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19 Table 2.1. Percentage of Contribution to Total Delay in Urban and Nonurban Areas Large Urban Areas Small Urban Areas Cause of Delay >1 Million Population 0.11.0 Million Population Rural Recurring Causes Network Demand > Capacity 2937 2026 0 Poor Signal Timing 45 610 2 Total Recurring 3342 2636 2 Nonrecurring Causes Crashes 3536 1926 26 Breakdowns 67 610 25 Work Zones 819 2627 39 Weather 56 710 7 Special Events/Poor Information 1 <1 0 Total Nonrecurring 5569 5873 97 Source: Summarized in Lockwood, 2006. From FHWA table combining recurring congestion data (TTI) and nonrecurring congestion data (ORNL). The first four strategy applications to improve reliability duration of delays--over 50% reduction in one case--as a result are well understood, and best practices are visible in a several of incident management. locations. However, active traffic management--the most Table 2.2 illustrates the broad range of other strategy aggressive approach to avoiding disruption and managing applications and their impacts. Safety service patrols reduce when it happens--is in the early stages of development in incident clearance times and related accidents; up-to-date both the United States and Western Europe. traveler information systems provide improvements in trip reliability; ramp and lane operations management increases throughput; and work zone management minimizes dis- The Potential of SO&M ruption. Of special importance are the high benefitcost of Regarding NRC these strategy applications and the potential for networkwide As suggested in Figure 2.1 and Table 2.2, the best practice improvement, compared with the more focused and expen- examples provide convincing evidence that these strategy sive investments in capacity. applications can have significant impacts on otherwise deteri- orating service, while providing visible evidence of the agency's Systems Operations commitment to addressing the mobility challenges facing and Management its customers. Figure 2.1 illustrates a range of impacts on the The concept of SO&M has evolved since the 1991 Intermodal Surface Transportation Efficiency Act (ISTEA). SO&M refers 80 to the broad notion that transportation agencies can apply a Average Reduction in set of known strategy applications to maintain and improve Incident Duration (%) 60 highway service in the face of recurring peak-period conges- tion and nonrecurring events such as major crashes, weather, 40 and special event disruptions. There are several excellent best practice examples of SO&M applications on the part of state 20 DOTs in a few major metropolitan areas in the United States. They include highly integrated incident management, well- 0 managed work zone control, and innovative traveler infor- A an d A M TX mation programs. However, these examples obscure a more ,V yl G ,N io, x ar ta, e irfa M lan qu nto n general reality: at the statewide level (even in states with the Fa At er qu nA well-known examples), best practice is confined to one or two A lbu Sa congested metropolitan areas, and even in those areas, only a Source: FHWA, ITS Benefits and Costs Database. narrow range of strategy applications is applied. Therefore, Figure 2.1. Best practice incident there is significant opportunity for improving this generally management reduction. low level of implementation.