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48 Guidelines for Providing Access to Public Transportation Stations
bicycle-friendliness of an area contributes to bicycle access. The number of bicycle parking
spaces available was positively correlated with bicycle access but this may not reflect a causal
relationship, as agencies may be more likely to concentrate bicycle parking in areas with the
highest underlying demand.
· Pedestrian--Both employment density and population density are positively correlated with
increased pedestrian access trips. Note that worker density (i.e., the number of employed
residents) was found to be more strongly associated with pedestrian than simple population
density. In addition, walk access to transit was higher in places where pedestrian travel is more
common (measured by walking commuters), indicating the overall pedestrian-friendliness of
an area contributes to pedestrian access.
· Feeder Transit--The number of available transit connections is strongly associated with more
feeder transit access trips, as expected. Feeder transit access is also higher in areas of higher
population density (which are likely to support higher frequency feeder service) and at stations
with higher parking utilization (indicating that passengers may be more likely to switch to
feeder transit if parking is difficult to obtain).
Effects of Improved Station Access
There are many situations where it is desirable to improve access to an existing station. In
these cases, quantified estimates of usage, benefits, and costs should be developed. Relevant
information relating to existing station usage includes station boardings by time of day, modes
of travel used by boarding and alighting passengers, and off-street parking accumulations by time
of day. Information on bus routes, frequencies, and passenger loads should also be assembled.
Transit agencies often periodically collect this information, but when the information is not
already available, field studies should be conducted. Past trends in station boardings and access
modes should be analyzed. These can provide a basis for estimating likely future trends. Obtaining
population, worker, demographic and car ownership trends in a ½-mile (or sometimes 1-mile)
radius of the station will prove useful.
Park-and-Ride
Many park-and-ride facilities operate near, at, or beyond their capacities. This excess demand
can result in spillover parking impacts to surrounding neighborhoods and also inhibits ridership.
Where a station's park-and-ride facilities operate at or near capacity (i.e., over 90 percent occupancy),
providing more spaces will likely increase ridership. This has been the experience of both BART and
Metro-North.
Exhibit 5-4 summarizes Metro-North's experience in Connecticut. The net daily boarding
increase at the origin station per parking space added was 0.11 in New Haven, 0.60 in South
Norwalk, and 0.92 in Bridgeport. The exhibit suggests that up to one new rider can be gained
per parking space added. Of course, demand for parking is always finite, suggesting that agencies
should conduct a more thorough demand analysis in situations where parking is being expanded
significantly (e.g., an increase of more than 25 percent).
Some communities along Metro-North commuter lines manage parking. Often there are
waiting lists for reserved parking spaces. In similar situations, some or all of these parkers should
be added to the observed parking utilization for the purposes of demand estimation.
Pricing parking spaces provides an important means of recovering some of the initial devel-
opment costs and/or ongoing operating costs of the parking. However, charging for parking may
also reduce demand for parking and thus ridership. BART's experience has been that pricing
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Travel Demand Considerations 49
Exhibit 5-4. Changes in parking supply and demand at three
Connecticut stations.
New South
Bridgeport
Haven Norwalk
Time Period Studied 1985-1999 1996-1999 1985-1999
Parking Spaces Added +628 +325 +500
Additional Rail Ridership
Gross Ridership Increase +467 +250 +736
Ordinary Growth (estimated 1.5% / year) +400 +55 +277
Ridership Increase Attributed to Mode
+67 +195 +459
Shifts Induced by Parking ("New Riders")
Additional Rail Ridership per Parking Space
Added
Gross Ridership Increase / Space Added 0.74 0.77 1.47
"New Riders" / Space Added 0.11 0.60 0.92
Note: External factors affecting Bridgeport included lowered train fares, free parking at state lot,
and station area improvements.
Source: TCRP Report 95 (14, 16 )
parking has not reduced parking usage or rapid transit ridership; however, CBD parking costs
are relatively high in BART's service area. In general, park-and-ride demand is less likely to be
replaced when the CBD all-day parking charge is less than the round trip rapid transit fare plus
the daily parking charges at the station.
The effects of changing park-and-ride supply and pricing at BART stations are shown in
Exhibit 5-5. The various demand elasticities (shrinkage factors) shown in the exhibit provide a
basis for estimating the likely effects of changing parking supply and bus service. Note that when
parking is not fully utilized, pricing shows an elasticity of 0.33 (i.e., demand is reduced).
Where spaces are fully occupied, removing spaces would either increase parking spillover in
areas adjacent to the station or would reduce auto access trips and rapid transit ridership.
Exhibit 5-5. BART elasticities and defaults (shrinkage factors).
A. ELASTICITIES
1. Parking space is 90% utilized
no effect
Parking pricing
2. Parking space is less than 90% utilized
-0.33
Parking pricing
3. Feeder bus service hours +0.60
B. PERCENTAGE SHIFTS
1. Auto to Bus when Feeder Bus Service is increased 2%
2. Shift from auto to other when parking is removed (parking
34%
90% or more utilized)
3. Bus to auto when parking is added (parking 90% or more
34%
utilized)
Source: BART
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50 Guidelines for Providing Access to Public Transportation Stations
Transit Service Changes
Changes in feeder bus revenue miles, travel times, frequencies, and fares will also influence
ridership. Elasticity factors are commonly used to quantify these changes. Ridership elasticity
is defined as the change in ridership corresponding to a 1 percent change in bus fares, revenue
miles, travel times, or service frequency.
Elasticity Methods
Three types of methods can be used to compute elasticity: (1) shrinkage factors, (2) midpoint
linear arc elasticity and (3) log arc elasticity:
1. Shrinkage Factor. The shrinkage factor has been used as a "rule of thumb" for many years
to estimate the ridership effects of fare changes. It is the simplest method to apply and gives
a reasonable approximation for small fare changes. The percentage increase in ridership is
equal to the percentage change in an attribute (e.g., fare) times the appropriate elasticity factor.
The equations are as follows:
ER1 ( X 2 - X1 )
R2 = R1 +
X1
where:
E =elasticity
R1=base ridership
R2=estimated future ridership
X1=quantity of base attribute (such as travel time or frequency)
X2=quantity of future attribute
2. Midpoint (Linear) Arc Elasticity. This method is commonly used in estimating ridership
changes and is the method used in Chapter 5. It is defined as follows:
( E - 1) X1 R1 - ( E + 1) X 2 R1
R2 = = R1 F
( E - 1) X 2 - ( E + 1) X1
where:
E =elasticity
R1=base ridership
R2=estimated future ridership
X1=quantity of base attribute (such as travel time or frequency)
X2=quantity of future attribute
F =multiplier
3. Log Arc Elasticity. Log arc elasticities are another method of calculating elasticities, but has
seen relatively few transit applications. As such, the formulas are not reproduced here.
A comparison of three elasticity computation methods is shown in Exhibit 5-6. For small
changes (± 10 percent), the three methods give similar results. However, for large changes, results
obtained from the shrinkage factor diverge considerably from the other two methods. Therefore,
users of these methods should always be aware of the method originally used to develop the
elasticity factor and should use the corresponding calculation method when applying the factor.
Applications
The application of elasticity factors is straightforward. Typical midpoint elasticities (Method 2)
are shown in Exhibit 5-7. Where a transit agency has produced specific elasticity values, these
should be used instead.
