Route 237 begins at a junction of Grant Road with El Camino Real in Mountain View, as a four lane divided highway. Most traffic comes from California State Route 85. Westbound traffic can connect to Route 85 southbound, but the eastbound traffic connection to Route 85 northbound is labeled as an exit for U.S. 101. Route 237 intersects with Highway 101 at the southern corner of Moffett Field. After this intersection, a carpool lane is added, for a total of three lanes in either direction. It remains like this until the east end of the freeway at Interstate 880, where most eastbound traffic is directed to northbound I-880. The route then becomes a city street, Calaveras Boulevard, in Milpitas, terminating at Interstate 680. Exit signs from U.S. 101 north to Route 237 west currently say "Mountain View-Alviso Road". Starting from half a mile after the highway's western terminus, and ending at the I-880 intersection, Route 237 is mostly constructed to Interstate standards, and is named the Southbay Freeway. It is not part of the Interstate system, however. Route 237 is known for a number of companies that define Silicon Valley's technological landscape. Many major software and hardware manufacturers have their headquarters along 237. Some of these manufacturers include Lockheed-Martin, Brocade Communications Systems, Nortel Networks, Cisco Systems, Yahoo!, Juniper Networks, TiVo, Ariba and NetApp. SR 237 is part of the California Freeway and Expressway System, and is part of the National Highway System, a network of highways that are considered essential to the country's economy, defense, and mobility by the Federal Highway Administration.
Highway 237 Bikeway
The Highway 237 Bikeway is a pedestrian and bicycle path that parallels State Route 237. The majority of the path is separated from vehicular traffic, however, two sections comprising a total of follow an on-street alignment adjacent the freeway. This bikeway serves as an important connector in the network of trails in San Jose and Santa Clara County. It intersects with the Guadalupe River Trail, which provides access to Downtown San Jose, as well as the San Tomas Aquino Creek and Coyote Creek trails.
Express lanes
The SR 237 Express Lanes, the high-occupancy toll lanes along Route 237 in both directions between Mathilda Ave in Sunnyvale and I-880 in Milpitas, opened on March 20, 2012 east of North First Street and on November 22, 2019 up to Mathilda Ave. Instead of terminating exactly at the I-880 interchange, the Express Lanes continue along an connector ramp to I-880, so that eastbound Express Lane users merge directly into the I-880 northbound HOV lane, and I-880 southbound HOV lane users can directly enter Route 237's westbound Express Lane. Solo drivers are required to pay a toll via a FasTrak transponder. Later on, express lanes will be added on I-880, SR 85 and US 101.
History
Before Route 237 was upgraded to freeway status in the 1994-1995, it was a four-lane expressway with at-grade intersections, known as Alviso-Milpitas Road or Milpitas-Alviso Road depending on different maps showing the description. The Route 237 corridor has long been sought as a location for a freeway connector between Interstates 680 and 880. Many possible sites have been suggested, from Montague Expressway in North San Jose to Mission Boulevard in Fremont. One map printed before Route 237's construction to freeway standards between Alviso and 880 showed a new freeway across bay wetlands between Alviso and the Scott Creek Road interchange in South Fremont. Grading and underpasses for a freeway interchange are presently visible along 680 near Scott Creek Road.
