J Community Health DOI 10.1007/s10900-013-9785-7
ORIGINAL PAPER
Helmet Use Among Users of the Citi Bike Bicycle-Sharing Program: A Pilot Study in New York City Corey H. Basch • Danna Ethan • Sonali Rajan • Sandra Samayoa-Kozlowsky • Charles E. Basch
Ó Springer Science+Business Media New York 2013
Abstract The use of bicycle helmets to prevent or reduce serious head injuries is well established. However, it is unclear how to effectively promote helmet use, particularly in the context of bicycle-sharing programs. The need to determine rates of helmet use specifically among users of bicycle-sharing programs and understand if certain characteristics, such as time of day, affect helmet use, is imperative if effective promotion and/or legislative efforts addressing helmet use are to be developed. We estimated the prevalence of helmet use among a sample of Citi Bike program users in New York City. A total of 1,054 cyclists were observed over 44 h and across the 22 busiest Citi Bike locations. Overall, 85.3 % (95 % CI 82.2, 88.4 %) of the cyclists observed did not wear a helmet. Rates of helmet non-use were also consistent whether cyclists were entering or leaving the docking station, among cyclists using the Citi Bikes earlier versus later in the day, and among cyclists using the Citi Bikes on weekends versus weekdays. Improved understanding about factors that facilitate and hinder helmet use is needed to help reduce head injury risk among users of bicycle sharing programs.
C. H. Basch (&) S. Samayoa-Kozlowsky Department of Public Health, William Paterson University, Wing 150, Wayne, NJ 07470, USA e-mail: [email protected] D. Ethan Health Education and Promotion, Department of Health Sciences, Lehman College, The City University of New York, New York, NY, USA S. Rajan C. E. Basch Department of Health Education, Teachers College, Columbia University, New York, NY 10027, USA
Keywords Helmet use Bicycle-sharing New York City Citi Bike
Introduction Helmet use when cycling can reduce or prevent head injury [1]. A literature review identified five case control studies examining the relationship between helmet use and head injury. Specifically, the reduction of brain injury and other head injuries among cyclists wearing a helmet was 63–88 % [1]. The role of a biking helmet in preventing serious injury has been well established in the literature, and this knowledge has informed prevention programs, campaigns, and public service announcements targeting adults and children alike [2, 3]. The wide-spread efficacy of such efforts, however, appears to be mixed. Indeed, in New York City (NYC) in 2012 alone, there were 3,882 injuries and 18 fatalities involving crashes between cyclists and motor vehicles and 537 injuries or fatalities that did not involve motor vehicles [4]. And almost all (97 %) of the serious cycling injuries and fatalities in NYC between 1996 and 2005 occurred among cyclists who were not wearing a helmet [5]. A review of studies looking at bicycle legislation concluded that enacting legislation to mandate helmet use appears to be effective [6]. Yet legislative action remains controversial, particularly in the context of urban bicycle-sharing programs, as it is unclear how to mandate helmet use without also limiting those who take advantage of such initiatives. The need to determine rates of helmet use specifically among users of bicycle-sharing programs and understand if characteristics, such as day of week or time of day, affect helmet use, is therefore imperative if effective promotion and/or legislative efforts are ultimately to be developed.
