seats in private vehicles driven to work in the region during the morning commute period. Average vehicle occupancy is 1.1 persons per vehicle. The transit system also has large underutilized capacity. For example, during the afternoon peak period only 56 % of available seating capacity is utilized on buses outbound from the Seattle central business district. The average system load is approximately 13 riders on a bus with 53 seats.

--High-Occupancy Vehicle (HOV) Lanes Have Significant Potential Capacity

The most heavily used HOV lane segment in the region, on Interstate 5 in north Seattle, moves 5,000 persons per hour. Most vehicles using the lane are 2-person carpools. In several other metropolitan areas, HOV lanes carry much higher numbers of buses in peak periods and, as a result, deliver more persons per hour. An HOV lane on the Shirley Highway (Interstate 395) between Northern Virginia and Washington, D.C., carries 9200 persons per hour.

--Unused Roadway Capacity Exists Even in Peak Periods

Vehicle loads on the regions roadways vary widely with time of day. Even in peak periods capacity is available, and congestion would be less if some commuters slightly adjusted their work schedules and traveled either before or after the peak time.

Identify Transport Markets Amenable to Change

The third step is to identify the components of the transportation marketplace that are most amenable to change. The proposed strategy for the Puget Sound region focuses on commute trips because they contribute the greatest amount of congestion and appear to be most amenable to mode shift. Work trips, in contrast to other trips, have fewer destinations. Commuters who shift to transit and ride sharing, in response to government and employer actions that reduce personal travel costs, may consider different modes for other trips.

Although commute trips are just 30 percent of all trips in the peak morning and evening commute periods, they constitute a much larger fraction of the vehicles on major roadways during these periods. Survey data from Southern California indicate that at least 70 percent, and perhaps as much as 90 percent, of vehicles using freeways in the morning commute period are headed from home to work or to a work-related destination. (Some of these trips may involve one or more stops for other purposes.) This implies that a significant mode change for workers would have a positive impact on congestion.

Congestion occurs outside the commute periods during weekdays on some roadway segments, and is obviously caused by people taking trips for a range of purposes. Serious congestion also develops on weekends as people travel for purposes of shopping or recreation. Since our choice of mode tends to be habitual -- if we use our vehicles for work trips we use them for all of our travel -- a change in work trip mode may help change general travel habits and have an indirect effect on congestion that occurs at times other than during commute periods.

Assess the Need for Transport Equity

The fourth step is to identify equity issues. Equity should primarily mean a reasonable level of regional accessibility for transit-dependent populations. It might be defined in terms of a specific market, such as the work trip. For example, access to jobs in an increasingly decentralized metropolitan region can be difficult for some if their ability to commute or relocate is restricted by cost. Equity should also include consideration of the tax sources used for financing. More often equity has come to mean a distribution of transport investments to political jurisdictions or geographic areas. In the Puget Sound region, transit planners divided the region into five subareas that were promised a division of funds in rough proportion to taxes paid.

Although taxpayers expect a return on their investment, regionally effective solutions become far more problematic when the revenue pie is divided in this manner.

Define the Problem and Decide How to Measure Success

The fifth step is to clearly state the problem(s) and decide how success should be measured. Problem statements should be explicit, not general, and performance should be amenable to direct measurement. Performance should be measured in ways that meet both governmental standards and public needs and wishes.

The traveling public in the Puget Sound region presently perceives and understands transport benefits in terms of congestion relief. While congestion reduction was invariably mentioned as a key goal in official planning documents in the region, it was not designated a measurable outcome.

A primary performance measure should be devised which indicates how regional travel time delay is affected by the recommended strategy. Other secondary benefits should be identified and measured that are of interest to stackholder groups. A clear additional benefit is how equitably people across the region share in the primary benefit of congestion relief. For some travelers, having more travel choices, especially safe non-motorized modes, is a benefit. Money that is freed up when a cost-effective regional solution is found, would also constitute a benefit. It could be applied to local transport problems or to important social purposes. Other measurable benefit indicators include: reductions in health impacts, environmental damage, and accident costs, as travelers shift to transit, ride share and non-motorized modes.

Survey All Feasible Supply and Demand-Side Alternatives

The next step involves the identification of all feasible alternatives, their costs, and their performance characteristics. This means that efficiency improvements and demand-side alternatives -- including incentives, disincentives, and regulatory mandates -- must be included along with supply-side alternatives. Integrating diverse alternatives creates synergistic benefits, for example when commuter alternative travel mode allowances are combined with employee parking supply restrictions or higher parking costs. It also forces planners to adequately fund the cost of demand side alternatives, which may be considerable. The integrated planning process in the Puget Sound region referenced in this paper identified almost two hundred distinct efficiency, supply and demand-side alternatives.

Base Decisions on Sound Economic Principles

The next three steps involve establishing economic principles and measures on which to base the transport investment decisions. A region needs a yardstick, a rational basis, for deciding how much should be invested in transport beyond maintenance, preservation and new transit and roadway capacity to serve population growth. Obviously, investments that enhance mobility above this level will be limited by public support for other priorities. But what is a reasonable level of public investment in transport? The following principles should guide planners:

--Account for the Full Costs of Transport. Full cost means the indirect costs as well as public and private "out-of-pocket" expenditures. Indirect costs include the time costs of travel and the environmental costs of transport, such as the health impacts of air pollution.

