Evaluating Alternative Operations Strategies to Improve Travel Time ...

SHRP 2 L11: Final Report
4. TRENDS AFFECTING TRAVEL-TIME RELIABILITY
This chapter provides an overview of the trends that are anticipated to shape future roadway travel
conditions, congestion, and reliability. Particular attention was paid to research documents and
other literature related to these topics:
1. Demographics, Land Use, and Urbanization
2. Environment and Climate Change
3. Energy Costs and Availability
4. Technological Innovation
5. Freight
6. Finance, Road Pricing, and Privatization
The following sections provide a summary of the research related to future trends that will likely
affect system reliability, the demand for roadway travel, and our ability to manage reliability.
DEMOGRAPHICS, LAND USE, AND URBANIZATION
According to the Census Bureau, the U.S. population will increase to 438 million by 2050—more
than a 40% increase from the 2008 population of 304 million. This will require more housing,
employment, and services, which may lead to large impacts on travel patterns and demands. The
U.S. will receive the largest population increase of any country in the world, primarily due to
immigration. As the Baby Boomers continue to enter retirement, the U.S. faces one of the mostdramatic
demographic shifts in its history. The baby boom ran from 1946 to 1960, during which
time the fertility rate in the United States was nearly twice its 20th century average. Because a high
proportion of the current population was born in that period, their age has a strong influence on the
average of the population. Thus the U.S. is, on average, growing older because of the baby
boomers as shown in Figure 4.1.
Figure 4.1 US Demographic Changes
Source: US Census Bureau
TRENDS AFFECTING TRAVEL-TIME RELIABILITY Page 37