123
123
83.3
67.5
Central Park South and 6th avenue
West Street and Chambers Street
86.2
Pershing Square North
(n = 29)
(n = 61)
88.5
88.5
96.7
Cleveland Place and Spring Street
(n = 26)
West Thames Street
(n = 61)
Centre Street and Chambers Street
(n = 117)
(n = 83) East 17th Street and Broadway
(n = 18)
(n = 24)
76.9
95.8
Murray Street and West Street
(n = 61)
77.0
80.0
87.9
University Place and East 14th Street
(n = 80)
(n = 33) Broadway and East 14th Street
West Houston Street and Hudson Street
(n = 16)
Old Slip and Front Street
81.3
80.0
West 41st Street and 8th Avenue
(n = 25)
Proportion of cyclists not using helmets (%)
Location (N)
90.1
94.1
100.0
93.3
74.1
77.1
100.0
100.0
73.1
79.5
84.2
80.0
84.6
Proportion of cyclists not using helmets while leaving the Citi Bike station (%)
71.4
81.5
82.3
100.0
79.7
54.3
81.3
92.9
77.8
80.5
92.9
83.3
75.0
Proportion of cyclists not using helmets while arriving at the Citi Bike station (%)
86.7
88.0
100.0
95.8
75.0
68.8
88.9
100.0
76.7
69.7
90.0
90.9
85.7
Proportion of cyclists not using helmets (8:00 AM–2:00 PM) (%)
Table 1 Proportion of Citi Bike users in New York city not using helmets overall, and by arriving/leaving docking station, and time of day
85.7
88.9
85.7
97.3
79.2
67.2
77.8
93.3
77.4
87.2
84.6
60.0
72.7
Proportion of cyclists not using helmets (2:00 PM–8:00 PM) (%)
J Community Health
82.8
Pershing Square South
87.1
85.1
73.9
89.7
88.2
West 33rd Street and 8th Avenue
Lafayette Street and East 8th Street (n = 101)
Broadway and West 24th Street
Christopher Street and Greenwich Street
8th Avenue and West 31st Street
84.5
85.3
(82.2, 88.4)
Broadway and East 22nd Street (n = 58)
Mean
(95 % CI)
(n = 36)
83.3
Broadway and West 57th Street
(n = 17)
(n = 107)
(n = 23)
(n = 31)
(n = 18)
94.4
West 21st Street and 6th Avenue
(n = 29)
Proportion of cyclists not using helmets (%)
Location(N)
Table 1 continued
(82.9, 90.5)
86.7
86.7
90.1
83.3
89.1
83.3
85.7
77.8
100.0
80.0
Proportion of cyclists not using helmets while leaving the Citi Bike station (%)
(77.5, 87.7)
82.8
82.1
71.4
100.0
90.1
63.6
84.4
100.0
87.5
88.9
Proportion of cyclists not using helmets while arriving at the Citi Bike station (%)
(79.2, 87.9)
83.6
78.8
78.9
87.5
86.0
62.5
81.0
81.3
90.0
76.2
Proportion of cyclists not using helmets (8:00 AM–2:00 PM) (%)
(81.7, 91.1)
86.4
92.0
88.2
89.0
93.0
100.0
88.1
93.3
100.0
100.0
Proportion of cyclists not using helmets (2:00 PM–8:00 PM) (%)
J Community Health
123
J Community Health
In 2013, the Citi Bike bicycle-sharing program was launched in NYC with 330 stations and nearly 6,000 bikes. Over 600,000 miles have since been traveled on Citi Bikes, which now has over 80,000 annual members [7]. The prevalence of helmet use among Citi Bike users, however, is unknown. The purpose of this pilot study was, therefore, to (1) estimate the prevalence of helmet use among a sample of Citi Bike users and (2) describe how this work may inform efforts to increase helmet use and reduce injuries and fatalities among riders in NYC.
Methods Three coders (C.H.B., D.E., and S.K.) conducted direct observations of helmet use at the 22 most popular Citi Bike docking stations, located in Manhattan and Brooklyn, NYC [8]. Between August and September 2013, the number of cyclists entering and leaving each Citi Bike docking station along with corresponding helmet use was recorded on two occasions for 1-h intervals between 8:00 AM–2:00 PM and 2:01 PM–8:00 PM. Only cyclists who removed or docked a Citi Bike were included in the study’s sample. The docking station was the unit of sampling and analysis. Mean prevalence of helmet use and 95 % confidence intervals were calculated across all docking stations. Estimates are presented for the overall sample, among cyclists entering and leaving the docking station, across each observed time frame, and among those cyclists participating on weekdays versus weekends. Data were analyzed in SPSS (version 21.0). The Institutional Review Boards at William Paterson University, Lehman College at the City University of New York, and Teachers College, Columbia University approved this study.
Results A total of 1,054 cyclists were observed, with 65.9 % of observation hours (n = 29) taking place on weekend days when Citi Bike use is greatest [9]. The median number of cyclists observed at each location was 32 (25th percentile = 24, 75th percentile = 66). Overall, 85.3 % (95 % CI 82.2, 88.4 %) of cyclists observed across the 22 sites were not wearing a helmet (Table 1). Despite the comparatively small sample, the 95 % confidence intervals indicate that the estimates were relatively precise. Further, the estimates were not found to be statistically significantly different for comparisons among cyclists entering (82.8 % [95 % CI 77.5, 87.7 %]) versus leaving (86.7 % [95 % CI 82.9, 90.5 %]) the docking station; among cyclists using the Citi
123
Bikes during the earlier (83.6 % [95 % CI 79.2, 87.9 %]) versus later 86.4 % [95 % CI 81.7, 91.1 %]) time frame; and among cyclists using the Citi Bikes on weekdays (82.0 % [95 % CI 76.7, 87.3 %]) versus weekends (86.4 % [95 % CI 82.2, 90.5 %]).
