Civil Engineering Reference
In-Depth Information
60 mph) used as the basis in measuring the Travel Time Index. In practice each
10.4.2 Not All Travelers are Impacted by Traffic Congestion
Some travelers see their mobility increase even as roadway traf
c congestion
increases. They include those who move from the city to the suburbs and switch
from transit and walking to driving, and those who get their driving license as they
become of age.
10.4.3 Impacts of Traffic Congestion on the Mobility
of Transit Riders, Pedestrians, and Bicycle Users
10.4.3.1 Transit Riders
Because the out-of-vehicle travel time for transit riders is a large component of
door-to-door travel time (see Table
10.3
), network traf
c congestion which affects
primarily in-vehicle-travel time, tends to have a smaller impact on the mobility of
transit users than it has on that of automobile users.
10.4.3.2 Traffic Congestion Impact on the Mobility of Pedestrians
and Bicycle Users
Pedestrian and bicycle trips tend to be shorter than vehicle trips. Therefore traf
c
congestion tends to have a smaller impact on pedestrian/bicycle trip times than it
has on motorized vehicle trips.
10.5 Trends in Traffic Congestion and Traveler Mobility
The Texas Transportation Institute (TTI) annual metropolitan traf
c congestion
reports [
11
] indicate that traf
c congestion has been steadily increasing since 1980
—
except for the years of economic slowdown (see Chap.
6
). The news media and
elected/appointed of
cials rely on these annual reports to inform the public about
the increasing cost of traf
c congestion [
12
].
But according to the National Household Travel Survey [
13
] and reported by
Pisarski and Alan [
14
] increasing freeway/expressway traf
c congestion does not
seem to have reduced average traveler mobility (Table
10.5
).
