The effect of park-n-rides on greenhouse gas emissions

Material Information

The effect of park-n-rides on greenhouse gas emissions
Truong, Lisa C. ( author )
Place of Publication:
Denver, CO
University of Colorado Denver
Publication Date:
Physical Description:
1 online resource (44 pages). : ;

Thesis/Dissertation Information

Master's ( Master of Science)
Degree Grantor:
University of Colorado Denver
Degree Divisions:
Department of Civil Engineering, CU Denver
Degree Disciplines:
Civil Engineering
Committee Chair:
Marshall, Wesley E.
Committee Members:
Janson, Bruce
Hayes, Roxann


Subjects / Keywords:
Fringe parking ( lcsh )
Greenhouse gas mitigation ( lcsh )
Fringe parking ( fast )
Greenhouse gas mitigation ( fast )
bibliography ( marcgt )
theses ( marcgt )
non-fiction ( marcgt )


Over the past decade, rising greenhouse gas emissions (GHG emissions) have put public transit in the forefront of sustainable transportation. To improve transit accessibility and attract riders, Park-n-Ride (PnR) facilities have been built on the periphery of cities. By providing convenient parking facilities, agencies encourage drivers to shift modes in their single occupancy vehicle (SOV) and complete their journey by transit. While PnRs are intended to facilitate more transit riders, the facilities may also carry paradoxical consequences. Do PnRs actually reduce the distance traveled by SOVs? Does a multi-modal trip offset emissions from a theoretical SOV drive-only trip? Critics have challenged the environmental efficiency of PnRs, claiming the magnitude of the modal shift may not necessarily be reflected in GHG emissions. Drivers may still make long trips by car to reach the PnR. This study evaluates the magnitude of GHG emissions saved from transit ridership, based on SOV PnR users in the Denver metro area. By comparing the multi-modal trip against a theoretical SOV drive-only trip, the effects from GHG emissions are weighed. Theoretically, the further a person drives to reach a PnR, the less of an impact transit has on reducing GHG emissions. Results showed that PnRs located at inner-corridor stations are less effective at reducing GHG emissions than end of line stations. PnRs near downtown provide an incentive for longer SOV drives. Consequently, drivers who make long transit access trips can outweigh the benefits of transit usage due to increased vehicle emissions.
Thesis (M.S.)--University of Colorado Denver. Civil engineering
Includes bibliographic references.
General Note:
Department of Civil Engineering
Statement of Responsibility:
by Lisa C. Truong.

Record Information

Source Institution:
|University of Colorado Denver
Holding Location:
|Auraria Library
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
868584423 ( OCLC )


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THE EFFECT OF PARK N RIDES ON GREENHOUSE GAS EMISSIONS by LISA C. TRUONG B.S., Colorado School of Mines, 2011 A thesis submitted to the Faculty of the Graduate School of the University of Colorado in partial fulfillment of the requirements for t he degree of Master of Science Civil Engineering 2013


ii This thesis for the Master of Science degree by Lisa C. Truong has been approved for the Civil Engineering Program by Wesley E. Marshall, Chair Bruce Janson Roxann Hayes April 16, 2013


iii Truong, L isa C. (M.S., Civil Engineering) The Effect of Park n Rides on Greenhouse Gas Emissions Thesis directed by Assistant Professor Wesley E. Marshall ABSTRACT Over the past decade, rising greenhouse gas emissions (GHG emissions) have put public transit in the forefront of sustainable transportation T o impro ve transit accessibility and attract riders, Park n Ride (P n R) facilities have been built on the periphery of citie s. By providing convenient parking facilities agencies encourage drivers to shift modes in their single occupancy vehicle (SOV) and complete their journey by transit. W hile PnRs are intended to facilitate more transit riders the facilities may also carry paradoxical consequences. Do PnRs actually reduce the distance traveled by SOVs? Do es a multi modal trip offset emissions from a theoretical SOV drive only trip? Critics have challenged the environmental efficiency of PnRs, claiming the magnitude of the modal shift may not necessarily be reflected in GHG emissions. Drivers may still ma ke long trips by car to reach the PnR. This study evaluate s the magnitude of GHG emissions saved from transit ridership based on SOV PnR users in the Denver metro area By comparing the multi modal trip against a theoretical SOV drive only trip, the e ffects from GHG emissions are weighed The oretically, the further a person drive s to reach a P n R, the less of an i mpact transit has on reducing GHG emissions Results showed that PnRs located at inner corridor stations are less effective at reducing GH G emissions than end of line stations. PnRs near downtown provide an


iv incentive for longer SOV drives. Consequently, drivers who m ake long transit access trips can outweigh the benefits of transit usage due to increased vehicle emissions The form and co ntent of this abstract are approved. I recommend its publication. Approved: Wesley E. Marshall


v DEDICATION To my mother and father, John and Nancy Truong, who have always supported me endlessly in my education from kindergarten through graduate school. To my boyfriend, Ricky Nguyen, who has supported me through my research and long nights of studyin g, and is never shy of joining me on a multi modal adventure. Finally, to all of my mentors, bosses, and friends in the transportation industry thank yo u for inspiring a life long passion.


