Our Northwest

Tight squeeze on I-90 bridge should be safe

Thursday, June 1, 2017by  Jon Osterberg

Traffic crowds the I-90 Lake Washington Floating Bridge in SeattleInterstate 90 floating bridge commuters lose their express lanes for good this weekend, and by reconfiguring the roadway to accommodate light rail, they also face a tighter pinch.

How tight? Since 1993, I-90 bridge travelers have enjoyed roomy lanes 12 feet wide. The reconfigured bridge surface offers lanes that vary from 11 feet wide at Lake Washington's shoreline to as little as 10.5 feet on the floating spans.

The narrower lanes enable the addition of high-occupancy vehicle (HOV) lanes that run in each direction, replacing the express lanes soon to be annexed by light rail.

Cars squeeze across the Aurora Bridge in SeattleThe good news is, even at 10.5 feet wide – which also is the width of the lanes in the Mount Baker Tunnel, according to WSDOT spokesperson Annie Johnson – it will feel spacious compared with gauntlets like the Aurora Bridge, which has lanes just 9.5 feet wide, or some lanes of the Alaskan Way Viaduct that also are 9.5 feet.

For further comparison, consider I-5 through downtown Seattle. Johnson told me those lanes are 11 feet wide. The new Alaska Way replacement tunnel bored by Bertha also will have 11-foot lanes.

A typical car is about six feet wide, giving drivers on the reconfigured floating bridge more than two feet of wiggle room on each side. Metro buses are 8.5 feet wide, so passing them – or 18-wheelers – might make drivers feel a little pinched.

Traffic crowds the Alaskan Way Viaduct on Seattle's waterfrontBut as for safety concerns, a transportation expert at the University of Washington told The Seattle Times in 2001, "If 11-foot lanes cause people to pay more attention while driving, they will be safe or safer than the existing 12-foot lanes."

Cross-lake commuters should expect backups and longer drive times for a while.

"We expect some congestion because that always happens as drivers get used to road changes," Johnson said. "But people are adaptable, and it should improve pretty soon."

True. After crossing the Evergreen Point Floating Bridge each weekday during the five years of SR 520 reconstruction, I saw motorists adapt fairly quickly each time they weaved atop new detours and interim asphalt between the lake and I-405.

The original span of the I-90 Lake Washington Floating Bridge sank in a November 1990 windstormFor further peace of mind, older drivers will recall crossing the I-90 bridge after the original span sank in a November 1990 storm. Until the sunken span was replaced in 1993, traffic in both directions crowded onto the north span (today's westbound lanes) that had opened in 1989. During that time, those lanes were 11 feet wide.

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