Although Bangkok's canals historically served as a major mode of transport, they have long since been surpassed in importance by land traffic. Charoen Krung Road, the first to be built by Western techniques, was completed in 1864. Since then, the road network has vastly expanded to accommodate the sprawling city. A complex elevated expressway network helps bring traffic into and out of the city centre, but Bangkok's rapid growth has put a large strain on infrastructure, and traffic jams have plagued the city since the 1990s. Although rail transport was introduced in 1893 and trams served the city from 1888 to 1968, it was only in 1999 that Bangkok's first rapid transit system began operation. Older public transport systems include an extensive bus network and boat services which still operate on the Chao Phraya and two canals. Taxis appear in the form of cars, motorcycles, and "''tuk-tuk''" auto rickshaws.