Santiago Metro, Chile
The Chilean capital city of Santiago has a large, and still expanding, metro system, which, unusually, uses rubber-tyred vehicles.
The system serves a metropolitan area with a population of 4.6 million, which represents almost a third of the country's entire population.
A plan drawn up in 1968 envisaged the construction of five metro lines, using rubber-tyred vehicles, and extending to a total of 60km (40 miles). Constructon work began in 1969, with the first line opening to the public in 1975, followed three years later by the first section of Line two.
As of 1998, the system operates on five routes and has 52 stations, with a total system length of 40.4km. It runs on 1,435mm gauge track and there is a widespread network of feeder buses from five key stations, which serve 20 different routes.
The network employs differential (high, medium and low level) fares, according to the day and time of travel. Through tickets are also available to some stations on the suburban heavy rail network.
Peak-hour services run at frequencies of every three minutes, while off-peak train intervals vary from three and a half to eight minutes.
In 1996, the two existing lines of the metro system carried 178 million passengers, a very high figure in relation to the city's population, indicating its popularity.
However, that still represents only 8.2% of the total transport journeys into and through the city. Early estimates suggested that the planned third route could carry up to 800,000 passengers per day.
The third line (Line 5) opened in 1997. It was planned as a result of the success of the earlier routes, but this was to be unusual in including the system's first stretch of elevated track.
Indeed, the majority of this 10.5km route - 6km - is being constructed in this way, while 3km - from Baquedano to Irarrazaval and Bellavista, including running under Bustamente Park - are to be built underground, with the final 1km consisting of street running.
A 2.8km extension to line 2, from Baquedano to Bellas Artes and Plaza de Armas, has been completed with three stations. It opened in February 2000.
The new Lines 4 and 4A will follow a tangential alignment to cover the urban districts to the southeast and, like the existing lines, will run partly in tunnels. Over a total distance of more than 30km, it will stop at 28 stations, one of them serving as interchange station to Line 1.
The trackbed on which the rubber-tyred vehicles operate is of standard concrete, with the rails constructed of relatively light 40kg/m guide rails.
The first two lines of the network form a 'T' shape. Line one runs east to west, linking E. Militar and San Pablo, with line two being a north-south route, from Cal Y Canto to Lo Ovalle. The two lines intersect at Los Heroes, just east of the city centre.
Line 5 again runs north to south, this time leaving Line 1 at Baquedano, east of the existing junction with Line 2, and heading south to a terminus at Americo Vespucio.
The stations on the new route are perhaps its most distinctive feature, with several elevated stations being housed in futuristic tube-like shells, to afford protection from all weathers.
All 12 of these stations will be fully accessible to disabled users, after the operators studied closely modern practice on other systems across the world.
250 vehicles were built by Alsthom-Atlantique between 1975 and 1980 for the first generation of services.
The operators get an amazing level of usage from the vehicles, as 49 sets of between four and six vehicles are expected to be in traffic every day during peak hours.
The next generation of rolling stock is also to come from Alstom (as it is now known).
This will comprise 58 new vehicles, some for use on the new line five. This new rolling stock is based closely on an order built by the same company for the Paris Metro, France, and is being constructed in that country, at the CIMT works in Valenciennes.
12 of the new sets will be used to increase capacity on Lines 1 and 2, while another batch of 12 six-car sets, designated NS93 and based on the 1989 build of stock for the Paris Metro by the same manufacturer, is on order.
SIGNALLING / COMMUNICATIONS
The line five construction project also included renewal of signalling on the existing routes, at a cost of $40 million. Renewal of the automatic train control system was carried out by CMW Equipamentos of Brazil, while the corresponding train equipment was supplied by French firm Systra.
By 1997, when the first trains on Line 5 began operation, the Santiago Metro carried 199.7 million passengers, an increase of more than 30 million in two years.
More than half of this figure was accounted for by journeys on the new Line 5, and while ridership on Line 1 was continuing on an upward trend - up by more than 10% - there was a fall of almost a third in the number of passengers travelling on line 2. This can perhaps be accounted for by the proximity of the new Line 5, and its almost parallel routing.
The Chilean government's continued commitment to reducing road congestion means that extensions to the network are still being looked at.
The next project is Line 4A, which is the first to receive steel-wheeled trains. Planning work started in 2002, and includes a new 8km-long viaduct. By 2015, there should also be two more completely new routes (lines 3 and 6).