Discussion Despite the comparatively small sample size, this pilot study provides direct observations of the largest sample of bike sharing program users than any we found in the published literature. Consistent with prior studies in Toronto, Washington, D.C., and Boston [10, 11], our findings reveal that over 4 of 5 Citi Bike users do not wear a helmet and, further, helmet non-use rates are consistent across Citi Bike locations, time of day, and day of week. To the extent that these findings generalize to the 80,000 plus current Citi Bike users, they reveal a significant opportunity for prevention and reduction of cycling head injuries and fatalities. Increasing helmet use among bike sharing program users presents particular challenges. Boston’s bike sharing program includes a helmet requirement in its user agreement, but rates of use were similar to that observed in this study [12]. In other urban areas, only recommendations for wearing a helmet are offered [12]. Mandating use may significantly reduce participation in bike sharing programs, but we did not identify published research demonstrating this empirically. Indeed, we did not identify any published evaluative research on the effectiveness of any efforts to increase helmet use among bike sharing participants. Improved understanding about barriers to and strategies for increasing cycling helmet use is needed to inform efforts to increase awareness, interest, incentives and use of helmets. Given the low proportion helmet use among current Citi Bike participants, the success of such efforts will ultimately depend on social change in which using a helmet while cycling becomes normative behavior. There are substantive benefits of bike-sharing programs in urban areas (e.g., physical activity for users and reduced dependence on motorized transportation), yet there are considerable risks for injury when cycling in streets typically crowded with cars, trucks, buses, and taxi cabs, as well as other cyclists, runners and pedestrians (who are frequently in a rush and distracted by use of mobile phones). As innercity bike sharing programs grow in popularity and proliferate, substantive efforts aimed at individuals and environmental changes to increase cycling helmet use are needed. Unfortunately, at this time such efforts appear to be sparse.
J Community Health
References 1. Thompson, D., Rivara, F., Thompson, R. (2009). Helmets for preventing head and facial injuries in cyclists. Cochrane Database of Systematic Reviews. 12, 1–33, CD001855. 2. Bicycle Helmet Safety Institute. Public Service Announcements. Retrieved from: http://www.helmets.org/psa.htm. 3. Cusimano, M. D., Faress, A., Luong, W. P., Lockhart, S., Amin, K., Garland, R. J., et al. (2013). Evaluation of a bicycle helmet safety program for children. Canadian Journal of Neurological Sciences, 40(5), 710–716. 4. New York City Department of Transportation. Bicycle crash data 2012. The City of New York. Retrieved from: http://www.nyc. gov/html/dot/downloads/pdf/2012-bicycle-crash-data-report.pdf. Published January 1, 2012. 5. Nicaj, L., Mandel-Ricci, J., Assefa, S., et al. Bicyclist fatalities and serious injuries in New York City: 1996–2005: a joint report from the New York City Departments of Health and Mental Hygiene, Parks and Recreation, Transportation, and the New York City Police Department. The City of New York. Retrieved from: http:// www.nyc.gov/html/dot/downloads/pdf/bicyclefatalities.pdf.
6. MacPherson, A., Spinks, A. (2008). Bicycle helmet legislation for the uptake of helmet use and prevention of head injuries. Cochrane Database of Systematic Reviews, 12, 1–19. CD005401. 7. Citi Bike. System data. Citi Bike. Retrieved from: http:// citibikenyc.com/system-data. 8. Citi Bike. Blog. Citi Bike. Retrieved from: http://citibikenyc. com/blog. 9. Guerriero, M. The New Yorker. Interactive: A month of CitiBike. Retrieved from: http://www.newyorker.com/online/blogs/newsdesk/ 2013/07/month-of-citi-bike.html. 10. Fischer, C. M., Sanchez, C. E., Pittman, M., Milzman, D., Volz, K. A., Huang, H., et al. (2012). Prevalence of bicycle helmet use by users of public bikeshare programs. Annals of Emergency Medicine, 60(2), 228–231. 11. Bonyun, M., Camden, A., Macarthur, C., & Howard, A. (2012). Helmet use in BIXI cyclists in Toronto, Canada: an observational study. BMJ Open, 18(2), 3. 12. McKernan, B. Associated Press. No helmets required for bike share in busy NYC. Retrieved from: http://bigstory.ap.org/article/ no-helmets-required-bike-share-busy-nyc-0#prclt-ndLyCy1j.
