Report from CBS News mentions the bridge handled "11.5 million" vehicles a day.
EDIT: That number seemed fishy; I think the reporter is referring to the traffic along the entire I-95 corridor.
EDIT: That number seemed fishy; I think the reporter is referring to the traffic along the entire I-95 corridor.
Per another comment it's much closer to correct for the annual number of vehicle crossings.
11.5 million cars/day is equivalent to :
~48,000 cars/hour
~8,000 cars/minute
~130 cars/second
11.5 million cars per year however works out to:
31,000 cars/day
1,300 cars/hour
21 cars/minute
Peak capacity for a highway lane is just shy 2,000 vehicles/hour:
<https://www.mikeontraffic.com/numbers-every-traffic-engineer...>
Which would put the Key Bridge's maximum capacity at about 192,000 vehicles/day.
For comparison, the San Francisco-Oakland Bay Bridge saw about 42.7 million paid toll crossings. As these are metered only in the westbound direction, actual crossings are likely double that, or 85.4 million/year, or about 230,000/day.
(The bridge sees 1/3 the total traffic of all California state-owned bridges.)
<https://mtc.ca.gov/operations/programs-projects/bridges/san-...>