UNVEILED in 2007 by the then French president Mr Nicholas Sarkozy, the Grand Paris initiative is a masterplan for the urban development of the greater Paris area. The project aims to reinvigorate the city's suburbs by linking them with a new public transport system, encouraging the development of new economic hubs and the construction of up to 70,000 sustainable new homes each year, all the while contributing to modal shift. At the heart of Grand Paris is an ambitious plan for a 160km automatic fast metro network that will link the city's suburbs and connect the Paris region with the city's two main airports, Orly and Roissy Charles de Gaulle, as well as peripheral high-speed rail stations.

In June 2010 the French government passed the Grand Paris Act, which created Société du Grand Paris (SGP), a state-owned organisation whose purpose is to design and build the metro network by 2025. SGP also has a remit to develop commercial and residential property on land around future stations, which will generate revenue to help fund the project.

"This is certainly an ambitious project, but it is a consequence of underinvestment in the transport network since the construction of the RER network," says SGP director Mr Didier Bense. "Suburb-to-suburb journeys have increased in recent decades but there has been no public transport response to this change. It's time to fill in the gaps and catch up. This is about the competitiveness of the Paris region, access to jobs, and sustainable living."

The network will comprise three lines. The Blue Line will run through the heart of Paris, linking St Denis Pleyel in the north with Orly Airport in the south. The 9km central section of the line between St Lazare and Olympiades will utilise the infrastructure of the existing Line 14, Paris's first automatic metro line, which opened in 1998. Between St Lazare and Mairie de St Ouen the Blue Line will also take over part of metro Line 13, relieving one of the busiest sections of the metro network. Bense says a key priority in this project will be to minimise disruption to the existing line, which carries around 450,000 passengers per day.

The 28km Blue Line will retain the rubber-tyred system used on Line 14, although SGP is currently studying whether the existing signalling system on this line should be replaced with the latest CBTC technology to ensure maximum reliability and minimise the risk of obsolescence. By 2035 the line is expected to carry 38,000 passengers per hour per direction (pphpd), with 120m-long trains accommodating 960 passengers, and a minimum headway of 85 seconds. A commercial speed of 45km/h is envisaged, with a 37-minute journey time between Orly and Pleyel. The €1.2bn northern extension is due to be completed by 2018, while the €2bn Orly extension is expected to open by 2020.

Preliminary design is nearing completion on the 95km Red Line, a circle line that will connect Nanterre with Champigny, Le Bourget, St Denis Pleyel, and La Défense, with a branch serving Le Bourget and Roissy Charles de Gaulle airports before terminating at Le Mesnil-Amelot.

Red Line trains will operate at minimum headways of 120 seconds on the busiest sections during the morning peak. Steel-wheel trains will be used with a width of 2.8m and capacity for at least 1000 passengers per train. Demand is expected to be highest around La Défense, at 30,000pphpd, while the line to Charles de Gaulle will be the lowest density, at around 10,000pphpd.

A public inquiry will begin later this year, which is expected to take around seven months to complete. Tenders will be launched in the middle of next year and full construction will begin in early 2014, initially on the section to the south of the city, which will open in 2018. The remainder of the line will open in phases by 2025.

The line, which will have 40 stations, is likely to become the world's fastest driverless metro, with a commercial speed of 60km/h and a maximum operating speed of 120km/h. This should allow trains to complete a full circuit of the line in 93 minutes. "More than 15% of Red Line passengers will be car users," says Bense. "If you want to attract people who drive, speed is essential for longer distance trips."

Construction of the Red Line will also relieve some of the most congested parts of the metro network, reducing ridership on all existing metro lines by 10-15% and providing more capacity for journeys into the city centre. It will relieve pressure on major interchanges like Châtalet, where many passengers making suburb-to-suburb journeys currently change trains.

According to Bense, the €2.3bn Green Line from Orly to St Quentin and Versailles Chantiers on the southwestern side of Paris will open up a large area which currently has poor access to the rail network. This is a low density route with projected ridership of around 6000pphpd, and around 40% of the 35km line will be on viaduct. The 15km section from Versailles to an interchange with the Red Line and a planned TGV station at Nanterre has been deferred until after 2025.

SGP will oversee the design and construction of all three lines, and will be the owner of the infrastructure and rolling stock, taking responsibility for all construction debt over a 40-year period. Ile de France Transport Authority (Stif) will specify the service level and appoint an operator by international tender in 2015-16, which in turn will pay a usage fee to SGP for operating the network. Paris Transport Authority (RATP) will maintain the infrastructure.

The total investment in the Red, Blue and Green lines is €17.5bn at 2008 prices. The French government will allocate €4bn to the project, while €1.5bn will come from local government and €7bn from loans, which will be secured from 2016 onwards, with the remainder being generated through local commercial and property taxes.

Orange Line

A further project being managed by Stif is the €3.7bn Orange Line. The 29km east-west line will connect Noisy-Champs and Champigny Centre with St Denis Pleyel, with a second phase extending the line to Nanterre. The 16-station line will serve an area with a high density of suburb-to-suburb traffic, and is expected to reduce St Denis Pleyel - Bobigny-Picasso journey times by 15 minutes, and Créteil - Rosny-Bois-Perrier by 40 minutes.

A public inquiry is scheduled to begin at the end of next year. A decision has yet to be made on what technology will be used, although SGP says rolling stock could be compatible with the Red Line.

Bense stresses that the automated metro is not being built at the expense of other transport infrastructure, and is part of a broader strategy, which includes a further €12bn investment in the city's RER, metro, tram, and bus networks by 2025.