--Implement a Least-Cost Search for an Integrated Solution. All feasible transport alternatives should be compared and an integrated set of alternatives should be selected based on the principle that the benefit produced is achieved at minimum cost; alternatively, that a given investment leads to a maximum amount of benefit. A computer sketch planning model derived from extensive experience in energy planning has been developed and is available for this analysis.[2] It has been described in recent reports.[3-6]

--Limit the Transport Investment to the Value of Benefit Produced.

Public transportation investments should be constrained to the value of the social benefits produced. For example, the estimated cumulative increase in "normal" (recurring) congestion costs over the next 10 years in the Puget Sound region based on a travel demand forecast is $5.1 billion. Thus the region could reasonably spend up to this sum on an integrated solution that eliminated all growth of congestion over the current level.

Establish an Independent Review Process and Effective Public Involvement

Planners, as Wachs has pointed out [7], often find that their professional objectivity is in conflict with their obligation to serve the interests of an employer. When a transport agency is charged with developing a regional transit system, it can be anticipated that transport planners will produce studies that portray costs and benefits in the most favorable light. Given the political environment, even other planners, who have different opinions, may not be free to express their views publicly. A case in point is a benefit study done internally by the Puget Sound Regional Transit Agency for its regional transit plan. Although the study found abundant economic benefits, the plan was described by a chief regional planner as leading to a situation in which ...amortized costs would soon be overwhelmed by financing the annual debit of operation. This opinion was expressed after the planner left his position and the region.

Useful transport planning analysis requires independent review accompanied by effective public involvement. The technical review process should be established at an early stage, and should involve review and comment at each step, but especially on the alternatives selected for analysis, system ridership forecasting methods and results, financial assumptions, and benefit calculations. The public, which is customarily asked to comment before and after the planning process has run its course, should be allowed to interact at each step of the technical review.

Results of Applying the Method to the Puget Sound Region

The method (except for step 10) was used to design a cost-effective, integrated strategy as an alternative to a rail transit system proposed for the Puget Sound region. The strategy, which would cost about $4.6 billion over the next 10 years, would produce greater benefits (reduced growth of congestion, improved air quality, greater equity) at less cost than the proposed rail system. It highlights incentives to get people out of their cars and into HOV modes. The strategy recommends the region:

--Create a "seamless" regional HOV lane network. The freeway HOV lane network would be completed and connected to new arterial HOV lanes serving activity centers and transit stations. Express bus service using the network would be expanded and feeder bus service to the network would be added.

--Provide incentives to ensure that the HOV network is fully used in commute periods. Incentives, including monetary payments, would be used to encourage shifts to transit, vanpooling, carpooling, and non-motorized modes, and to spread demand to non-peak hours.

Recommended incentives include: 1) Employer tax credits based on the number of employees who shift to alternate (non SOV) commute modes; 2) Cash-out of employer-subsidized parking; 3) Preferential parking for ride-share vehicles at work sites; 4) Increased subsidies for public van pools; 5) A region-wide guaranteed ride home service; and 6) A real-time traveler information system. Under the recommended strategy, incentives are budgeted at $1 billion, approximately one-fourth the total cost.

--Take actions to foster the long-term development of strategy. Specifically: 1) Initiate small-scale tests to assess the benefits and costs of innovative transport systems such as bicycle commuting and personal rapid transit; 2) Create a regional model to determine congestion costs; 3) Modify the governance of transport to better enable planners to develop integrated strategies; 4) Create a better data base for the drivers of trip demand and to evaluate the performance of investment alternatives; 5) Increase by a factor of 10 the ride matching data base; and 6) Work with other regions to amend federal tax law that favors SOV commuting.


The authors wish to thank Emory Bundy, Mike Ferro, John Niles, and Jerry Schneider for their many helpful suggestions during the course of the work described in this paper.


Martin Wachs, Transportation Research, Vol.27A, No.4, p.337, (1993).

Edward Sheets and Richard Watson. Least Cost TransportationPlanning: Lessons From The Northwest Power Planning Council. Seattle, Washington: University of Washington Institute for Public Policy and Management. January 1994.

Dick Nelson and Don Shakow. Applying Least-Cost Planning toPuget Sound Regional Transportation, Phase I: Development of the Conceptual Model for a Least Cost Transportation Planning Process. Seattle, Washington: Institute for Transportation and the Environment, February 1994.

Dick Nelson and Don Shakow, Applying Least-Cost Planning toPuget Sound Regional Transportation, Phase II: Development of a Prototype Least Cost Planning Model and its Initial Application to the Puget Sound Region. Seattle, Washington: Institute for Transportation and the Environment, December ,1994.

Dick Nelson and Don Shakow, Least-Cost Planning: A Tool for Metropolitan Transportation Decision Making, Transportation Research Record, #1499, Transportation Research Board ,Washington, D.C.

Dick Nelson and Don Shakow. A Cost-Effective Strategy forPuget Sound Transportation. Seattle, Washington: The Institute for Washingtons Future. September 1995.

Martin Wachs. When Planners Lie with Numbers, AmericanPlanning Association Journal, Autumn 1989, pp. 476-479.

Return to the Least-Cost Transportation Planning index page

Last modified: June 1, 1996