DETAILED planning has started for a fourth metro line in Milano. The 15 km route running from the southwest to the east of the city will serve a heavily-used bus corridor and relieve pressure on the parallel Line 1 between Cadorna and Pagano-Bisceglie. It will be totally underground.

Metropolitana Milanese is due to complete the final design by the end of 1999, following the approval of a feasibility study late last year. MM will also examine the various options for private sector financing, with the aim of starting construction in 2000-01.

Line 4 will link Lorenteggio with Linate airport, serving 20 stations. There will be interchanges with Line 2 at Porta Genova, Line 3 at Crocetta and with Line 1 at Piazza San Babila via an underground travolator. A connection is also planned to the Passante cross-city railway at Dateo. Line 4 will serve the city centre and key traffic points such as the Statale University, the Policlinico Hospital and the Law Courts.

MM envisages building the line to light metro standards, with a target capacity of 10000 passengers/h in each direction. A smaller tunnel cross section and stations with 70m platforms will cut construction costs, as will shallow stations offering direct access to the platforms without a mezzanine level. Rolling stock will be derived from the latest light rail vehicles, and studies are under way to determine the level of automation.

Total cost is put at 1bn euros, including the rolling stock and depot facilities. Construction is expected to take six years, but MM is looking at the scope for developing the line in two or three phases to match the availability of funding.

Key facts

n Line 4 to be light metro, with LRV derived cars

n 15 km east-west route, all underground

n Private funding envisaged