An interesting observation I ran across in an interview with a Turkish journalist: Apparently, many women drivers in Turkey have begun to keep a headscarf in the car. This is just in case they run into a police checkpoint (usually for traffic purposes). In Turkey today, the police are notoriously a stronghold of religious conservatism. So when a woman drives by the police with a headscarf on, she is supposed to be less likely to be stopped for an examination of her license.
Stories like this underscore the difficulty of approaching questions like Islamic garb primarily by asking about whether covering up is a free choice. Few of our choices ever approach a liberal ideal of unconstrained considered choice. In an environment like urban Turkey today, both wearing and not wearing a headscarf are complicated options that are never as simple as an expression of faith or a fashion choice.