In a city known for road diets and traffic calming, about 40,000 motorists a day can legally go faster when speed-limit signs on the Spokane Street Viaduct are changed this weekend from 35 mph to 40 mph.
The limit on the new road deck has been 35 mph since it was finished a year ago. The $164 million project widened the lanes to 11 feet, added merge and exit lanes, improved earthquake resistance, and removed a dangerous offramp from the westbound roadway to northbound Fourth Avenue South, replacing that with a First Avenue South ramp. However, the Seattle Department of Transportation (SDOT) made the initial speed the same as for the old structure, to see how traffic would behave.
Traffic engineers now believe that a 40-mph limit is safe. A speed sample of Wednesdays in November found the average car going 40.38 mph, dropping to 37 mph during rush-hour congestion, and averaging 43 mph late at night.
Some drivers travel closer to 50 mph, hindering the slower traffic trying to merge at First Avenue South or exit at Harbor Island. Farther west on the high West Seattle Bridge, the posted speed is 45 mph.
In related news, the SDOT says it has replaced worn-out overhead signs with new signs that are so reflective there’s no need to install electric lights on them — a trend that might help the city save money on future sign projects, according to spokeswoman Marybeth Turner.