vi ACKNOWLEDGEMENTS I would like to thank Dr. Wesley Marshall for serving as my graduate advisor and providing invaluable advice for my thesis. I also thank Dr. Bruce Janson and Roxann Hayes for their encouragement a nd wisdom shared through transportation courses as well as serving on my Thesis Committee Finally, I want to thank Lee Cryer from RTD FasTracks for providing the 2008 RTD On Board Survey used in the study Ignacio Correa Ortiz of RTD for providing the R TD Sustainability Survey, and the DRCOG Sustainable Communities Initiative for supporting this research


vii TABLE OF CONTENTS CHAPTER I. INTRODUCTION ........ 1 II. BACKGROUND AND LITERATURE REVIEW .. III. STUDY OVERVIEW 8 Data Methodology Calculating vehicle and transit mileage ... ... 12 Calculating GHG emissions 6 Carbo n dioxide ratio: Multi 7 IV. RESULTS 1 9 V DISCUSSION 2 4 2 5 .. .. 2 6 Imp roving transit access trip with walking 2 7 V I. CONCLUSION 31 REFERENCES .... 34


viii LIST OF TABLES T able 1: PnR parking availability and station typology 8 2: Greenhouse Gas Impacts from RTD LRT System, 2009 1 7 3: Transit access trip statistics 19 4: Average distances for Multi Modal and Theoretical SOV trip 20 5: GHG emission s ummary and CO 2 equivalent ratio 21 6: Driving trips <2 miles replaced by walking/biking 2 8


ix LIST OF FIGURES F igure 1 : Origin and destination summary for Nine Mile Station PnR 1 1 2 : Example of multi 1 4 3 : Example of SOV drive 1 5 4: Average CO 2 equivalent ratio by station 23 5: PnR Transit Alternative Que stion 24 6: Walk/bike vs. SOV drive CO 2 equivalent ratio ........... 2 9


1 CHAPTER I INTRODUCTION C oncerns about environmental sustainability have led to an increased consciousness in seeking more sustainable transp ortation. A good portion of the carbon footprint derive s from transport activities, making it more important than ever to reduce single occupancy vehicles (SOV s ), utilize alternative modes of transportation and reduce vehicular emissions In cities with congested urban corridors and lim ited parking capacity, park n ride ( PnR ) facilities have become a popular measure toward increasing transit ridership PnR facilities allow for commuters to park their vehicles and transfer onto larger feeder system s goin g into the metro area. Serving as a magnet to draw more drivers out of their cars and into public transit, Pn R s can improve the accessibility of transit. While there are several studies that discuss the effects of public transit on environmental sustai nability, there is little literature that explores the link between Pn R an d greenhouse gas emissions (GHG emissions ). In theory, vehicle emissions shoul d decrease as drivers shift their mode to public transit. Although the e nvironmental effects from a lo ne driver may seem marginal, the sum of a larger grou p utiliz ing Pn R facilit ies mul tipl ies these effects. A modal shift from SOV to mass public transit can add up quickly and since m any Pn Rs are located within suburbs and on the periphery of cities they often provid e a common access point that facilitates transit to riders along the most congested portions of their trip. T hus, t he effects from transit usage may add up to a reduction in the overall carbon footprint as compared to fully SOV driven trip s As a result, p ublic transit has been touted as one of the most effective means in reducing GHG


2 emissions from SOV s because shifting modes from private vehicles to public transit creates displaced car trip that correspond wit h displaced vehicle miles trave led (VMT). While P n Rs are designed to facilitate maximum transit usage, they may also carry paradoxical environmental consequences. The magnitude of the modal shift may not necessarily be reflected in significant GHG emissions reductions as drivers cou ld be driv ing a long portion of the trip by car. In other words, a ndividual choices may not necessarily in the best interests of the environment Placed against driving a rational individual might only use a P n R if its generalized cost is low er than the one for the drive only trip (J. Holguin Veras et al., 2012). For example, avoiding parking costs may be primary reason for taking transit; th erefore, free parking becomes the motivator In the context of individualized costs, a dr iver is more likely to use a free PnR when the drive only trip carries parking fees. In fact, driver s may go out of their way to access a PnR facility if doing so results in a significant savings in parking costs. These challenges, amongst others, make the environmental effects from P n Rs multi faceted and in need of further study This thesis will seek to better understand the relationship between PnRs and GHG emissions through a case study of Denver, Colorado Using data from the Regional Transporta tion District (RTD) of Denver and the Denver Regional Council of Governments (DRCOG), t he study will analyze trip patterns for SOV PnR light rail users across metro Denver. Trip distances will be determined for the multi modal trip, including a SOV transi t access portion and a light rail portion, as well as the calculated hypothetical SOV drive only trip distance Using these distances, the study estimates the GHG emissions saved by riders using PnRs and light rail transit with respect to their


3 relative e ffect on the overall commute Because carbon dioxide (CO 2 ) is the main element in transport based GHG emissions, CO 2 equivalents will be used to measure the environmental effects of each mode. Theoretically, riders create the most environmental benefits when the transit access trip is shorter than the light rail trip, reducing vehicular emissions from an SOV drive only trip while still providing convenient access to the PnR facility. In a broader scope, this study will add to the larger library of litera ture examining how public transportation usage can affect the environment.


