In the Paris region, more and more workers have working hours that are no longer explicitly fixed by the employer. Instead, they have what we call flexible working hours. According to theories in transport economics, this greater freedom given to employees should spread out people’s starting hours and therefore contribute to improving travel conditions at rush hour. But is this actually the case? Are more flexible working hours really the right solution to end the problems of rush hour congestion? Do employees with flexible schedules actually avoid the morning rush hour? And more generally, how do they choose to set their own working hours?