In the past, the heavy duty truckers have been able to purchase sealed beam headlamps for the trucks using either a 2 round system or the 4 round system, with longer design life low beam filaments.
In the '80's, many of the new truck models use rectangular sealed beams, however, these sealed beams were only available in the standard automobile life design. Truck operators noted the increase in replacement frequency and the additional costs related to the rectangular sealed beams.
This paper covers the research, development and testing of the long life halogen sealed beam headlamps in the last several years. The final results of field testing are not yet completed, as only two filament failures have been reported after 19 months of use on heavy duty trucks.*