4 CHAPTER II BACKGROUND AND LITERATURE REVIEW P n R facilities have become highly popular in the United States and Europe. These car ports intercept motorists heading into the city a nd provide transfers onto bus, rail, or carpool for the remainder of their journey. P n R facilities integrate the private auto into the public transport system, allowing for drivers to evade the low speeds of inner city driving, the inevitable congestion d elays, and the high costs of parking in the city. P n Rs can improve accessibility to transit while creating more parking availability outside the urban corridor. Most metropolitan areas suffer from heavy traffic congestion and have limited parking capacit y ; building new parking facilities and structures can be limited by physical constraints. P n Rs allow for parking capacity to increase without locating the structures in congested city center s The P n R system is well suited for suburban commuters because the auto portion of the trip provides connectivity to the P n R site, while the transit portion enables riders to reach their final destination at a minimal social cost (Holguin, 2012). Riders are afforded an opportunity to avoid the most congested portion of the commute and can save money in parking costs Additionally, transit agencies can focus operations on segments of the network with the most sufficient demand, as opposed to providing multiple local feeders. Transportation policy makers tend to favor P n Rs, as they are generally saleable to the public (Karamycheve, 2011) and can help increase transit ridership fairly quickly The facilities expand choice s for transport options and provide an opportunity for alternative modes without forcing people com pletely out of their cars. However, the broader issue at hand is not whether people shift modes; the pro blem lies in whether there is a reduction in the amount of energy used and greenhouse gases emitted.


5 In a recent Brookings Institution report (Brow n, Southworth et al., 2008), transit rich regions were found to have a lower carbon footprint. Land use in these regions tended to be more mixed use and compact developments, qualities found in transit oriented developments (TODs). Residents of TODs tend to own fewer vehicles, drive less, walk more, and have better access to transit. On a national scale, the American Public Transportation Association (APTA) quantified emissions displaced by transit through avoided car trips at 16 million metric tons (MMT ) of CO 2 equivalent per year, offset by 12 MMT CO 2 emissions produced by transit (Bail ey 2007; Davis and Hale 2007); thus, there was a net savings of 4 MMT CO 2 emissions. Logically, if P n Rs are being used efficiently and effectively there would be a redu ction in vehicular emissions As evidenced in academic literature, the large passenger capacity of public transit can allow for a sizable reduction in GHG emissions produced by SOV s Although P n Rs are a popular gateway to increasing transit ridership there are limited publications that explore the sustainability effects from these facilities. Do P n R facilities reduce the miles driven by SOVs ? The impacts on the environment are rather uncertain. Several arguments challenge the environmental efficie ncy of these facilities. First, the magnitude of the modal shift may not necessarily reflect on GHG emissions ; a potentially long part of the trip can still be made by car (Gantele, 2008). Transit access trips are generally longer than the trip leg betwe en the P n R location and the urban center (Parkhurst, 2000, Meet et al., 2008b). P n Rs may induce unexpected and counterproductive effects, such as commuters who reach the train station by car instead of walking or biking Additionally by facilitating acce ssibility P n R facilities may potentially attract new driving trips thus having a negative effect on vehicle emissions.


6 Finally, the long term effects of P n R s may help proliferate urban sprawl by creating more vehicle accessibility outside the city cente r (Gantele, 2008) Paradoxically, each of these potential impacts raises challenge s for P n Rs in fulfilling their sustainable purpose A study from the Swiss Federal Office of Energy (Guillaume Gentil et al., 2004) reported mixed results for Swiss P n R s in regard to environmental efficiency. Notably, P n Rs located near city centers turn out to be counterproductive, while P n Rs along regional transport networks showed better energy efficiency. Overall, the results of the Swiss study were inconclusive The methods used for the study in Switzerland encompass several aspects that affect environmental sustainability, including the cost efficiency, the effects on roadway congestion, and the availability of long term parking in metro areas. While the study cove rs multiple issues, it is difficult to determine any true findings as many of the factors were inconclusive. For this study, the primary focus will be to highlight GHG emissions in terms of CO 2 equivalents. More recently, a research study from the Ne th er lands found that PnRs may create unintended effects which not only limit transit usage but may even increase vehicle travel in the metro area. The primary consequence was where individuals shifted to driving from tra nsit that had been previously been making the entire trip via public transit before the PnR was introduced (Mingardo 2013 ). Other unintended consequences include additional trip generation, abstraction from bike, and park and walk issues. Abstraction fr om bike describes individuals who once made all or some of their commute by bike and now drove to the station. Park and walk depicts people who parked at the station but then walked somewhere nearby and did not use transit at all (Jaffe 2013 ). Such user s potentially displace transit riders who use


7 the PnR for transit access. Each of these unintended consequences raised concerns about negative environmental impact from PnRs. Surveys from the Netherlands also asked how users would make the same trip in t he absence of the PnR. Of these 39.2% claimed they would not make the trip whatsoever The methodology behind this study interviewed 738 PnR users in Rotterdam ; whereas the Denver survey analyzed in this study looks at over 2 000 responses. From the Rot terdam pool, only 47.3% of users took the PnR for work related activities. While the Dutch study provides interesting insights for European PnRs at rail based stations, there is a lack of literature studying the environmental effects from American based P nRs. As car ownership and vehicle emissions continue to rise, alternative transportation is struggling to keep pace in counterbalancing the environmental impacts As a result, it is important to know whether or not P n R facilities can help mitigate GHG emissions. PnRs seem promising, as they tend to capture drivers outside the most congested roads and provide a valuable travel link for their trips. Although commuters still make a portion of their trip by private vehicle, the net effects of a large grou could However, the literature shows that there is reason to doubt these benefits. Within this study, the effect of P n Rs on GHG emissions will be studied more closely, seeking to find if the net benefits from transit usage can outweigh private vehicle usage.