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ORIGINAL PAPER
Helmet Use Among Users of the Citi Bike Bicycle-Sharing Program: A Pilot Study in New York City Corey H. Basch • Danna Ethan • Sonali Rajan • Sandra Samayoa-Kozlowsky • Charles E. Basch
Ó Springer Science+Business Media New York 2013
Abstract The use of bicycle helmets to prevent or reduce serious head injuries is well established. However, it is unclear how to effectively promote helmet use, particularly in the context of bicycle-sharing programs. The need to determine rates of helmet use specifically among users of bicycle-sharing programs and understand if certain characteristics, such as time of day, affect helmet use, is imperative if effective promotion and/or legislative efforts addressing helmet use are to be developed. We estimated the prevalence of helmet use among a sample of Citi Bike program users in New York City. A total of 1,054 cyclists were observed over 44 h and across the 22 busiest Citi Bike locations. Overall, 85.3 % (95 % CI 82.2, 88.4 %) of the cyclists observed did not wear a helmet. Rates of helmet non-use were also consistent whether cyclists were entering or leaving the docking station, among cyclists using the Citi Bikes earlier versus later in the day, and among cyclists using the Citi Bikes on weekends versus weekdays. Improved understanding about factors that facilitate and hinder helmet use is needed to help reduce head injury risk among users of bicycle sharing programs.
C. H. Basch (&) S. Samayoa-Kozlowsky Department of Public Health, William Paterson University, Wing 150, Wayne, NJ 07470, USA e-mail: [email protected] D. Ethan Health Education and Promotion, Department of Health Sciences, Lehman College, The City University of New York, New York, NY, USA S. Rajan C. E. Basch Department of Health Education, Teachers College, Columbia University, New York, NY 10027, USA
Keywords Helmet use Bicycle-sharing New York City Citi Bike
Introduction Helmet use when cycling can reduce or prevent head injury [1]. A literature review identified five case control studies examining the relationship between helmet use and head injury. Specifically, the reduction of brain injury and other head injuries among cyclists wearing a helmet was 63–88 % [1]. The role of a biking helmet in preventing serious injury has been well established in the literature, and this knowledge has informed prevention programs, campaigns, and public service announcements targeting adults and children alike [2, 3]. The wide-spread efficacy of such efforts, however, appears to be mixed. Indeed, in New York City (NYC) in 2012 alone, there were 3,882 injuries and 18 fatalities involving crashes between cyclists and motor vehicles and 537 injuries or fatalities that did not involve motor vehicles [4]. And almost all (97 %) of the serious cycling injuries and fatalities in NYC between 1996 and 2005 occurred among cyclists who were not wearing a helmet [5]. A review of studies looking at bicycle legislation concluded that enacting legislation to mandate helmet use appears to be effective [6]. Yet legislative action remains controversial, particularly in the context of urban bicycle-sharing programs, as it is unclear how to mandate helmet use without also limiting those who take advantage of such initiatives. The need to determine rates of helmet use specifically among users of bicycle-sharing programs and understand if characteristics, such as day of week or time of day, affect helmet use, is therefore imperative if effective promotion and/or legislative efforts are ultimately to be developed.
