In early 1973, the continuous roadway lighting on the southbound main lanes of Interstate 35 through Austin, Texas, was turned off as a power-saving measure in response to a critical area energy shortage. Analyses of accident data revealed that this cutback in roadway lighting significantly increased the frequency, rate, and severity of nighttime accidents in the affected freeway sections. The most notable increases were associated with a sharp rise in nighttime rear-end and pedestrian-related accidents. The cutback in roadway lighting saved approximately 450 000 kW· h of electrical power per year, enough to maintain 20 all-electric homes of average size for the same time period. In terms of energy cost savings to the city, this reduction amounted to $25 250/year. In addition, estimated savings of $2500/year in lamp-replacement costs were realized through the cutback. However, increases in accident costs after the lighting cutback were conservatively estimated to be slightly less than $17 000/year. Therefore, although positive energy conservation gains were made through the lighting cutback, these gains were accompanied by a measurable decrease in motorist safety.

On January 3, 1973, the Texas State Department of Highways and Public Transportation (TSDHPT) granted the city of Austin permission to turn off the continuous roadway lighting on the southbound main lanes of Interstate 35 through the city. The city requested the lighting cutback in response to a critical shortage of electrical power in the area. After the department's authorization was received, the lighting cutoff was carried out by city technicians between January 9 and 15, 1973. The lighting reduction affected only the main lanes in three freeway sections that had a total length of 7. 2 miles. Section 1 had median-mounted lighting and all lighting for the southbound lanes was turned off. Sections 2 and 3 had shouldermounted lighting on both northbound and southbound lanes and, again, all lighting for the southbound lanes was turned off. Ramp and frontage road lighting in the three sections was not affected by the cutback.