It's an almost universally accepted truth that walking in well-lit areas is safer. But Aaron Chalfin, associate professor of criminology in Penn's School of Arts & Sciences; John MacDonald, criminology professor and director of the Master of Science in Criminology, and Brian Wade, senior data scientist at Penn's Crime and Justice Policy Lab, want to know what this knowledge means on a society level: Could improving vast swaths of a city's lighting enhance public safety by acting as a significant deterrent to crime?