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Traffic congestion is slowing America down. In cities large and small, from the east coast to the west coast, traffic congestion is steadily getting worse each year. A larger percentage of the nation’s roadway network is congested, more severely and for longer portions of each day, than ever before. In 1982, the average person living in one of the country’s 75 largest cities faced seven hours of travel delay per year. By 2001, that figure had shot to 26 hours of delay per year, and the most severely congested periods of the day – once known as the “rush hour” – stretched to cover nearly six hours of each day. By 2001, the severity of peak-period congestion also intensified, with the average “rush hour” trip taking nearly 40% longer than the same trip at other times of the day (TTI, 2003).

The impacts of traffic congestion are far-reaching – impacting individuals, families, businesses and communities. The Texas Transportation Institute (TTI), at Texas A&M University, calculates that the country’s “congestion invoice” amounted to nearly $70 billion in 2001 – the byproduct of 3.5 billion hours of delay and 5.7 billion gallons of excess fuel consumed in congestion-related delays. These costs directly affect individuals and families, as people spend more time and money stuck in traffic. For most American households, transportation costs now account for 18% of total household expenditures. Only shelter represents a larger portion of expenditures, at 19%. The impacts on lower-income families are even more severe. For households earning between $12,000 and $23,000 per year, transportation expenses consume one in every four dollars spent (STPP, 2000).

Recognizing the growing burden of traffic congestion and the importance of efficient access and mobility, community leaders and transportation planners are actively working on transportation improvements to alleviate traffic congestion. Much needed roadway, bridge, and transit infrastructure projects – considered transportation “supply” or “capacity” enhancements – are underway across the country to mitigate travel delays and accommodate future growth needs.

As urban areas mature, however, opportunities for further investments in transportation infrastructure are often limited. Urban transportation corridors increasingly lack the physical space to accommodate more lanes. In some areas, communities voice concerns that impacts to private rights-of-way or sensitive environments outweigh the potential benefits of expanding facilities. Many areas simply lack the funds needed to pay for major roadway or transit projects. Competition for limited federal and state funds is intense, and even where needed infrastructure projects are in the planning or construction stages, project completion can still be years away.

Effectively tackling traffic congestion increasingly means employing all available strategies. New infrastructure projects – from roads to bridges to transit facilities – remain a core element of comprehensive transportation improvement programs.

Supplementing these “supply-side” investments are a broad array of “demand-side” strategies intended to make existing transportation facilities work better. Demand-side strategies are designed to better balance people’s need to travel a particular route at a particular time with the capacity of available facilities to efficiently handle this demand. Many people have attended a sporting event or a concert where everyone tries to leave the same place at the same time. While in the extreme, this is a perfect example of where travel demand exceeds available supply – and severe traffic congestion often results. The focus of demand-side strategies is to provide people with enhanced travel choices – from choices in travel mode (such as driving, using transit or bicycling), to choices in travel route and trip departure-time – and to provide incentives and information for people to make informed travel choices. For example, many sports and concert venues provide incentives for people to arrive a little early or stay a little late, essentially spreading the “peak” of the demand to travel to/from the building, reducing traffic congestion, and improving the visitor’s overall experience.

This contemporary understanding of demand-side strategies is broader in scope than prior, more traditional views of transportation demand management – or TDM. To some, the realm of demand management applications is limited primarily to encouraging alternatives to single-occupant vehicle travel for the commute to work. In practice, however, this narrow view is no longer consistent with the broad applications of demand-side strategies currently underway across the country. Today’s applications are not only limited to facilitating shifts in travel mode – they also address shifts in travel routes and travel departure-times (for all travelers, including single-occupant vehicle drivers). Today’s applications also extend beyond a focus on commute trips. At national parks, sports stadiums, university campuses, and other diverse destinations, transportation and facility managers are implementing demand-side strategies as part of coordinated efforts to reduce congestion. On bridges, and along corridors undergoing roadway reconstruction programs, demand-side strategies are helping travelers avoid congestion by utilizing alternative travel routes, travel times and/or travel modes – or by reducing the need for some trips altogether by facilitating work from home options a few days a month.

