Hourly
volumes and average speed on I-5
The
top panel below shows total hourly volumes (in numbers of vehicles)
on I-5 through the Golden Triangle area (north of La Jolla Village
Drive) for a typical one week period (January 23-29, 2005). Blue
curves are for northbound traffic; red curves are southbound. These
data very clearly show the difference between Saturdays (far right
hump), Sundays (far left hump), and weekdays (middle five humps).
The weekday traffic shows prominent peaks for northbound morning
traffic and southbound afternoon traffic, due to commuter patterns.
Northbound and southbound trips are almost balanced at all times
on weekends. The total northbound and southbound volumes (= the
area under each curve) are approximately equal. That is, averaged
over an entire day, there are just about as many northbound vehicles
as southbound vehicles at this location. Surprisingly the situation
is different for Interstate 805.
The
bottom panel shows average speeds (in miles per hour) as a function
of time of day, for the same one week period. Once again, blue is
northbound and red is southbound. We see here that the average speeds
can collapse down to as low as 10 mph (bumper-to-bumper traffic
jams) during peak hours. The PM southbound flow is more susceptible
to daily jamming than is the AM northbound flow.
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