8 CHAPTER III STUDY OVERVIEW As of 2012, RTD operate s 74 P n R facilities in the Denver metro region. Of these, nineteen P n Rs provide li ght rail transit (LRT) services. Tab le 1 provides a listing of parking spaces provided at each station, from least to greatest, as well as the station typology. Parking for a station serving residential neighborhood has different demands than a station in a TOD/mixed use area. Table 1 : P nR parking availability and station typology Light Rail Station # of Parking Spaces Station Type 30th & Downing 27 Residential Orchard 48 Commercial Belleview 59 Commercial Evans 99 Residential Yale 129 Residential Dry Creek 235 TOD/Mixed use Dayton 250 Residential Alameda 302 Commercial County Line 338 Commercial Littleton Downtown 361 TOD/Mixed use Colorado 363 Commercial University 540 School Southmoor 788 TOD/Mixed use Arapahoe at Village Center 817 TOD/Mixed use Englewood 910 TOD/Mixed u se Nine Mile 1225 Commercial Littleton Mineral 1227 TOD/Mixed use I 25 & Broadway 1248 TOD/Mixed use Lincoln 1734 TOD/Mixed use Parking fees for P n R usage are based upon whether a vehicle is registered within the RTD district. In district residents may park at the P n R facility for free during the first 24 hours; after this period, a fee of $2 per day is assessed. Out of district residents are


9 charged a fee of $4 per day. Exemptions for out of district vehicle fees applies to active duty U.S. milit ary assigned in Colorado, college students enrolled in at least 10 credit hours attending class at least three days a week, drivers of vehicles with a valid disable placard or license plate, and residents who recently moved into the district and have fille d an exemption application. Data In 2008, RTD conducted an on board survey of its riders in the D enver metro area. The survey, administered by NuStats, was conducted on local, limited, express, regional, SkyRide, and all light rail routes. Data were collected during the months of February, March, and April 2008, resulting in a total of 23,865 usable surveys. Riders were surveyed for the immediate one way trip. Surveyors were asked to provide information about their transit access trip, mode of acces s, origin and destination, and transit route. Additionally, surveyors were asked various socio economic questions, fare payment method and what alternative mode would have been taken if transit was not available. According to NuStats, samples from all m ajor bus and light rail routes are at the 95% confidence level. Before selecting the 2008 RTD on board survey as the data set for this study, many other options for transit ridership patterns were considered. The RTD Annual License Plate survey provide s an annual study of PnR users by origin. The license plate survey is primarily targeted toward seeing how far drivers commute to the PnR, as well as tracking out of district users. Any out of district commuters are charged daily fees to use the PnR; the cameras used for this survey provide frequent enforcement of this


10 policy. Unfortunately, the license plate survey lacked destination data for the specific riders. An attempt was made to connect RTD boardings/alighting information to fill the destination void. However, in order to perform this analysis, many layers of assumptions would need to be made. Finally, the more recent DRCOG Regional Travel Survey was obtained in an effort to obtain more accurate origin destination data for PnR users. Unfortuna tely, while the data is coded for transit users, the database does not specify bus from light rail. Thus, it would have been difficult to determine the distance traveled by transit, since bus routes and light rail lines vary. The 2008 RTD on board survey provided a total of 2,019 surveyors who accessed PnR facilities by SOV and rode light rail for a portion of the commute. Results for transit access trip distance varied across the region; for end of the line stations (such as Nine Mile and Lincoln), driv ers tended to be from more geographically scattered areas. Fig ure 1 shows a map with the origin and destination of surveyors accessing Nine Mile PnR. Data points from the origin and destination summary were used in analysis of GHG emissions, as described in the Methodology section. Results of the data analysis can be found in the following section.




12 Methodology Calculating vehicle and transit mileage This study utilize s data collected from board s urvey to gau ge ridership patterns and P n R behavior at light rail stations in the Denver metro region. In order to obtain an applicable set of data, several filters were applied to the original set of 23,865 surveys. To compare the effects of P n R providing transit ac cess to drivers, the set was isolated for SOVs accessing the P n R. This provided information to estimate the vehicle miles travel (VMT) displaced by light rail. The filtered data set contains 2 019 surveyed riders who fall within the criteria above. Usin g the truncated data, calculations were made to determine the approximate distance riders traveled during their commute. Because the survey asked riders about their immediate one way trip, some trips were home based whi le others were work based; nonethele ss, all trips contained a transit portion and a vehicle portion. The car based portion of the trip is transit The following procedure was used to determine the mileage of each trip: 1. Transit access t rip mileage was provided by the surveyors and verifi ed through Google Maps. 2. Transit miles traveled was determined as the distance between the boarding station (PnR location) and the ali ghting station ( destination) This is also referred to as the light rail trip segment.


