Used by an auto magazine to speed-test cars in the 1970s and 1980s, how long was Bonnie Orcutt's driveway?

Great question! Her "driveway" was 4.1 miles long. She petitioned everyone, including Ladybird Johnson, to have the road built to give her access to the highway and the county finally complied. The road cost $100,000 in 1960s money and Mrs. Bonnie Orcutt was the only resident on it.

The road testing that "Car and Driver" did on the road was illegal and dangerous, however, Mrs. Orcutt never complained. In fact, she seemed to enjoy the attention.

https://www.caranddriver.com/features/a15385694/mrs-orcutts-driveway-204-mph-on-a-double-nickel-road-page-1/