Terwilliger curves

The "Terwilliger curves" is the name given to a 1.7-mile (2.7 km), six-lane section of Interstate 5 (I-5) in Portland, Oregon, known as one of the most dangerous stretches of highway in the state. Named for its physical characteristics and proximity to Terwilliger Boulevard, it first opened in 1961 and soon became known for its high accident rate. Several upgrades, a reduction in the speed limit, and increased efforts to enforce traffic laws have had some success improving safety over the years, although accidents remain common.

The Terwilliger curves comprise less than two miles (3.2 km) of I-5 between the Willamette River and bluffs of Southwest Portland. The area is described in most media accounts as covering 1.7 miles (2.7 km) from 26th Avenue to Iowa Street, although some sources place it between Spring Garden and Iowa streets. In 2005, an average of 132,603 drivers passed through the curves each day.

The road's curve changes "five times in just over a mile [1.6 km]", and conditions are further complicated by speeding drivers, high centers of gravity in modern vehicles (particularly SUVs), "poorly banked curves" and occasional accumulated precipitation. According to Oregon Department of Transportation (ODOT) engineering manager Walt Bartel, the curves are the "only stretch of I-5 where you can't see far enough ahead to safely drive faster than 55 [mph (90 km/h)]".

The Terwilliger curves are "notorious" for being one of the "most accident-prone stretches" of I-5 in Oregon, and a "flash point for crashes, congestion and commuter frustration". ODOT traffic safety data from 1991 to 1993 found the Terwilliger curves had 272 accidents for 1.15 accidents per 1 million vehicle miles traveled (0.71 accidents per 1 million km). A later study showed there were an average of 100 crashes per year between 1995 and 2005. The phrase "Terwilliger curves" appears to have been first used by The Oregonian in a January 1988 report noting three car accidents on a foggy Sunday. The term has since been adopted to name a thoroughbred race horse and an indie rock band.

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Wikipedia