13 3. SOV mileage for the hypothetical drive only trip is estimated by entering the origin and destination addresses in Google Maps The Google Maps program calculates the best routes bas ed upon shortest distance and shortest drive time. As shown below Figure 2 rail trip (steps 1 and 2 in procedure). Figure 3 provides an example using the same theore tical SOV drive only trip.






16 Calculating GHG emissions Vehicle emissions from the transit access trip and theoretical drive only SOV trip are calculated b y usin methodology for quantifying GHG emissions from transit. The national default value for fleet fuel economy is 20.2 miles per gallon, as reported by the EPA in Light Duty Automotive Technology and Fu el Economy Trends: 1973 through 2007 (Equation 1) From the fuel consumed of the displaced VMT carbon dioxide emissions are obtained by using the national default values for GHG emissions as reported from The Climate Re gistry General Reporting Protocol v. 1.0, Tables 13.1 and 13.4. Carbon dioxide is the primary GHG emitted through human based transportation activities; thus, carbon dioxide emissions will be the primary GHG emission measured in this study. The default v alue for carbon dioxide emissions is : (Equation 2 ) Environmental impacts from transit are determined from the 2009 RTD Sustainability Survey. GHG impacts f or light rail are based upon electricity usage (kilowatts) used for the traction power supply system (TPSS). Additionally, energy usage for other LRT system components, including power for signal houses and stations,


17 are included in the LRT GHG impacts. Table 2 GHG impact, as well as the carbon dioxide equivalent per passenger mile. Table 2 : Greenhouse Gas Impacts from RTD LRT System, 2009 LRT System Component Electricity Usage (kWh) CO 2 Equivalent ( kg CO 2 ) T ractio n power system supply 43,766,810 32,695 ,000 Communication signal house 1,450,420 1,023 ,000 LRT s tation power usage 8,817,095 6,221 ,000 LRT s tation lighting 44,509 31 ,000 T otal CO 2 Equivalent from LRT system 39,970 ,000 Annual LRT Passenger Miles (200 9) 129,248,691 CO 2 equivalent per Passenger Mile 0.3092 T he carbon dioxide equivalent per passenger mile in Denver was calculated to be 0.3092. In comparison, a national found the average of CO 2 emissions per passenger mile on light rail to be 0.202 ranging between 0.113 to 1.689 (M.J. Bradley). Travel Matters, part of the Transportation Research Board, determined the average CO 2 equivalent per transit mile to be 0.35 (TravelMatters). Thus, a value of 0.3092 is in line with national averages for GHG emissions in transit. The carbon dioxide equivalent per passenger mile is used to determine how the actual transit miles traveled impacts the environment, as calculated in equation 3 : (Equation 3 ) Carbon dioxide ratio : Multi modal trip vs. SOV trip By using the GHG emission calculations f or vehicles and transit, a ratio of the ca rbon dioxide emissions from a multi modal trip to a SOV trip is determined. This ratio calculates the effect of using light rail relative to a fully SOV drive only trip by


18 incorporating the emissions from all modes in the multi modal and fully SOV trip A ratio that is less than 1.0 indicates that the multi modal trip emits fewer GHG emissions. As the ratio value approaches 1.0, the less er the effect transit has on emissions. If the ratio is greater than 1.0, then the multi modal trip is producing more emissions than an SOV drive only trip. In this scenario, it would be more environmentally sustainable to not take public transit. (Equation 4 )


19 CHAPTER IV RESULTS Using survey data from the 2008 RTD on board survey, travel patterns were analyzed for 2,019 SOV drivers who used PnRs in the Denver metro region. A summary of the transit acces s statistics is show n in Table 3 Table 3 : Transit access trip s tatistics Light Rail Station # of Parking Spaces Average Distance (mi) Minimum Distance (mi) Maximum Distance (mi) 30th & Downing 27 5.6 0.8 15 .4 Orchard 48 3.4 0.9 23 .2 Belleview 59 2.8 0.9 15 .1 Evans 99 2.9 1.0 11 .3 Yale 129 3.4 1 .1 13 .0 Dry Creek 235 3.6 0.9 15 .0 Dayton 250 7.3 0.7 26 .2 Alameda 302 5.6 1.0 30 .3 County Line 338 7.8 1 .0 20 .1 Littleton Downtown 361 4.0 1 .0 15 .0 Colorado 363 3.5 1 .2 20 .2 University 540 4.4 1.1 21 .3 Southmoor 788 4.2 1 .3 15 .1 Arapahoe at Village Center 817 5.2 1 .2 22 .3 Englewood 910 6.0 1.0 25 .0 Nine Mile 1225 5.4 1 .3 21 .4 Littleton Mineral 1227 5.0 1.1 25 .1 I 25 & Broadway 1248 7.3 1.2 30 .4 Lincoln 1734 6.7 0 .9 30 .3 As mentioned in the previous section, Nine Mile station (located at the end of the line) tends to attract a wide range of driver origins, shown in Figure 3 The average distance a commuter drives to reach Nine Mile PnR is 5.4 miles. However, some commuters drive up to 21 miles to reach the statio n compared to a light rail trip of only 14 miles. Light rail stations that were more centrally located within the corridor tended to have a lower


