MONITORING PLACES OF DETENTION : A PRACTICAL GUIDE ■ 70 the travelling time between different places of detention. 2.4 Frequency of the visits Experience shows that visits will be much more effective in terms of the prevention of torture or ill-treatment, and promoting sustained improvement, if they take place regularly. How often a place of detention will need to be visited depends on several factors. The frequency of the visits can be determined according to: ■ the type of place of detention; ■ pre-trial detention facilities such as police stations should generally be visited more frequently than penal establishments because: - interrogations are held there; - detainees’ contacts with the outside world are limited; - there is a rapid turnover of detainees; ■ the risks – known or presumed – to which persons deprived of their liberty are exposed, or any protectionrelated problems noted; ■ the balance to be struck, over time, between the needs of the visiting body and the needs of the officials in charge in order to carry out their work. Frequently repeated routine visits can, in the long run, be counterproductive if they disrupt the work of the staff without valid reason. The frequency of visits also largely depends on the gravity of the protection problems encountered. In cases where the visiting