Premium private transit
Historically, workers have lived in suburban locations and commuted to the city for work, but Silicon Valley sees the reverse. Many knowledge workers tend to be young, educated, and in search of an urban lifestyle; they prefer to reside in the city and commute to the suburbs where the large technology companies are based. While the employees used to organize unofficial carpools and vanpools, now the tech companies manage full-fledged fleets to transport their workers over 30 miles to the job sites. The companies with the most active shuttle routes include Google, Apple, Facebook, Electronic Arts, Yahoo and eBay; the companies don't release ridership or frequency data, but according to a project by Stamen Design, these shuttles transport roughly 35% of the number of passengers that Caltrans moves each day .
The buses tend to be fairly nondescript, and are described as comfortable and quiet inside. They all have wireless internet, which allows employees to start working during the commute 
Traffic and Environmental Impacts
The San Francisco County Transportation Authority estimated that the private shuttles save a net 28.7 million VMT and replace roughly 757,000 single-passenger car trips. 
- Google operates a fleet of about 95 private buses serving 35 routes in seven counties, and they recently incorporated double decker buses into their fleet.  The company's transportation program includes biodiesel engines and solar-powered charging stations.
- Between 40 to 47% of Facebook's employees use alternative transportation, which includes their six shuttle routes.
- Apple estimates that its various shuttle, transit subsidy and carpool programs have taken the equivalent of 4,500 cars off the road, according to its 2008 Environmental Update. 
Relations with San Francisco Muni have been tense, as the large private shuttles occupy more than 200 boarding sites across the city.  Although transit officials acknowledge the private shuttles help take cars off the road, they are pushing for more regulation. The shuttles often pick up workers at Muni bus stops, which creates delays for public transit riders, and neighborhood residents complain about the large buses on their streets. SFMTA is beginning to address the issue, by dedicating new loading zones away from existing transit stops and proposing a fee on the companies that use them. Additionally, some criticize the shuttles for competing directly with public transit. However, neither the employers and employees live close to the Caltrain commuter line, and passengers are unwilling to make several transfers and to wait for the train's infrequent service. 
Many view the private transportation system negatively, accusing it of contributing to gentrification. Real estate seems to have been affected, with even low value homes selling at a premium because of their proximity to a private shuttle stop 
Integrating Private Shuttles into the Transportation System
SFCTA Strategic Analysis Report
San Francisco has seen significant growth in shuttle operations, most of which are private, employer-operated buses. SFCTA issued a report that analyzed the role of private shuttles in the transportation system. Although the buses are legal under the CPUC, field work noted that private shuttle can come into conflict with Muni operations or they violate restricted parking areas. Surveys with community members and shuttle passengers identified areas of concern, such as the vehicles' large sizes, localized pollution and noise, and vehicle anonymity (making it difficult to report complaints). However, the report also notes that shuttle operations have positive impacts, many of which are complementary to transit. Private shuttles not only help reduce VMT and car ownership, they can also improve employees' productivity and quality of life.
The key findings of the benefits/impacts analysis were:
- Significant regional benefits, but with localized impacts, such as improper use of curbs and idling.
- There is evidence that motor coach vehicle size and weighting are not ideal for some streets.
- The public would benefit from a point-of-contact for inquires, feedback, and complaints.
- The extent of issues and growth of shuttles indicates long-term need for shuttle planning, coordination, and management.
Other cities are also working on ways to allocate scarce curb space. Possible policy solutions can be to implement shared bus stops, create dedicated shuttle zones, and sharing bus parking facilities. Additionally, employers in South of Market have begun to explore consolidation of their shuttle services to reduce costs and redundancy, but there are barriers due to the complexity of negotiating service parameters, cost-sharing, new entrants, and governance among several firms. However, there currently are several models in the Bay Area where multiple shuttle providers coordinated resources to provide a circulator shuttle service.
Finally, the report made several recommendations for better integrating shuttle operations with the existing transportation system:
- Create a "Muni Partners" program, which would formalize and streamline coordination between the shuttle industry and SFMTA. The authors recommend a fee structure for members of the program in order to cover curb management and facilities fees.
- Set clear policy objectives to ensure safety and complementary interactions with transit and other road users
- Work with potential new entrants to the shuttle market to foster development of support for broader transportation sector goals, e.g. congestion management
- Create needed facilities to accommodate existing shuttle operations
- The City from the Valley
- The Commuter Kings: Riding Along on Silicon Valley's Exclusive Shuttles
- Google and other high-tech companies packing in riders.
- Employee Shuttles Finding Their Place in SF's Complex Transit System
- New loading zone proposed
- The Silicon Valley Shuttles Revealed.
- Are Silicon Valley's Employee Shuttles Bad for San Francisco?
San Francisco County Transportation Authority. "Strategic Analysis Report: The Role of Shuttle Services in San Francisco's Transportation System". (2011).
- The San Francisco County Transportation Authority released a report which analyzed the impacts of private shuttles in the transportation network.
California Center for Innovative Transportation. “Privately-Provided Commuter Bus Services”. (2010).
- The CCIT report also analyzed the impacts of regional shuttles in San Francisco.
Stamen Design. "The City from the Valley"'. (2012).
- Stamen Design created a map of the shuttle buses; their process of tracking the buses is outlined here.