Summary Bottom Line Report  |  Full Bottom Line Report

 

Determining Highway Investment Requirements

The Current Context

The analysis of future vehicle miles of travel and other dynamics which will determine highway and transit needs takes into account many rapidly evolving factors:

  • It incorporates research used by the National Surface Transportation Policy and Revenue Study Commission, “Transportation for Tomorrow,” 2008, to develop forecasts of VMT.

  • Recent trends in vehicle miles of travel, transit ridership, per capita incomes, and fuel prices have been used to shape the forecasts for the next six years of authorization and for the 20 years of highway and transit investment needs.

  • Ten-year trends in the growth of vehicle miles of travel for the United States through 2007 were at 1.6 percent per year, and six-year growth of VMT has been an average of 1.2 percent per year. VMT has declined from 3 trillion in 2006 to 2.9 trillion in late 2008.

  • Ten-year growth trends in transit ridership have been at 2.4 percent average per year, which is well above the base case numbers used for all recent transit needs analyses.

  • Clearly, previous forecasts need to be adjusted to reflect the factors that are driving VMT growth and transit passenger growth. At the same time, the declining VMT trend seen over the past two years is not expected to continue for the next 20 years.

 

Past Forecasts of Vehicle Miles of Travel

Between 1993 and 2004, highway vehicle miles of travel (VMT) grew at an annual rate of 2.3 percent. This was slower than the rates for the two previous decades. The 20-year forecasts made by U.S. DOT in 2004 called for future growth rates of 2.02 percent. By the time of their 2006 report, they had reduced their forecast to 1.91 percent. More recent trendlines have pointed to an even slower future rate of VMT growth.

The forecast sources utilized for the previous Bottom Line Reports and the U.S. DOT’s Condition and Performance reports have been the annual Highway Performance Monitoring System (HPMS) data sets submitted by the states to the FHWA. The HPMS data submitted by the states includes information on a sample of highway segments in each state.

A projection of 1.4 percent growth in VMT is the base case for highway VMT growth used here.3 In addition to this base case, needs analyses have also been conducted for a future VMT growth rate of 1.0 percent per year (effectively constant VMT/per capita with population growth at about 1 percent. AASHTO studies have shown that holding the rate of growth in VMT to under 1 percent annually will help reduce greenhouse gas emissions, a part of the transportation sector’s strategy to be helpful regarding global climate change). A forecast of 1.91 percent growth, which is the HPMS forecast, was also analyzed. In addition, a no growth forecast, holding VMT at present levels has been developed to help understand the nature of underlying needs in the backlog.

Why is the rate of travel growth declining? There are several factors which together explain this trend. The population growth rate in the United States has slowed from 1.3 percent in 2001 to around .95 percent in 2007. The worker boom of the 1970s and 1980s has ended. The boom came about due to the large number of baby boomers who entered the work force in this period and the increasing participation of women in the labor force. Although the overall population is expected to grow 20 percent between 2000 and 2020, the age group of new drivers licensing, 15 to 19, will only grow about 6 percent. The percentage of the population of the age 65 and higher will grow significantly. People of the age 65 and above tend to travel less than younger age groups. Vehicle ownership is at near-saturation levels: today one-third of households have one vehicle, 40 percent have two, 17 percent have three, and only 10 percent have none. The next two factors are expected to be temporary in nature: First, the United States experienced record high gas prices from 2006 to 2008 of $3 to $4 per gallon, up from under $2 per gallon in 2000 to 2005. Prices have just dropped to under $2 again. Should prices increase again, as is expected, this will tend to dampen the rate of travel growth. Second, today the United States economy is undergoing one of the most serious economic downturns in decades. Highway travel has declined as a result. Once the economy recovers, the rate of growth in VMT is expected to resume to somewhere in the range of 1 percent to 1.4 percent per year.

 

Current Highway Conditions and Performance

There are over 4 million miles of roads in America connecting our vast land area. In 1950, when our nation had 150 million people, our road system was 3.3 million miles. Since then, the population has doubled and the road system has grown by about 20 percent. In 1950, there were just below 50 million motor vehicles, today the national fleet is about five times that number. Those vehicles traveled about 500 billion miles per year in 1950 and now are at 6 times that level at approximately 3 trillion miles. That mileage is owned by different levels of government and divided into functional classes that do different levels of work in the national system.

 

 

 

Condition and Performance

Pavement Condition and Ride Quality

U.S. DOT’s Condition and Performance Report of 2006 indicates that there have been mixed trends in pavement condition, with improvement seen primarily in rural areas and decline or status quo in urban areas large and small.

