Last night, Facebook disclosed that their car commute trips had spiked in recent months, adding about 400 more cars to San Francisco streets, due to new San Francisco rules changing shuttle stops.

Reviewing the the next expansion of their Menlo Park campus, Facebook shared results of their successful transportation program, which had about 50% of employees refraining from driving alone – until SFMTA changed shuttle stops as a result of resident protests. The drivealone rate, which had been about 50%, increased to 54% of Facebook’s 10,000 workers.

Napkin math suggests about 400 additional Facebook drivers on San Francisco streets and highway 101 following the shuttle changes. Facebook’s driving rate is still much lower than the 80%+ drivealone rate at typical suburban office parks.  But the extra cars are surely not what San Francisco’s policymakers and activists were hoping for.

If other employers such as Google, Apple, and Genentech are experiencing similar shuttle dropoff, San Francisco may be seeing over 2500 additional cars per day on city streets due to the changes in the shuttle program. SFMTA’s plans call to study further consolidating shuttle stops into a hub model, which could further depress shuttle ridership.