While there are interactions among these factors, LPK is the only factor here reliant on the technical sophistication of vehicles themselves while FI and LPK are primarily a product of infrastructure and usage. 1.1 Vehicle Evolution During its development over the past century the passenger car has evolved from a rudimentary, self-propelled ”horseless carriage” to a sophisticated device capable of traveling hundreds of miles at high speeds. All new vehicles sold in the United States incorporate seat belts and at least two airbags; virtually all new vehicles include air conditioning and automatic transmissions to increase driver comfort and many also include navigation systems, moonroofs, and a bevy of other electronic aids. Gains in performance, size and fuel economy are relatively straightforward to analyze, as these factors have been carefully tracked since 1975 in the EPA Fuel Economy trends report. As shown in Figure 1-1 below fuel economy grew rapidly from approximately 1977-1987 and has since remained relatively constant. Vehicle performance has continually increased since the mid-1980s and vehicle size, measured using interior volume, has also grown modestly over the same time period. However, vehicle capability has improved in other ways as well. Vehicles are safer, emit fewer criteria pollutants per mile traveled, and include a broad array of equipment designed to improve dynamic capabilities provide the driver with a high level of comfort and information. [Cheah, 2010] highlights the importance of vehicle features by comparing two ve- hicles: a 2008 Audi A4 and a 2006 Mazda3 Touring, as shown in Table 1.2. The two vehicles are nearly identical in performance, interior space, exterior dimensions and highway fuel economy. However, the Audi has a significantly longer list of standard equipment, performs better in several crash tests, is 50% more expensive and weighs 345 kg more than the Mazda. Cheah attributes the mass increase primarily to the higher feature content of the Audi. However, this is only a single data point: a closer examination is needed to address the fleet-wide impact of features on the mass of 17
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