MOST cities build their metro networks in stages and find building one or two lines a sufficient challenge, so it was rather surprising when Riyadh announced a bold plan to build six lines totalling 176.6km simultaneously in just five years, in a country which has only built one metro line so far, in Mecca, and which lacks sufficient expertise to take on the task itself. Nevertheless, this is the challenge which ArRiyadh Development Authority (ADA) has set itself, and it is indicative of the huge infrastructure projects which Saudi Arabia has already embarked upon, such as the North-South railway nearing completion and the Haramain high-speed line under construction in the west.

There is no doubt about the necessity to build a metro in the Saudi capital. The current population of 5.7 million is forecast to grow by 40% to reach 8.3 million by 2030 while transport demand is expected to rise even more rapidly with a 60% increase predicted over the same period.

"Road traffic is terrible, with a lot of bottlenecks, and it is a very difficult city to drive in," says Mr Wadii Bouchiha, Middle East commercial director with Systra, a member of a consortium led by Parsons and including Egis Rail which has been appointed under a €425m contract to manage the project and supervise construction for lines 1, 2 and 3. "With more than 5 million inhabitants, and 7.4 million car trips a day, Riyadh needs an alternative to cars, so the city has developed a long-term vision. The metro is one component, but Riyadh also wants to develop and expand its bus network and the city launched a tender in 2013 to have new buses running on new routes with a new operator."

In order to make the metro project more manageable, it has been split into three design-build contracts, known as packages. "All six lines will be built to the same standards, and all contractors must comply with them," Bouchiha explains. "It will be a relatively small-scale metro with 60m-long platforms. Riyadh is looking to accommodate between 15,000 and 20,000 passengers/ hour/direction depending on the line in the medium term."

Headways of 90 seconds are planned using communications-based train control (CBTC) with driverless operation and platform-screen doors at stations. "Trains will be between 2.7 and 2.8m wide but it is up to the contractor to decide train length," says Bouchiha. "About 30% of the design work was completed at the bidding stage, and detailed design is being done as part of the contract. We wanted the contractors to complete final design within 14-15 months, but we will have to wait for them to organise themselves. As long as they complete the project within the overall timetable it is up to them when they complete final design."

ADA announced the winners of the three design and build contracts, worth a total of $US 22.5bn, in July last year. Lines 1 and 2 (package 1) will be designed and built under a $US 9.45bn contract awarded to the Bacs consortium led by US engineering giant Bechtel, and including Aecom and Siemens. The Arriyadh New Mobility Group, led by Ansaldo STS and including Bombardier which will supply the trains, won a $US 5.2bn contract for Line 3 (package 2), while a $US 7.8bn contract for lines 4, 5 and 6 (package 3) was awarded to the Fast consortium led by FCC, Spain, and including Alstom, Samsung C&T, Strukton, Setect, France and Typsa, Spain.

RiyadhThe metro will have 87 stations of which seven will be interchanges between lines. There will also be an interchange with a light metro serving Princess Noura Bint Abdul Rahman University, a new 3.6km automated monorail which will serve the huge King Abdullah Financial District development currently under construction, and a connection with mainline trains at Riyadh station. Around 42% of the network will be underground, 47% elevated and the remaining 11% at grade. Lines 4 and 6 will share the same tracks between Al-Iman Muhammad bin Saud Islamic University and King Abdullah Financial District. Despite the scale of construction, contractors must avoid disrupting normal city life wherever possible.

Apart from the common section of lines 4 and 6, the lines will be largely separate from one another, and Alstom, Bombardier, and Siemens are each providing their own design of train, so several maintenance workshops, depots and train stabling and cleaning areas will be needed. Package 1 will have one heavy-maintenance workshop, one depot and two train stabling areas, while package 2 will have three combined depot/overhaul/train stabling facilities.

Alstom will supply a fleet of 69 two-car Metropolis trains for operation on lines 4, 5 and 6. Alstom will also equip the three lines with CBTC, its Hesop energy recovery system, and will use its Appitrack system for tracklaying.

Bombardier will build 47 two-car Innovia Metro 300 trains at its plant in Sahagún, Mexico, and plans to send the first trains to its test facility in Kingston, Canada. The trains will be equipped with Bombardier's Mitrac propulsion system and full-width gangways. They will operate on Line 3, a 40.7km east-west line serving the southern part of Riyadh.

Siemens has a turnkey contract worth around €1bn to supply 74 trains for lines 1 and 2, which will total 63km. It will install CBTC, 31 electronic interlockings and the control centre for the two lines, as well as being responsible for electrification. The aluminium-bodied trains will be based on Siemens' Inspiro design but will have a different car-body shape to meet the wishes of the client. The trains, which will be formed into two and four-car sets, will have high-capacity air-conditioning to supply sufficient cooling power to ensure the wellbeing of passengers even in extreme heat. The bogies, traction drive, brakes and doors will be fitted with special seals and filters to reduce the ingress of sand.

"It has not been decided how to operate the metro yet," Bouchiha reveals. "However, there will be one operating control centre for the entire network with each line controlled separately from one location. There will also be a transport control centre covering the metro, buses, intelligent transport systems, and the road network."

Riyadh does not simply want a functional metro, but one which is iconic and fit for the 21st century. To that end, international architects have been engaged to design three of the most important interchanges which will become landmarks in their own right and powerful symbols for the new metro.

Dubai metro already offers two classes of travel on its trains, but Riyadh plans to go one better by offering three, namely first class, family class to cater for mothers and children, and standard class. It will be interesting to see how the operators manage this on relatively short trains on what could become a busy metro.

Another challenge for a project of this size is recruiting and mobilising sufficient people to design, supervise and implement it. "For packages 1 and 2, we will need 900 to 1000 people for project and construction management at the peak of the project," Bouchiha explains. "The design review team to approve the final design and the construction supervision team will account for a large proportion of the people we need.

"As we require people with railway knowledge and project management skills, the market in Saudi Arabia does not have all the resources we need so we will have to look elsewhere initially. One of our commitments is to develop knowhow locally by working with universities. Companies are required to have a proportion of Saudi employees, with the exact number related to the size of the company. But we want to go further than this, as we want to share knowledge with Saudis."

It is hoped that the first construction work will commence soon, with a view to opening the first completed sections in 2018 and completing the entire project by the following year. There is no doubt contractors will be under huge pressure to complete such a large project within this demanding timescale.