Common use of RESEARCH BACKGROUND Clause in Contracts

RESEARCH BACKGROUND. Traffic speed is one of the most important variables for traffic operations and control. It is both a potential sign of problems on the roadway and a good measure of system effectiveness. Many incident detection algorithms are based on traffic speed data. Speed variation is also a good indicator of traffic safety (▇▇▇▇▇▇▇▇ and ▇▇▇▇▇▇▇, 2000). If good network-wide speed information is available, the travel time for any origin- destination pair can be calculated. Data concerning trucks and heavy vehicles are important for several reasons. Because of their heavy weight and large turning radii, long vehicles (LVs) have very different moving characteristics than short vehicles (SVs), which are mostly passenger cars. This affects a roadway’s geometric design factors, such as horizontal alignment and curb heights. The heavy weight of such vehicles is also an important factor in pavement design and maintenance, as truck volumes influence both pavement life and design parameters (AASHTO, 2004). Roadway performance is influenced by the presence of large and/or low-performance vehicles in the traffic stream because they reduce roadway capacity (▇▇▇▇▇▇▇ and ▇▇▇▇▇▇, 1983). The Highway Capacity Manual (TRB, 2000) explicitly stipulates that passenger-car equivalents of LVs under different conditions should be used for highway design. Safety is also influenced by LVs. A recent study found that 8 percent of fatal vehicle-to-vehicle crashes involved large trucks, although only 3 percent of all registered vehicles were large trucks (NHTSA, 2004). Recent studies (▇▇▇▇▇▇ et al., 2004; ▇▇▇ et al., 2004) also found that particulate matter (PM) is strongly associated with the onset of myocardial infarction and respiratory symptoms. Heavy duty trucks that use diesel engines are major sources of PM, accounting for 72 percent of traffic-emitted PM (EPA, 2001). All these facts illustrate that good speed and truck volume data are extremely important for accurate analysis of traffic safety, traffic pollution, and flow characteristics in transportation planning, management, and engineering. They are also important inputs for advanced traffic management systems (ATMS) and advanced traveler information systems (ATIS). Additionally, truck volume data are needed by federal and state transportation organizations to adequately monitor and analyze our nation’s freight movements. The Washington State Department of Transportation’s (WSDOT’s) dual-loop detection system classifies vehicles into four bins according to their lengths. The four length categories are described in Table 1-1. Because of variations in the lengths of vehicles within specific FHWA vehicle classes, the four WSDOT length classes do not directly relate to the 13 FHWA vehicle classes (▇▇▇▇▇▇▇▇▇▇, 1993). Typically, vehicles 40 ft and longer are referred to as LVs (▇▇▇▇ and ▇▇▇▇▇, 2003; ▇▇▇▇ et al., 2003), and those shorter than 40 ft are referred to as short vehicles (SVs). The majority of LVs on Seattle area freeways are trucks. Hence LVs and trucks are used interchangeably in this report. Class Length Range (feet) Vehicle types Bin 1 Less than 26 Cars, pickups, and short single-unit trucks Bin 2 From 26 to 39 Cars and trucks pulling trailers, long single-unit trucks Bin 3 From 40 to 65 Combination trucks Bin 4 Longer than 65 Multi-trailer trucks