20 average driving distance. At Evans Station, the maximum transit access trip was 11 miles, with an average d istance of 2.9 miles Trip patterns were determined for both the multi modal trip, including a SOV transit access portion and a light rail portion, as well as for the theoretical SOV drive only trip. A summary of average distances for trips is shown in Table 4 Table 4 : Average distances for Multi Modal and Hypothetical SOV trip Light Rail Station Multi modal trip Hypothetical SOV drive only (mi) Transit access trip (mi) Transit miles traveled (mi) 30th & Downing 5.6 3.8 9.3 Orchard 3.4 11.7 15.1 Belleview 2.8 12.0 14.8 Evans 2.9 5.7 8.6 Yale 3.4 8.0 11.4 Dry Creek 3.6 15.0 18.6 Dayton 7.3 13.0 20.3 Alameda 5.6 8.1 13.8 County Line 7.8 16.5 24.3 Littleton Downtown 4.0 10.0 14.0 Colorado 3.5 7.6 11.1 University 4.4 5.6 10.0 Southmoor 4.2 9.4 13.5 Arapahoe at Village Center 5.2 14.0 19.1 Englewood 6.0 7.5 13.5 Nine Mile 5.4 13.9 19.3 Littleton Mineral 5.0 11.9 16.9 I 25 & Broadway 7.3 5.0 12.3 Lincoln 6.7 16.4 23.1 Based upon the distance of the tr ips, a carbon dioxide ( CO 2 ) eq uivalent was calculated for each mode as described in the methodology Vehicle emissions we re determined by using the national average fuel economy and converting into CO 2 equivalents ( Equation s 1 and 2 ). Light rail impacts are calculated from a factor o f CO 2


21 equivalent per passenger mile ( Equation 3 ). With all of the CO 2 equivalents determined, a ratio of multi modal trip to SOV trip was calculated. Equation 4 details the calculations for the CO 2 ratio. Primarily, this ratio was used to determine the relative effect of transit on GHG emissions. Table 5 provides results of the GHG emission analysis, including the average of emissions for each station and the CO 2 equivalent ratio. Table 5 : GHG emission summary and CO 2 equivalent ratio Light rail statio n Transit access emissions (kg CO 2 ) Light rail impact (kg CO 2 ) SOV drive only emissions (kg CO 2 ) CO 2 Ratio 30th & Downing 2.4230 1.1681 4.0706 0.88 Orchard 1.4762 3.6153 6.5756 0.77 Belleview 1.2176 3.7104 6.4512 0.76 Evans 1.2783 1.7592 3.7598 0. 81 Yale 1.4992 2.4736 4.9883 0.80 Dry Creek 1.5860 4.6380 8.1280 0.77 Dayton 3.2009 4.0196 8.8707 0.81 Alameda 2.4601 2.5074 5.9969 0.83 County Line 3.3993 5.0927 10.5828 0.80 Littleton Downtown 1.7290 3.0920 6.0904 0.79 Colorado 1.5192 2.3551 4.8411 0.80 University 1.9113 1.7233 4.3421 0.84 Southmoor 1.8211 2.8967 5.9070 0.80 Arapahoe at Village Center 2.2565 4.3154 8.3435 0.79 Englewood 2.6297 2.3249 5.9090 0.84 Nine Mile 2.3613 4.3043 8.4327 0.79 Littleton Mineral 2.1656 3.6920 7.3732 0.79 I 25 & Broadway 3.1763 1.5554 5.3702 0.88 Lincoln 2.9166 5.0657 10.0619 0.79 The closer a CO 2 equivalent ratio is to 1.0, the lesser the benefit transit has on the environment. Conversely, stations with lower ratios would have a greater environ mental benefit from transit. In theory, drivers who make longer transit access trips may be negating the positive environmental effects from transit usage, due to the greater SOV


22 usage over longer distances. From the ratio s it i s observed that some stat ions have a disproportionately higher amount of SOV transit access miles Many of the drivers who parked at 30 th & Downing station did not originate from nearby neighborhoods. B ecause this station provides free parking and is located within two miles of the downtown central business district (CBD) it lures drivers who would otherwise make a full y car based trip into downtown. In this scenario, the P n R serves pri marily to save the driver on costs of parking downtown. The graph in Figure 4 provides a gra phical analysis of the CO 2 ratios, organized in ascending order of parking spaces provided Of the stations with highest ratios, 30 th & Downing and I 25 & Broadway station are among the closest PnRs to downtown Denver. Parking fees provide a disincenti ve for drivers to park downtown, while still maximizing the utility of driving as close as possible to a free parking lot. In this sense, the PnR does not serve a purpose of encouraging sustainable transit ridership I nstead, the PnR facility actually in duces driving to the closest free parking possible. These effects are contrary to the overall intent of PnRs. Although these lots are intended to provide better access to public transit, drivers may still make long trips to reach the PnR facility and the refore negate the environmental benefits of using transit.




