At 5 p.m. every weekday, cars pour from Silicon Valley tech campuses onto northbound Interstate 880, many of them converging at one notorious chokepoint.
It starts near the pedestrian overcrossing that connects Eldridge and Peterson avenues in Hayward, a horseshoe of asphalt swooping over an extremely jammed freeway. In the gathering dusk, drivers swarm from the cloverleaf interchange at Tennyson Road, headed toward another spaghetti tangle where I-880 intersects with Highway 92.
Engineers at Caltrans have identified this stretch of freeway as the Bay Area’s No. 1 bottleneck — not in the technical sense of lanes merging, but in the more colloquial sense of traffic routinely slowing to a crawl. The agency has a bespoke definition of “bottleneck,” meaning a 20 mile-per-hour drop in speed that continues for several miles, or for five “contiguous” five-minute detection points…