From the Washington Post via Dick Pratt, an Obituary for Walter Hansen, developer of the Hansen accessibility measure.
Walter George Hansen - Transportation Consultant
"Walter George Hansen, 76, founder of a transportation planning consulting company, died of cancer May 15 at Inova Fairfax Hospital. He lived in Annandale.
"Mr. Hansen co-founded Alan M. Voorhees and Associates in 1961. By the mid-1960s, it was operating worldwide. It was acquired by Planning Research, later Ashland Technology and finally AECOM Technology. He worked for each of those firms in executive positions, including chief operating officer. He retired in 1996."