24 CHAPTER V DISCUSSION Do PnR facilities increase transit ridership? T he 2008 RTD on board survey asked riders how they would have made t heir trip if transit was not available. Out of the 2019 drivers who used the P n R, over 88% claimed that they w ould have otherwise driven alone for the full trip, shown in Figure 5 Thus, it would be fair to assume that because a P n R facility was availabl e, this made public transit more accessible to drivers. Most of individuals who have access to a private vehicle, but have chosen to switch modes in favor of public transit. What makes these riders significant is that alternatively, these same individuals would have been driving the roads in a lone occupant vehicle Not only would this increase congestion to roadway networks, but GHG emissions from transportation would also rise Figure 5 : P n R Tr ansit Alternative Question


25 Parking fees Parking fees can influence where a driver parks or which mode a rider chooses to take. In the downtown Denver central business district, parking is priced at premium, averag ing $ 16 per day (Denver Business Journal) This incentivizes commuters traveling into the downtown Denver CBD to seek alternative modes and/or free periphery parking. The other large employment center in the Denver metro region is the Denver Tech Center, located south of I 25 and I 225. Althou gh the southeast corridor caters to riders commuting through the DTC, there is a disparity in transit ridership because of free parking Because parking within the DTC is free of charge, employees have less incentive to leave their vehicles behind and com mute by transit. A survey of Denver businesses within one mile of light rail stations found that more than 80% of businesses outside the downtown CBD had free parking right next to their building (DRCOG). The abundance of free parking outside of downtown adds to the disincentive of riding transit. A notable observation from this study is the parking patterns of Castle Rock drivers. Castle Rock, located 31 miles south of downtown Denver, is not within the RTD district. Because its residents do not pay RTD taxes, riders from Castle Rock must pay to park at all times. Without the first 24 hours free, like other RTD in district residents enjoy, Castle Rock residents may feel an incentive to find free neighborhood or street side parking. The closest RTD light rail station with direct street side parking is at Belleview Station. Belleview is located six miles from Lincoln Station, meaning that drivers are willing to commute an extra 12 miles a day roundt rip in order to save on the $2 per day parking fee.


26 Parking d emand Prior to construction, parking estimates were determined based upon the DRCOG Regional Travel Demand Model. During the environmental evaluation process, stakeholders had an opportunity to provide input and feedback on the proposed parking lots/structures. Some lots, such as Evans Station, were influenced heavily by community comment and local political will. During the design process, 100 spaces were added to address concerns regarding spillover parking into adjacent residential areas (R TD). The concerns of residents within the Evans Station area were not isolated many other stations experienced similar push back from community members during preliminary development (RTD) Remarkably the only station on the Southeast corridor without a PnR is at Louisiana Pearl Station. Transit planners had designed this locati on to provide walk up service at a neighborhood based station It is the only light rail station on the corridor without a parking facility, in spite of its location at the hea rt of two Denver neighborhoods Despite the lack of parking provided, ridership at Louisiana/Pearl station is consistently high and has made the station one of the busiest stops outside of central downtown The distance to the next closest PnR facility f rom Louisiana Pearl is I 25/Broadway Statio n, located 0.8 miles away. The close proximity of these light rail stations to one another lends to the broader topic of station typology and station planning. Planners should be weary of placing a PnR facility at every station along the corridor for the sake of providing parking; in the larger scope of TOD planning and development, mixed developments may struggle if parking is over abundant. By limiting PnRs to selective locations where the demand is highest, s uch as at the end of station lines, corridors can provide more concentrated funnels for drivers to access the corridor from


27 PnRs. This will not only decrease the need for lower demand inner corridor parking lots, but will provide better parking efficiency at the primary lots. Improving transit access trips with walking/biking What if all commuters driving less than two miles to a PnR walked or biked to the station? What would be the effects on GHG emissions? After the primary analysis and results for t he study were obtained, a secondary analysis of the data was run to determine how many PnR users are driving less than two miles. A standard of two miles was selected based upon national TOD practices for an acceptable biking/walking distance for the aver age healthy adult. From here the GHG emissions analysis was re run with the assumption that each of these drivers would be able to walk or bike to the light rail station. A new CO 2 equivalent ratio for the multi modal trip versus SOV drive only trip was found using similar methodology as before In this case, the multi modal trip included a walking/biking portion to access the light rail station and the original light rail trip shown in Equation 5 A summary of these results follows in Table 6 and Fi gure 6 (Equation 5 )


28 Table 6 : Driving trips < 2 miles replaced by walking/biking Light Rail Station % of Drivers <2 mi Transit access emissions saved Walk/Bike CO 2 Ratio SOV Driver CO 2 Ratio % Change 30th & Downing 22% 3.49 0.29 0.88 67% Orchard 46% 5.23 0.55 0.77 29% Belleview 42% 8.72 0.58 0.76 25% Evans 41% 10.47 0.47 0.81 42% Yale 31% 8.72 0.50 0.80 38% Dry Creek 18% 10.47 0.57 0.77 25% Dayton 5% 2.62 0.45 0.81 44% Alameda 19% 10.47 0.42 0.83 50% County Line 6% 1.74 0.48 0.80 40% Littleton Downtown 16% 20.06 0.51 0.79 36% Colorado 30% 15.70 0.49 0.80 39% University 38% 22.68 0.40 0.84 53% Southmoor 30 % 29.66 0.49 0.80 39% Arapahoe at Village Center 22% 13.08 0.52 0.79 34% Englewood 11% 21.81 0.39 0.84 53% Nine Mile 6% 11.34 0.51 0.79 35% Littleton Mineral 8% 26.17 0.50 0.79 37% I 25 & Broadway 14% 12.21 0.29 0.88 67% Lincoln 8% 16.57 0.50 0.79 37 %