123
123
83.3
67.5
Central Park South and 6th avenue
West Street and Chambers Street
86.2
Pershing Square North
(n = 29)
(n = 61)
88.5
88.5
96.7
Cleveland Place and Spring Street
(n = 26)
West Thames Street
(n = 61)
Centre Street and Chambers Street
(n = 117)
(n = 83) East 17th Street and Broadway
(n = 18)
(n = 24)
76.9
95.8
Murray Street and West Street
(n = 61)
77.0
80.0
87.9
University Place and East 14th Street
(n = 80)
(n = 33) Broadway and East 14th Street
West Houston Street and Hudson Street
(n = 16)
Old Slip and Front Street
81.3
80.0
West 41st Street and 8th Avenue
(n = 25)
Proportion of cyclists not using helmets (%)
Location (N)
90.1
94.1
100.0
93.3
74.1
77.1
100.0
100.0
73.1
79.5
84.2
80.0
84.6
Proportion of cyclists not using helmets while leaving the Citi Bike station (%)
71.4
81.5
82.3
100.0
79.7
54.3
81.3
92.9
77.8
80.5
92.9
83.3
75.0
Proportion of cyclists not using helmets while arriving at the Citi Bike station (%)
86.7
88.0
100.0
95.8
75.0
68.8
88.9
100.0
76.7
69.7
90.0
90.9
85.7
Proportion of cyclists not using helmets (8:00 AM–2:00 PM) (%)
Table 1 Proportion of Citi Bike users in New York city not using helmets overall, and by arriving/leaving docking station, and time of day
85.7
88.9
85.7
97.3
79.2
67.2
77.8
93.3
77.4
87.2
84.6
60.0
72.7
Proportion of cyclists not using helmets (2:00 PM–8:00 PM) (%)
J Community Health
82.8
Pershing Square South
87.1
85.1
73.9
89.7
88.2
West 33rd Street and 8th Avenue
Lafayette Street and East 8th Street (n = 101)
Broadway and West 24th Street
Christopher Street and Greenwich Street
8th Avenue and West 31st Street
84.5
85.3
(82.2, 88.4)
Broadway and East 22nd Street (n = 58)
Mean
(95 % CI)
(n = 36)
83.3
Broadway and West 57th Street
(n = 17)
(n = 107)
(n = 23)
(n = 31)
(n = 18)
94.4
West 21st Street and 6th Avenue
(n = 29)
Proportion of cyclists not using helmets (%)
Location(N)
Table 1 continued
(82.9, 90.5)
86.7
86.7
90.1
83.3
89.1
83.3
85.7
77.8
100.0
80.0
Proportion of cyclists not using helmets while leaving the Citi Bike station (%)
(77.5, 87.7)
82.8
82.1
71.4
100.0
90.1
63.6
84.4
100.0
87.5
88.9
Proportion of cyclists not using helmets while arriving at the Citi Bike station (%)
(79.2, 87.9)
83.6
78.8
78.9
87.5
86.0
62.5
81.0
81.3
90.0
76.2
Proportion of cyclists not using helmets (8:00 AM–2:00 PM) (%)
(81.7, 91.1)
86.4
92.0
88.2
89.0
93.0
100.0
88.1
93.3
100.0
100.0
Proportion of cyclists not using helmets (2:00 PM–8:00 PM) (%)
J Community Health
123
J Community Health
In 2013, the Citi Bike bicycle-sharing program was launched in NYC with 330 stations and nearly 6,000 bikes. Over 600,000 miles have since been traveled on Citi Bikes, which now has over 80,000 annual members [7]. The prevalence of helmet use among Citi Bike users, however, is unknown. The purpose of this pilot study was, therefore, to (1) estimate the prevalence of helmet use among a sample of Citi Bike users and (2) describe how this work may inform efforts to increase helmet use and reduce injuries and fatalities among riders in NYC.
Methods Three coders (C.H.B., D.E., and S.K.) conducted direct observations of helmet use at the 22 most popular Citi Bike docking stations, located in Manhattan and Brooklyn, NYC [8]. Between August and September 2013, the number of cyclists entering and leaving each Citi Bike docking station along with corresponding helmet use was recorded on two occasions for 1-h intervals between 8:00 AM–2:00 PM and 2:01 PM–8:00 PM. Only cyclists who removed or docked a Citi Bike were included in the study’s sample. The docking station was the unit of sampling and analysis. Mean prevalence of helmet use and 95 % confidence intervals were calculated across all docking stations. Estimates are presented for the overall sample, among cyclists entering and leaving the docking station, across each observed time frame, and among those cyclists participating on weekdays versus weekends. Data were analyzed in SPSS (version 21.0). The Institutional Review Boards at William Paterson University, Lehman College at the City University of New York, and Teachers College, Columbia University approved this study.
Results A total of 1,054 cyclists were observed, with 65.9 % of observation hours (n = 29) taking place on weekend days when Citi Bike use is greatest [9]. The median number of cyclists observed at each location was 32 (25th percentile = 24, 75th percentile = 66). Overall, 85.3 % (95 % CI 82.2, 88.4 %) of cyclists observed across the 22 sites were not wearing a helmet (Table 1). Despite the comparatively small sample, the 95 % confidence intervals indicate that the estimates were relatively precise. Further, the estimates were not found to be statistically significantly different for comparisons among cyclists entering (82.8 % [95 % CI 77.5, 87.7 %]) versus leaving (86.7 % [95 % CI 82.9, 90.5 %]) the docking station; among cyclists using the Citi
123
Bikes during the earlier (83.6 % [95 % CI 79.2, 87.9 %]) versus later 86.4 % [95 % CI 81.7, 91.1 %]) time frame; and among cyclists using the Citi Bikes on weekdays (82.0 % [95 % CI 76.7, 87.3 %]) versus weekends (86.4 % [95 % CI 82.2, 90.5 %]).
