M
ost traffic on streets and highways around the Bay Area — and around most of the rest of California, for that matter — vanished in a matter of days in early March as the coronavirus pandemic arrived here and health authorities imposed shelter-at-home orders.
But data on our travel habits bears out what we're seeing on traffic maps and on the streets around us: Slowly but surely, traffic is building again throughout the Bay Area.
Analysts have worked out a variety of ways to use location information captured by our mobile devices to watch travel patterns and assess the impact of the shelter orders.
One basic metric derived from the mobile data is the total number of vehicle miles traveled, or VMT, in communities across the country. San Francisco's StreetLight Data has partnered with another data firm, New York-based Cuebiq, and put together an interactive map tracking how VMT has changed during the pandemic compared to a January baseline.
The first chart below shows VMT for all nine Bay Area counties between Sunday, March 1, and Friday, May 15. Highlights:
- Traffic across the region in those first few days of March was at or above that recorded in January, which StreetLight is using as a baseline month.
- As businesses began adopting telecommuting, travel dropped precipitously in the second week of the month.
- Travel plummeted further on March 17 when shelter orders forced the closure of "non-essential" businesses.
- All nine counties recorded their lowest traffic days between April 8 and April 12. Travel has begun a slow rebound since then.
The chart below gives a snapshot of the extent to which Bay Area VMT has recovered since the April low point. The chart reports Friday traffic for five consecutive Fridays starting April 10. Highlights:
- Overall, traffic in the nine counties has surged 61% from its nadir.
- However, traffic in the nine counties is still 73% below its March 1 level.
- The counties with the highest percentage increases since April 10: Contra Costa (85), Santa Clara (75) and Napa (66).
- The counties with the lowest percentage increases since April 10: Sonoma (38), Alameda (43) and San Francisco (45).
And finally: A look at per capita driving numbers across the region. Solano County has consistently recorded by far the highest numbers. San Francisco and Marin have had the lowest numbers.