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Bicyclist Acute Stress and the Road Environment
A. Macmillan, J. Woodcock / Journal of Transport & Health 3 (2016) S4–S61
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S25
Bicyclist Acute Stress and the Road Environment
Dillon Fitch, Susan Handy University California Davis, CA, USA
Abstract Background: Bicycling is a moderate to vigorous form of physical activity, and thus has the potential to mitigate numerous chronic diseases thought to be influenced by sedentary life-styles. There is a growing consensus that promotional programs, land use planning, and restrictions on car use are important for increasing bicycling for directed travel. Nonetheless, road improvements have been one of the most strategic investment tools local and regional governments have to promote bicycling. Although there is plenty of evidence that infrastructure investments correlate with bicycling and that people prefer bicycle specific infrastructure, there still exist many questions surrounding comfort of road environments. By estimating the relationship between the road environment, perceived comfort, and psychological stress, we can improve our understanding of how to create comfortable road environments for bicycling which might encourage more people to consider bicycling as a normal mode of travel. In this paper, we present preliminary pilot results from an on-going experiment with continuous measures of bicyclist acute stress in a naturalistic bicycling task. Methods: This paper starts to fill this gap by reporting an in-depth study relating the road environment, perceived comfort, and psychophysiological measures of acute stress in college students in Davis, California. The study includes a quasi-experimental cross over (within subject) designed experiment of real world bicycling across numerous road conditions. Subject acute stress is measured physiologically through a heartbeat-to-beat measuring device (an approach often labeled heart rate variability (HRV) analysis), and subject anxiety and comfort are measured through traditional survey instruments. Results: Initial pilot data suggests a highly variable influence of the road environment on subject acute stress with individual differences in standard deviation of adjacent heart beat intervals (SDNN) ranging from 12% to 50% for low stress vs. high stress bicycling conditions. Nonlinearities were observed throughout pilot testing, and were most commonly associated with stopping at traffic signals, which showed variations in HRV in the range of 15-50%. Conclusions: Preliminary results are suggestive that HRV exhibits a psychological stress response associated with the road environment. Considerable individual differences suggest consistent group effects are unlikely to be found, and further investigation into the riding vs. approach/stop at intersections is needed. In addition, ongoing data collection will yield a larger sample of participants and warrant formal statistical analyses. http://dx.doi.org/10.1016/j.jth.2016.05.065
A35 Exposure-Based Crash Rates for Bicycle and Motorized Transport in Central Lane Metropolitan
Planning Organization Josh Roll Central Lane MPO, OR, USA
Abstract Background: Motor vehicle crashes continue to be one of the leading causes of death and disability in the United States. While population based crash rates allow for comparisons across modes and geographies to assess the burden upon the population, they do not evaluate risk. Vehicle miles traveled are typically used to normalize traffic crashes to better understand risk by allowing for exposure based rates. Similar rate calculations are rare for bicycle crash analysis due to limited bicycle traffic volume data. This work summarizes the methods used to calculate bicycle miles traveled and subsequent bike crash rates in the Eugene-Springfield, Oregon region. Methods: A facility demand model using negative binomial regression specification is used to estimate bicycle miles traveled in the EugeneSpringfield, Oregon region. These bike miles traveled estimates are then used to calculate exposure based bicycle crash rates for three injury severity levels. Bicycle crash rates are then compared to motorized vehicle crash rates using a similar exposure based rate calculation. Results: Comparison of exposure based crash rates for bicycle and motorized transport reveal significant differences with bicycle crash rates many times higher than motorized transport rates. These differences exist across all injury severity levels. Comparison of crash rates for different street designs show differences as well, intuitively revealing streets with higher vehicle speeds and higher vehicle volumes have higher crash rates for bikes and vehicles alike. Bike lanes seem to offer significant protection for people who ride bikes, though crash rates on these facilities are still higher than most facility combinations for motor vehicles. Conclusions: On average 10% of the fatal and severe injuries in the Eugene-Springfield metro area involve people riding bicycles. Due to this relatively low share of overall crash outcomes, bicycle safety measures may not be prioritized by local decision makers. Assessing
