Civil Engineering Reference
In-Depth Information
Table 13.6
Estimated impact of traf
c congestion on fuel consumption
Speed
(mph)
Fuel consumption
(gals./mile)
Source
Fig. 5.3
Additional fuel consumed
when speed changes from:
Additional fuel consumed
when speed changes from
5
0.100
45/55
-
5 mph = +0.067
gals./mile (+300 %)
15
-
5 mph = +0.055
gals./mile (+167 %)
15
0.045
45/55
15 mph = +0.012
gals./mile (+36 %)
-
-
45
55
0.033
-
-
-
Source
Estimated from Fig.
13.2
13.2.1.4 Some Examples of Reported Congestion Costs
This section gives some examples of the reported costs of traf
c congestion.
US Urbanized Areas
The cost of traf
c congestion in the US urban areas is reported annually by the
Urban Mobility Report (UMR) [
22
] and is widely quoted by the national press. The
UMR de
nes the time and fuel costs of congestion as:
Time and Fuel Costs
¼
½
ð
Actual Travel Time
Þ
ð
Free - Flow Travel Time
Þ
½
Value of Travel Time
þ
ð
Fuel Consumption in Actual Traffic Conditions
Þ
ð
Fuel Consumption in Free - Flow Conditions
Þ
½
½
Unit Cost of Fuel
ð
13
5
Þ
:
ow travel time as the threshold of congestion the following results
were documented for 2010:
Using free-
fl
In 2010, congestion caused urban Americans to travel 4.8 billion h more and to
purchase an extra 1.9 billion gallons of fuel.
Congestion causes the average urban resident to spend an extra 34 h of travel
time and use 14 extra gallons of fuel, which amounts to an average cost of $713
per commuter (Table
13.7
).
The value of wasted time, fuel and truck operating costs amounted to
$101 billion total congestion cost, $23 billion of which is due to truck
congestion.
The cost of congestion delay time calculated by the Urban Mobility Report
(UMR) is based upon the difference between actual travel time and free-
ow travel
time. However, this assumption over-states the cost of congestion for the following
reasons:
fl
(1)
In large urban areas, traf
c volumes in the rush hours cannot be expected to
travel at free-
ow conditions in large
metropolitan areas are practically impossible to achieve.
fl
ow speeds because peak period free-
fl
(2)
Increasing traf
c volume is the outcome of increasing social and economic
activity
—
a desired social goal. The added travel time from free-
fl
ow conditions