30 As seen in Figure 6 when the SOV t ransit access trip is substituted for walking or biking the positive environmental effects of transit increase Stations near downtown, such as 30 th & Down ing and I 25 &Broadway, exhibit the most change. Because walking and biking produce zero GHG emissions, the trip is even more sustainable than before End of line stations tend to have a more drivers commuting a farther distance, while inner corridor sta tions have a higher percentage of drivers commuting under two miles. This implies that inner corridor stations may not be highly effective in facilitating sustainable transport, and instead, encouraging short vehicular trips that could otherwise have been made by walking or biking. Applying this concept to a broader scope, what would happen if light rail stations provided adequate biking and walking facilities within the station area? Perhaps drivers who otherwise would have driven to the PnR would now b e able to walk or bike. It is important that light rail facilities provide access to multiple modes. While PnRs are popular with drivers and allow for convenient access by automobile, the parking facility may also induce additional traffic. By providing adequate, safe facilities for pedestrians and cyclists, light rail stations become more accessible by alternative modes. In effect, these active modes of transportation may actually reduce PnR congestion and minimize the need for commuters to drive short distances to parking.


31 CHAPTER VI CONCLUSION PnR facilities are intended to increase transit ridership by providing convenient, free parking access to suburban commuters. However, PnRs may also produce unintended consequences. As shown by the resul ts of this study, drivers can still make long trips to reach the PnR commuting up to 30 miles to reach a lot The vehicular emissions from th e s e long, SOV transit access trip s may negate the environmental benefits from using public transit. Illustrated by the CO 2 equivalent ratio, multi modal trips that include a long SOV drive portion actually emit almost as many GHG emissions as a SOV drive only trip. Thus, when a commuter makes a long drive to reach the PnR facility, the positive environmental effect s of using light rail are nominal. On the other end of the driving spectrum, PnR facilities may also induce additional driving trips. As observed in the secondary analysis, up to 46% of PnR users drove less than two miles to reach the parking facility. Shorter drives of less than two miles could be substituted with walking and biking Using an active mode of transport produces zero emissions, and allows for the overall trip to become even more sustainable more the environment. However, when parking is over abundant, users become less inclined to walk and bike to the stations, and instead, make a short driving trip, which is counterproductive in to the overall goal of a sustainable environment. On a regional level, when drivers shift modes to incorpora te transit in to their commute, the community should benefit from a net reduction in greenhouse gas emissions. According to the DRCOG Congestion Database, the Denver region VMT for 2008 is 73.4 million VMT per day. Transferring this figure into CO 2 emissi ons, the


32 Denver region would benefit from a 2% reduction in CO 2 emissions from PnR users. While this figure appears to be a minor reduction, it actually grows larger when considering all transit users, including those who do not use PnRs. From the analys is CO 2 equivalent ratios, the results of this study found that end of line stations were amongst the more sustainable locations for PnRs. T he geographic locations of these PnRs allow commuter s to ride a longer distance on the light rail than if they were to drive closer into downtown Nine Mile, Lincoln, and Littleton Mineral stations are all end of line points for their respective corridors, and each station had a CO 2 equivalent ratio of 0.79. In comparison, 30 th & Downing and I 25 & Broadway had a CO 2 equivalent ratio of 0.88. The higher ratio indicates that stations near downtown are less effective in facilitating sustainable habits. Providing free, convenient parking near downtown can be counteractive, such that drivers are provided an incentive to make a longer drive by car and shorter trip by transit. In order to promote the most sustainable transportation system possible, transit agencies should heavily consider the implications of parking supply and parking demand in station design. Further more the cost of parking should be factored into the management of PnRs; providing free parking encourages drivers to disregard added miles and emissions to the trip. PnRs need to foster sustainable transportation, and currently, some lots may be underpriced for the market. Moving forward, additional study can be done to evaluate how P n Rs affect other modes of transit, including bus transit. The GHG emissions and environmental impact of buses are different than LRT, which may provide interesting in sight for fleet management and vehicle technologies. Buses typically have a higher CO 2 equivalent per passenger mile because of diesel based fuels.


33 There is still much more work to be done in advancing sustainable transportation and off setting GHG emiss ions by transport. Looking forward, the role of PnRs in transit corridors should be one that complements sustainable transportation patterns. Instead of placing a PnR facility at each station, planners and stakeholders should consider a strategy that foc uses on how PnRs can be most effective. Inner corridor stations, particularly those closest to the downtown area, should be weary of creating induced traffic with parking facilities. End of line stations may be more effective in funneling suburban riders and maximizing their distance on transit. When used effectively, these facilities can provide a valuable tool to increase ridership and reduce GHG emissions. PnR facilities have played an important role in attracting choice riders from suburban areas, a nd allowing them a means to incorporate transit within their commute patterns. As more people become comfortable in using alternative transportation, the transport patterns of society will begin to shift, leading to a more sustainable tomorrow.


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