Between 1995 and 2004, the share of travel on pavement in “Acceptable” condition in rural areas rose from 91.5 percent to 94.5 percent; while travel in urbanized areas declined from 83.5 percent on “Acceptable” pavement to 79.2 percent. Travel in small urban areas remained without change at about 84 percent on “Acceptable” pavement throughout the period.

Interstate pavements do best in the ratings; sustaining ratings approaching 98 percent of all travel on rural Interstates on pavements of “Acceptable” quality. Urbanized area interstates are rated lower in quality but still are quite effective, with 90 percent of travel on “Acceptable” pavements. When the percentage of travel rated “Good” is considered, the contrast between the condition of urban and rural systems is more clear, with almost 74 percent of rural travel on “Good” pavements, contrasted to only 48.5 percent of urbanized-area interstates. Other urbanized area freeways and expressways fare worse at 37.8 percent of travel on “Good” pavements, and their principal arterials are worse yet, with less than 25 percent of travel on “Good” pavements.

System Performance

The performance table below shows the across-the-board declines in every measure of travel performance at all metro levels of population size over the past 18 years. It also shows that the smaller metropolitan areas are rapidly closing the gap with larger areas regarding levels of congestion. The greatest increases in congestion occurred in the smaller metropolitan areas.

 

Bridge Conditions and Backlog

The public travels over the almost 600,000 bridges in the nation on the order of a billion times each day, often without noticing. State highway agencies own, maintain, and manage the largest share of American bridges, with 277,000 of the total. County highway agencies manage the second greatest share—230,550 bridges.

If a concept called deck area, which encompasses bridge length and width, is used, providing a sense of scale of bridge size, then state highway agencies own more than 70 percent of bridge area. There are 116,000 bridges on the National Highway System, which accounts for 4 percent of the nation’s roads but about 45 percent of its travel. These are the nation’s main bridges and almost all of them, 95 percent, are owned by the states.

One great concern about our bridges is their age. The figure (bridges by age) shows the age for the bridges built over the past 100 years or more. Roughly half of our bridges are more than 40 years old.

 

Bridge Condition Concepts

Bridges are evaluated based on their ability structurally and functionally to meet the demands placed on them.

Structurally Deficient—A bridge that cannot meet the load-carrying capacity needs or other condition aspects will be considered structurally deficient. All such bridges do not need to be closed. They often can continue to function with rehabilitation or load limits placed on them.

Functionally Obsolete—A bridge that is not consistent in design with the related highway systems in terms of lanes, widths, curvature etc. is deemed functionally obsolete and in need of an upgrade. Generally these bridges are too narrow for modern trucks.

The figure (year built and percent deficiency) shows the percentage of bridge deficiencies by year built. The figure sharply illustrates that, although only half of our bridges are more than 40 years old, they account for more than 80 percent of structural deficiencies and about 75 percent of total deficiencies.

 

Improvement in Bridge Deficiencies

The record shows strong improvement in addressing structural deficiencies on our nation’s bridges. In 1994, more than 107,000 bridges, almost 19 percent of the nation’s bridges, were structurally deficient. This dropped sharply to under 74,000 by 2006, and to below 73,000 in 2007. Such bridges are now below the number of functionally obsolete bridges.

The trend for functional obsolescence has slowly improved from about 14 percent of bridges in that category in the 1990s to 13 percent in this decade.

 

Conditions and Performance Measures in the Bottom Line

In order to establish the base for analysis in 2009, highway conditions for 25 years were projected using the FHWA Highway Economic Requirements System (HERS) model and then modified by applying actual spending in recent years and estimates for the years for which data do not yet exist. Performance measures are generated by the HERS model that describe the outcomes of different investment levels. This document focuses on five performance measures:

  • Pavement Condition—The International Roughness Index (IRI), is used to provide a sense of the level of pavement service.

  • Delay Experienced by the Public—The primary measure used is hours of delay per 1,000 miles of vehicle travel based on the concept that no additional amount of time should be needed to produce a given level of travel in the future. Total delay is the sum of signalization effects, delay due to incidents, and congestion-based delay.

  • Speed of Travel—Vehicle speed is used as the most straightforward measure of system performance quality.

  • Percent of VMT on Congested Roadways—This measure assesses the scope of overall traffic congestion in establishing how much of travel services is under negative conditions.

  • Total User Cost—User cost components sum up vehicle operating costs (trucks and personal vehicles), crash costs, and travel time costs.

 

Next Page >>