The public bus system is quite well-developed in Abu Dhabi. Blue and white coloured buses run through the city regularly and tickets are available in the form of re-loadable "Halifat" Smartcards, that may be purchased from ticket vending machines located at multiple locations throughout the city (bus stations and stops, DOT Customer Service Centers). Hold your card next to a card reader installed inside the bus for validation upon entry and exit. A ferry service is provided by DOT: on many ferries you will be asked to show a valid ID and, in general, it is recommended to arrive 30 minutes before the ferries' departure. Another good way to travel around the city and avoid the congestion is by using the Abu Dhabi Metro, which serves a big proportion of passengers and connects the city with its suburbs.