Discussion Despite the comparatively small sample size, this pilot study provides direct observations of the largest sample of bike sharing program users than any we found in the published literature. Consistent with prior studies in Toronto, Washington, D.C., and Boston [10, 11], our findings reveal that over 4 of 5 Citi Bike users do not wear a helmet and, further, helmet non-use rates are consistent across Citi Bike locations, time of day, and day of week. To the extent that these findings generalize to the 80,000 plus current Citi Bike users, they reveal a significant opportunity for prevention and reduction of cycling head injuries and fatalities. Increasing helmet use among bike sharing program users presents particular challenges. Boston’s bike sharing program includes a helmet requirement in its user agreement, but rates of use were similar to that observed in this study [12]. In other urban areas, only recommendations for wearing a helmet are offered [12]. Mandating use may significantly reduce participation in bike sharing programs, but we did not identify published research demonstrating this empirically. Indeed, we did not identify any published evaluative research on the effectiveness of any efforts to increase helmet use among bike sharing participants. Improved understanding about barriers to and strategies for increasing cycling helmet use is needed to inform efforts to increase awareness, interest, incentives and use of helmets. Given the low proportion helmet use among current Citi Bike participants, the success of such efforts will ultimately depend on social change in which using a helmet while cycling becomes normative behavior. There are substantive benefits of bike-sharing programs in urban areas (e.g., physical activity for users and reduced dependence on motorized transportation), yet there are considerable risks for injury when cycling in streets typically crowded with cars, trucks, buses, and taxi cabs, as well as other cyclists, runners and pedestrians (who are frequently in a rush and distracted by use of mobile phones). As innercity bike sharing programs grow in popularity and proliferate, substantive efforts aimed at individuals and environmental changes to increase cycling helmet use are needed. Unfortunately, at this time such efforts appear to be sparse.
J Community Health
References 1. Thompson, D., Rivara, F., Thompson, R. (2009). Helmets for preventing head and facial injuries in cyclists. Cochrane Database of Systematic Reviews. 12, 1–33, CD001855. 2. Bicycle Helmet Safety Institute. Public Service Announcements. Retrieved from: http://www.helmets.org/psa.htm. 3. Cusimano, M. D., Faress, A., Luong, W. P., Lockhart, S., Amin, K., Garland, R. J., et al. (2013). Evaluation of a bicycle helmet safety program for children. Canadian Journal of Neurological Sciences, 40(5), 710–716. 4. New York City Department of Transportation. Bicycle crash data 2012. The City of New York. Retrieved from: http://www.nyc. gov/html/dot/downloads/pdf/2012-bicycle-crash-data-report.pdf. Published January 1, 2012. 5. Nicaj, L., Mandel-Ricci, J., Assefa, S., et al. Bicyclist fatalities and serious injuries in New York City: 1996–2005: a joint report from the New York City Departments of Health and Mental Hygiene, Parks and Recreation, Transportation, and the New York City Police Department. The City of New York. Retrieved from: http:// www.nyc.gov/html/dot/downloads/pdf/bicyclefatalities.pdf.
6. MacPherson, A., Spinks, A. (2008). Bicycle helmet legislation for the uptake of helmet use and prevention of head injuries. Cochrane Database of Systematic Reviews, 12, 1–19. CD005401. 7. Citi Bike. System data. Citi Bike. Retrieved from: http:// citibikenyc.com/system-data. 8. Citi Bike. Blog. Citi Bike. Retrieved from: http://citibikenyc. com/blog. 9. Guerriero, M. The New Yorker. Interactive: A month of CitiBike. Retrieved from: http://www.newyorker.com/online/blogs/newsdesk/ 2013/07/month-of-citi-bike.html. 10. Fischer, C. M., Sanchez, C. E., Pittman, M., Milzman, D., Volz, K. A., Huang, H., et al. (2012). Prevalence of bicycle helmet use by users of public bikeshare programs. Annals of Emergency Medicine, 60(2), 228–231. 11. Bonyun, M., Camden, A., Macarthur, C., & Howard, A. (2012). Helmet use in BIXI cyclists in Toronto, Canada: an observational study. BMJ Open, 18(2), 3. 12. McKernan, B. Associated Press. No helmets required for bike share in busy NYC. Retrieved from: http://bigstory.ap.org/article/ no-helmets-required-bike-share-busy-nyc-0#prclt-ndLyCy1j.
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