California Public Electric Vehicle Charging Stations’ Accessibility to Amenities

https://chenjeremy015.carto.com/builder/b695f2f2-3a1e-11e7-9549-0ecd1babdde5/embed
SELECT  
stations.*
FROM
alt_fuel_stations_may_3_2017 as stations,
ne_50m_admin_1_states as CA
WHERE
CA.name = 'California'
AND
ST_Contains(
CA.the_geom, stations.the_geom
)
Process: For this step, since the concentrated study area is California, I narrowed down the U.S. public charging stations to only charging stations within the California using ST_Contains.
https://chenjeremy015.carto.com/builder/14928f78-3a79-11e7-bc9f-0e3ebc282e83/embed
SELECT
stations.*
FROM
ca_public_charging_stations_mcdonald_s AS stations,
ca_mcdonalds_2014 AS Mcdonalds
WHERE
ST_DWithin(
stations.the_geom_webmercator,
mcdonalds.the_geom_webmercator,
1609/4
)
https://chenjeremy015.carto.com/builder/f8839a2e-3a7e-11e7-ac76-0e3ebc282e83/embed
SELECT
stations.*
FROM
ca_public_charging_stations_starbucks AS stations,
ca_starbucks_2014 AS starbucks
WHERE
ST_DWithin(
stations.the_geom_webmercator,
starbucks.the_geom_webmercator,
1609/4
)
Process: This step contains using the ST_DWithin spatial transform function to find public charging stations that are accessible (within 0.25 miles distance) to McDonald's and Starbucks.
https://chenjeremy015.carto.com/builder/f43eff60-3a94-11e7-ac37-0e233c30368f/embed
SELECT
ST_Buffer(
the_geom_webmercator,
1609/4
) AS the_geom_webmercator,
cartodb_id
FROM
ca_public_charging_stations
Process: Using the ST_Buffer, I created 0.25 miles distance buffer for each of the public charging station.
Story:    
California is one of the leading states on the adoption of electric vehicles (EVs) and has the most public electric vehicle charging stations (EVCSs) available for use. For instance, between 2010 and 2016, roughly 223,000 plug-in electric vehicles (PEVs) were purchased in California (CEC, 2016). In addition, the Pacific Gas and Electric plans to implement 7,500 EV charging ports in Northern California after receiving the permission (The Pacific Gas and Electric Company, 2016).
With the increase of EVs on the roads, additional EVCSs will be needed for EV drivers to utilize. As people see charging stations more frequently in the public, it will build up their confidence in the capability of EVs. Additionally, it will reduce and prevent range anxiety of EV drivers, which is when they fear that the battery of their EVs will run out before reaching their destinations (Dong, 2014).
However, before implementing EVCSs in the public, there are various criteria that need to be considered such as the suitability of the location to have electric grid or locations that are prone to natural disaster (Vermont Energy Investment Corporation, 2014). One of these criteria is public EVCSs' accessibility to amenities. When people are charging their EVs that require a significant amount of waiting time, have amenities nearby will provide them with the option to do activities that are worthwhile.
To examine the accessibility of California public EVCSs to amenities, CARTO was used along with manipulating SQL queries to generate web map representations that answer the following research question:
    Are existing California public EVCSs accessible to amenities within a proper walking distance of 0 to 0.25 miles?

The first web map shows California public EVCSs with additional information such as the location and available charger types. A total of 3,667 EVCSs was examined. Next, the second and third maps show the public EVCSs that are within 0.25 miles of McDonald's and Starbucks. The maps also illustrate that 391 and 1,365 EVCSs were accessible (within 0.25 miles) to McDonald's and Starbucks, respectively. McDonald's and Starbucks were studied as the amenities for this research because the two places are well-known and widely available in California. According to Yang and Diez-Roux (2012), the 0.25 miles is a commonly used tolerable walking distance of people in U.S. research. The results demonstrate that California public EVCSs are not tremendously accessible to the amenities of McDonald's (11%) and Starbucks (37%). However, the results do show that charging stations are relatively accessible to Starbucks than to McDonald's. Lastly, the fourth map exhibits buffers of 0.25 miles around the public EVCSs. This map is an alternative way to investigate the accessibility of EVCSs, which allow people to see if there are amenities within the 0.25 miles buffer zone.
Understanding current public EVCSs' accessibility to amenities is important because it allows us to know if the charging stations are suitably placed. As stated earlier, having EVCSs is crucial for EV drivers. Moreover, for future planning on locating optimal charging station sites, this study would be a great example on how to examine the accessibility of EVCSs to amenities.
Limitations:
The study only examined two amenities, which do not account for all of the possible amenities. This is due to limited time and data that I could find. Another limitation is that the data for the locations of McDonald's and Starbucks were created in 2012, which do not completely represent the current available McDonald's and Starbucks. The locations of public EVCS data was downloaded on May 3rd, 2017.
References:
CEC. (2016). California Energy Commission – Tracking Progress. Sacramento. Retrieved from http://www.energy.ca.gov/renewables/tracking_progress/documents/electric_vehicle.pdf
Dong, J., Liu, C., & Lin, Z. (2014). Charging infrastructure planning for promoting battery electric vehicles: An activity-based approach using multiday travel data. Transportation Research Part C: Emerging Technologies, 38, 44–55. https://doi.org/10.1016/j.trc.2013.11.001
The Pacific Gas and Electric Company. (2016). Decision Directing Pacific Gas and Electric Company to Establish an Electric Vehicle Infrastructure and Education Program. San Frnacisco. Retrieved from http://docs.cpuc.ca.gov/PublishedDocs/Published/G000/M171/K213/171213824.PDF
Vermont Energy Investment Corporation. (2014). Electric Vehicle Charging Station Guidebook: Planning for Installation and Operation. Chittenden County RPC. Burlington. https://doi.org/10.1109/TSG.2014.2344684
Yang, Y., & Diez-Roux, A. V. (2012). Walking Distance by Trip Purpose and Population Subgroups. American Journal of Preventive Medicine, 43(1), 11–19. https://doi.org/10.3174/ajnr.A1650.Side
Data sets:
1. California Public Electric Vehicle Charging Station locations data set was acquired from Alternative Fuels Data Center of U.S. Department of Energy.
2. McDonald's restaurant locations and Starbucks store locations data sets were originally acquired from ArcGIS.
3. U.S. states data set was acquired from CARTO data set library.
**This research, besides the CARTO and SQL portions, is all based on my master's project; therefore, all of the information are from that paper.
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