With just a pair of lanes in each direction -- and no shoulders -- it doesn't take much for the 4.7-mile flat section of the span between Hayward and Foster City to back up, especially during the westbound morning commute. Growth in traffic -- more than 81,000 vehicles a day now travel the bridge -- overwhelm the two lanes and the toll plaza. An accident or stall can bring traffic to a standstill.
https://www.sfgate.com/bayarea/article/Expanded-bridge-set-to-open-early-San-Mateo-2777417.php
https://en.wikipedia.org/wiki/San_Mateo%E2%80%93Hayward_Bridge#Widening_(2002%E2%80%932003)
https://en.wikipedia.org/wiki/Tacoma_Narrows_Bridge#Westbound_bridge 4+4 lanes
https://en.wikipedia.org/wiki/Ship_Canal_Bridge 8+4 lanes
https://www.youtube.com/watch?v=sSVBkMu4uIA
http://citylivingseattle.com/Content/News/Urban-Dwellings/Article/The-Ship-Canal-Bridge-The-driving-force-in-Seattle/22/169/89385
