The steel industry has also been able to deliver changes when needed. The pressure to reduce fuel consumption through vehicle design has been the driving force behind the development of high-strength steel (HSS). The fuel shortage in the early 1970s sent some engineers scurrying to build smaller cars. Other engineers went to the lab, examining materials and manufacturing processes that would enable lighter cars without compromising size.

The properties of HSS allow thinner gauges to be applied throughout the vehicle body, rendering a stronger, lighter vehicle without significant changes in cost structure. As mentioned in an article in April AEI about the new UltraLight Steel Auto Body Advanced Vehicle Concepts (ULSAB-AVC) project, HSS is now up to five times stronger than mild steels, with 80% of today's steels being developed in the 1990s. Engineers working on the ULSAB-AVC define HSS as having an incoming yield strength of 210 to 550 MPa (30 to 80 ksi); anything greater is considered ultra HSS.

Like any other new material introduced into a process, HSS has unique characteristics that require special attention. For example, the appeal in applying HSS has much to do with its ability to carry a great deal of stress vs. other materials, and peak faster than other materials during high energy loading such as during a car crash. This property allows engineers to scale back on the mass applied for a particular body part, cutting mass out of the entire structure. That same property, however, has posed some unique challenges to the automotive industry. The lower ductility of HSS means greater care must be applied during the design and manufacturing stage.

Working with HSS can be a more detailed, sensitive process. Variances in the steel often throw off the balance of the process, resulting in less uniform parts. There is also the problem of the springback that occurs in HSS during the stamping process. While most grades of automotive steel exhibit springback to some degree, the magnitude of springback depends on the steel's yield strength and sheet thickness, making HSS particularly vulnerable. Engineers in the automotive industry are in the process of developing computer models to predict more accurately the behavior of HSS during the manufacturing process, but more experience is needed to pinpoint the accuracy of the models.

But the industry is gaining experience. According to a report published by American Metal Market in 1999, since 1977 automakers' use of HSS sheet grades has increased by 162%, while the use of all grades of aluminum (castings, extrusions, foil, sheet, etc.) has increased by 143%. The report also says that HSS sheet replaced older, carbon steel grades, whereas the growth of aluminum came largely in the form of castings, principally as a replacement of cast iron.

According to the 1999 report, vehicles included on average about 816 kg (1800 lb) of steel in the form of sheet, bar, and other types, which accounted for about 55% of the average vehicle mass, a proportion that has remained constant for more than a decade. About 680 kg (1500 lb) of that amount was sheet, of which 149 kg (328 lb) was HSS. The report says that the total amount of aluminum in a vehicle was 107 kg (236 lb) on average.