MEASUREMENT OF HEADLAMP AIM AND THE ELECTRICAL AND PHOTOMETRIC PERFORMANCE CHARACTERISTICS OF REAR LIGHTING SYSTEMS

The purpose of this study was to collect and analyze field data pertaining to (a) headlamp aim and (b) rear lighting system electrical performance of a sample of vehicles representative of current makes/models. Using mechanical aimers, headlamp aim data were collected from 768 vehicles; half from a periodic motor vehicle inspection (PMVI) state (Virginia) and half from a non-PMVI state (Maryland). Results showed that about 55% of Virginia vehicles had both headlamps aimed within the Society of Automotive Engineers (SAE) standard compared with about 43% for Maryland vehicles. About 69% of newer vehicles (1991 models) had both headlamps aimed within the SAE standard as compared with about 35% for older vehicles (1986 models). There was no significant relationship found between headlamp aim and the number of months since inspection, fuel level, load, or headlamp type. Rear lighting system voltage and amperage data were collected from 200 current model vehicles (1986-1991 models). Some newer vehicles (1991 models) had significantly higher voltage readings than some older model vehicles (1988 models) at the rear lighting system. Cars had significantly lower voltage readings at the rear lighting system than vans, light trucks, and utility vehicles.