For the three cities under study, key similarities and differences
were found in the dataset on the monthly average
number of congested hours per day from April 2004 through
April 2007:
Weekday congestion (a.m. and p.m. combined):
• All three cities had low congestion in December
(between approximately ½ to 1 hour fewer congested
hours per day). The lowest level of congestion for
Chicago and Houston was in December, but in August
for Los Angeles.
• All three cities had higher than average levels of
congestion in both September and October. Chicago
and Houston had the highest levels of congestion in
September, while Los Angeles had its highest congestion
in March.