During peak traffic hours, there are in average about thirty or so significant incidents impacting traffic
at the exact same time on the Bay Area's major highways:
accidents, obstructions, road work ...
Frequently, there can be many more incidents affecting traffic at the same time.
On the radio, traffic updates are given at best every 10 minutes or so;
more likely, and depending upon the station, every twenty minutes.
Traffic is a significant concern for listeners; it focuses their attention. Radio stations leverage
this interest, earning income from sponsorship.
Consequently, in addition to broadcasting incidents, the announcers must acknowledge a list, often extended, of sponsors.
All in all, for each traffic update, there is time for announcing just
a handful of incidents.
For a particular update, broadcasters typically choose to focus on one particular area, such
as bridges. They then circulate through various areas in subsequent broadcasts.
They may focus on bridges again one hour later.
Thus, during the time that you travel on one particular highway
section, the odds are rather small that an incident affecting you will be reported in due time.
Lastly, broadcasters rarely report on anything else than
major highways, while SF Bay Traffic reports on about 10,000 different road intersections through the entire Bay Area.