Mitigating Traffic Congestion: The Role of Demand-Side Strategies articulates a framework for understanding contemporary efforts to manage demand and improve the performance and efficiency of transportation systems. The document provides extensive examples of programs already underway in a variety of application settings, including over 25 in-depth case studies from across the country.

The in-depth case studies illustrate a handful of the many applications of demand-side strategies in place today. The case studies attempt to highlight the diversity of programs, with an effort to find examples that also provided one or more measures of program effectiveness. A few highlights from the case studies include:

• SBC Park (formerly Pac Bell Park) in San Francisco – a 41,000 seat baseball stadium – forged an access plan that integrated excellent access to existing transportation facilities (roadways, bus and rail transit, ferry services, and an extensive sidewalk network) and a comprehensive transportation management plan. With only 5,000 dedicated parking spaces available, demand-side strategies to promote a variety of mode and route travel options, along with advanced transit ticket sales and an aggressive marketing program, were key to the stadium’s success. The year the park opened, approximately 50% of baseball fans arrived in non-auto modes, over 100,000 advance-purchase transit tickets were sold, and the limited number of parking spaces were rarely full.

• CH2M Hill in Denver implemented a transportation program to improve the commute and enhance their employee recruitment and retention abilities. They designed an aggressive telework program with full-time and part-time telework options, and instituted a flextime program to better support a variety of commute options. CH2M Hill also designed the “Look Before You Leave” program, which encouraged all employees to check traffic conditions on a company intranet that centralized a variety of resources for current traffic conditions, roadway construction updates, etc. This resource encouraged employees to avoid the most congested travel routes and travel times whenever feasible. At this suburban work location, 17% of CH2M Hill employees use transit, carpool, bicycle, or telework. In 2002, the program reduced the number of miles driven by employees by over 115,000, and saved nearly 3,700 staff hours.

• Lee County Bridges crossing the Caloosahatchee River in southwest Florida are a major source of congestion and travel delay for the region. In 1997, County leaders implemented a variable pricing system for the bridge tolls which incorporated a discount for travelers crossing the bridges just before and just after the peak-periods (when using the electronic toll collection system). A 1999 survey found that this demand-side pricing system encouraged 7% of users to shift their travel patterns to cross the bridges during the discounted, non-peak hours of the day.

A full understanding of demand-side strategies must recognize the reasonable limits of these applications. Demand-side strategies should not be considered total solutions to regional traffic congestion problems. Rather, they should more often be implemented as part of an integrated set of solutions that balance supply-side infrastructure investments and demand-side strategies. Demand-side strategies can be relatively easy to implement in a shorter timeframe, within a more constrained budget, than capital improvements. As such, supply-side and demand-side approaches can prove complementary – with demand-side efforts taking on an asset management role by maximizing the performance and extending the life of existing roadways. Successful demand management programs often leverage the synergistic results of many demand-side strategies working together – essentially producing the cumulative results of a number of small percentage improvements.

Demand-side strategies are ultimately about choice and balance. Expanding the array of mode, route and departure-time choices available – supported by robust real-time traveler information, incentives, and other resources – allows each person to choose the options that work best for them regarding when they travel, the mode and route they use to get there, or whether they travel at all.

What’s Inside?
Mitigating Traffic Congestion outlines a framework for understanding the full scope of demand-side strategies, and provides a wealth of case studies, both brief and in-depth, that illustrate where and how these strategies are already underway. The document is organized around these primary five sections:

The Demand-Side Framework – The broad framework for understanding demand-side strategies, their impact on traveler choices, and the varied settings where they are applied.

Summary of Case Study Experience – A review of the case studies collected and key lessons learned from the case study exploration.

Conclusions & Future Developments – A summary of concluding thoughts from the publication as a whole and highlights of important future developments.

Additional Resources & References – A collection of organizations, publications and internet resources, along with citations from this publication.

The Case Studies – In-depth case studies of over 25 examples of demand-side programs underway across the country.


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