A34
S25
Bicyclist Acute Stress and the Road Environment
Dillon Fitch, Susan Handy University California Davis, CA, USA
Abstract Background: Bicycling is a moderate to vigorous form of physical activity, and thus has the potential to mitigate numerous chronic diseases thought to be influenced by sedentary life-styles. There is a growing consensus that promotional programs, land use planning, and restrictions on car use are important for increasing bicycling for directed travel. Nonetheless, road improvements have been one of the most strategic investment tools local and regional governments have to promote bicycling. Although there is plenty of evidence that infrastructure investments correlate with bicycling and that people prefer bicycle specific infrastructure, there still exist many questions surrounding comfort of road environments. By estimating the relationship between the road environment, perceived comfort, and psychological stress, we can improve our understanding of how to create comfortable road environments for bicycling which might encourage more people to consider bicycling as a normal mode of travel. In this paper, we present preliminary pilot results from an on-going experiment with continuous measures of bicyclist acute stress in a naturalistic bicycling task. Methods: This paper starts to fill this gap by reporting an in-depth study relating the road environment, perceived comfort, and psychophysiological measures of acute stress in college students in Davis, California. The study includes a quasi-experimental cross over (within subject) designed experiment of real world bicycling across numerous road conditions. Subject acute stress is measured physiologically through a heartbeat-to-beat measuring device (an approach often labeled heart rate variability (HRV) analysis), and subject anxiety and comfort are measured through traditional survey instruments. Results: Initial pilot data suggests a highly variable influence of the road environment on subject acute stress with individual differences in standard deviation of adjacent heart beat intervals (SDNN) ranging from 12% to 50% for low stress vs. high stress bicycling conditions. Nonlinearities were observed throughout pilot testing, and were most commonly associated with stopping at traffic signals, which showed variations in HRV in the range of 15-50%. Conclusions: Preliminary results are suggestive that HRV exhibits a psychological stress response associated with the road environment. Considerable individual differences suggest consistent group effects are unlikely to be found, and further investigation into the riding vs. approach/stop at intersections is needed. In addition, ongoing data collection will yield a larger sample of participants and warrant formal statistical analyses. http://dx.doi.org/10.1016/j.jth.2016.05.065
A35 Exposure-Based Crash Rates for Bicycle and Motorized Transport in Central Lane Metropolitan
Planning Organization Josh Roll Central Lane MPO, OR, USA
Abstract Background: Motor vehicle crashes continue to be one of the leading causes of death and disability in the United States. While population based crash rates allow for comparisons across modes and geographies to assess the burden upon the population, they do not evaluate risk. Vehicle miles traveled are typically used to normalize traffic crashes to better understand risk by allowing for exposure based rates. Similar rate calculations are rare for bicycle crash analysis due to limited bicycle traffic volume data. This work summarizes the methods used to calculate bicycle miles traveled and subsequent bike crash rates in the Eugene-Springfield, Oregon region. Methods: A facility demand model using negative binomial regression specification is used to estimate bicycle miles traveled in the EugeneSpringfield, Oregon region. These bike miles traveled estimates are then used to calculate exposure based bicycle crash rates for three injury severity levels. Bicycle crash rates are then compared to motorized vehicle crash rates using a similar exposure based rate calculation. Results: Comparison of exposure based crash rates for bicycle and motorized transport reveal significant differences with bicycle crash rates many times higher than motorized transport rates. These differences exist across all injury severity levels. Comparison of crash rates for different street designs show differences as well, intuitively revealing streets with higher vehicle speeds and higher vehicle volumes have higher crash rates for bikes and vehicles alike. Bike lanes seem to offer significant protection for people who ride bikes, though crash rates on these facilities are still higher than most facility combinations for motor vehicles. Conclusions: On average 10% of the fatal and severe injuries in the Eugene-Springfield metro area involve people riding bicycles. Due to this relatively low share of overall crash outcomes, bicycle safety measures may not be prioritized by local decision makers. Assessing