Psychology / California / Humans / Walking / Darkness / Circadian Rhythm / Risk factors / Accident analysis and prevention / Public health systems and services research / Urban Population / Risk Factors / Seasons / Wounds and Injuries / Cross Sectional Studies / Circadian Rhythm / Risk factors / Accident analysis and prevention / Public health systems and services research / Urban Population / Risk Factors / Seasons / Wounds and Injuries / Cross Sectional Studies