Civil Engineering Reference
In-Depth Information
exiting ramps to avoid delays to main line traf
c. However, most capacity additions
to urban systems resulted from building the untolled Interstate Highway System
that dramatically reduced urban traf
c congestion and improved mobility.
Increasing suburbanization of the population and employment in the ensuing dec-
ades soon produced traf
c demands that approached or exceeded the capacity of
many urban freeways. With freeway congestion increasing and as environmental
and social concerns about adding new capacity emerged, many cities looked for
other ways of improving mobility and reducing congestion
—
albeit for selected
users.
Since the 1970s US transportation agencies have made considerable efforts in
managing freeway congestion. Bus lanes and high-occupancy lanes were added on
many freeways. The Federal Highway Administration permitted tolls to be charged
on managed High Occupancy Toll Lanes (HOT Lanes) that were added to the
Interstate system and other freeways. The growing congestion on many urban
freeways has increased the need for reducing traf
c demand. With the emergent
advanced technologies (sensors, computing, communication), pricing strategies in
the form of
“
congestion pricing
”
or
“
value pricing
”
became very attractive strate-
gies to reduce congestion.
However, broad application of congestion pricing in the United States has been
limited because of continued political, institutional, and public resistance to the
concept. Therefore, most congestion pricing and other travel demand reduction
strategies are primarily found in Europe, South America, and Singapore.
19.3 Congestion Pricing
19.3.1 De
nition and Concerns
Congestion pricing is a way to reduce traf
c periods by
charging a fee (or toll) to road users. In economic terms it is the charging of higher
prices to reduce the consumption of roadway capacity
c demand during busy traf
—
especially when and where
congestion occurs. Congestion pricing is a new
“
usage
”
charge or tax that is applied
where demand exceeds capacity [
1
].
19.3.1.1 Basic Concept
To avoid adding new capacity that is only used part of the time, and to reduce
operating costs, variable charges have been used successfully to manage peak
demand in many sectors of the economy. It has been widely used by the telephone
and utility industries, airlines, railways, hotels, and even restaurants. The Wash-
ington DC metro system charges higher fares for peak hour trips and lower fares
during off peak periods.
