for decades, often exceeding their original design life and traffic volumes. As a result, the system is deteriorating and heavily congested.
The scale of highway renewal needs is suggested by the available national data. Using 1999 obligations, the Transportation Research Board (TRB) (2001) found that resurfacing was being performed on 12.85 percent (20,586 miles) of the National Highway System (NHS) annually, yielding a 7- to 8-year resurfacing cycle for the 160,000-mile system. Reconstruction had been performed on 3,200 miles of roads, implying a 50-year replacement cycle and therefore a need for a 50-year roadway, in contrast to the typical design life of 20 years. Furthermore, the average age of bridges in the national inventory is 40 years; 27.5 percent of this inventory is structurally deficient or functionally obsolete (FHWA 2004).1
The available data on the impacts of congestion are staggering. In 2005, congestion cost travelers in 437 urban areas 4.2 billion hours and $78 billion and resulted in the waste of 2.9 billion gallons of fuel (TTI 2007, Exhibit B-11, p. B-19). Congestion is being experienced during more hours of the day and is becoming more volatile, increasing travel time unreliability. The additional fuel consumed and idling vehicles contribute to environmental damage. Congestion may make an individual late for work, miss an appointment, or wait a long time for a bus; indeed, it may determine a person’s entire weekday schedule. To the private sector, congestion means higher transportation and logistics costs, fewer deliveries or service calls per day, and wear and tear on employees and vehicle fleets. For truckers who provide just-in-time freight deliveries to manufacturers and other businesses under service-level agreements, the penalties for failing to deliver on time can amount to tens of thousands of dollars.
The magnitude of the infrastructure renewal and congestion problem increases significantly when one considers growth predictions for the next
These terms are defined as follows by the Federal Highway Administration (FHWA 2004): “Bridges are considered structurally deficient if significant load carrying elements are found to be in poor or worse condition due to deterioration and/or damage, or the adequacy of the waterway opening provided by the bridge is determined to be extremely insufficient to the point of causing intolerable traffic interruptions” (Chapter 15, at www.fhwa.dot.gov/policy/2004cpr/chap15c.htm#body). “Functional adequacy is assessed by comparing the existing geometric configurations to current standards and demands. Disparities between the actual and desired configurations are used to determine whether a bridge should be classified as functionally obsolete” (Chapter 3, at www.fhwa.dot.gov/policy/2004cpr/chap3c.htm#body).