Civil Engineering Reference
In-Depth Information
23.6 Estimating Ridership Response to Transit Service
and Fare Changes
Passenger response to fare and service changes have been observed in many transit
systems. Where service is improved, ridership has grown from two basic sources:
(a) from existing riders who use transit more frequently, and (b) from new riders
who previously used automobiles or walked. A convenient approach to estimating
the impact of fare and service changes on transit ridership is the pivot-point elas-
ticity method. Elasticity metrics indicate the responsiveness of ridership to changes
in fare and/or service for a time period when all other factors that affect travel
demand remain constant. They can provide realistic estimates of near term changes
in ridership from changes in service.
The concept of transportation elasticity is adapted from the economist
s measure
of price elasticity of a particular product or service. Ridership elasticity is de
'
ned as
the percentage change in ridership from a 1 % change in fares, service frequency, or
transit-miles operated.
Two commonly used methods to calculate elasticity are the
“
Shrinkage Factor
”
and
“
Arc Elasticity
”
.
has been commonly used to estimate a change in rid-
ership resulting from fare increase. Hence the term shrinkage re
The
“
shrinkage factor
”
ects the reduction
in transit rides from a fare increase. However, the shrinkage factor is also applied to
estimate ridership increase from a reduction in fare. It has been used as a
fl
“
rule of
thumb
in estimating the ridership effects of fare changes. It is the simplest method
to use and gives a reasonable approximation for small fare changes. It is also used
to estimate the change in ridership from changes in service (travel time, frequency,
etc.).
Shrinkage Ratio Elasticity = [(Change in Ridership/Base Ridership)]/[(Change
in Service Attribute (e.g. transit fare))/(Base Attribute (e.g., fare)]
Or
”
E ¼
½
ð
R2
R1
Þ=
R1
Þ
=
X2
X1
½
ð
Þ=
X1
ð
23
:
1
Þ
where:
E = elasticity
R1 = base ridership
R2 = calculated new ridership
X1 = value of base attribute (e.g., fare)
X2 = value of changed attribute (e.g., new fare)
Therefore:
R2 ¼ R1
þ
½
ðÞ
R
ðÞ
½
ð
X2
X1
Þ
=
X1
ð
23
:
2
Þ
