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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.