Civil Engineering Reference
In-Depth Information
Chapter 5
Concentration of Travel Demand in Space
and Time
5.1 Introduction
The concentrations of people and their activities (density) in space and in time are a
natural consequence of human behavior in urban areas.
If all travel demand were evenly distributed throughout the day, and among the
various parts of the urban area, the urban traf
c congestion problem would be greatly
reduced. But travel demand patterns re
ect where and
when
people live, work, and
play. Therefore, they are concentrated in space and time. It is these spatial and
temporal concentrations that contribute to the urban traf
fl
c congestion problem.
5.2 Concentration of Travel Demand in Space
Major activity and employment centers generate the highest concentration of traf
c
demand (trips ends per square mile) because of they are places of high development
densities (people/employees per square mile).
These centers include long established central business districts and the growing
number of large suburban centers. Suburban mega-centers, mainly automobile
dependent, generate heavy traf
c volumes on major arterials and approach roads
which are typically congested. And even where major centers are well served by
public transportation, traffic density is high, and congestion is also a problem.
5.2.1 The Central Business District
The central business district (CBD) is usually the single largest urban activity center
when measured by employment or
fl
floor space. It usually occupies an area of about
