Paris is building a suburban Metro expansion, consisting of 200 km of which 160 are underground, carrying automated trains. This program, dubbed Grand Paris Express, is intended to provide circumferential service in the inner suburbs (on future Metro Lines 15, 16, and 18) and some additional radial service from the suburbs into Central Paris (on future Line 17 and extensions of Lines 11 and 14). The estimated cost was about €25 billion in 2012 prices – about average for a European subway. But now a bombshell has dropped: the cost estimate should be revised upward by 40%, to €35 billion for the 200 km GPX scheme and €38 billion for GPX plus related projects (such as GPX contribution to the RER E extension). You can read it in English-language media on Metro Report, but more detail is available in French-language media, such as Le Monde, and in the original report by the Cour des Comptes, the administrative court charged with auditing government finances. The goal of this post is to suggest how Ile-de-France should react to the cost overruns, using best industry practices from neighboring countries.

First, it’s worthwhile to look at the problems the Cour des Comptes report identifies. It includes a moderate amount of scope creep, on page 40, which helped raise the budget by €3.5 billion between 2013 and 2017:

• €592 million for separate maintenance facilities at Aulnay for M15 and the other lines (M14, M16, M17).
• €198 million for interoperability between two segments of M15 in the south and east; the original plan made M15 not a perfect circle but a pinch, without through-service between south and east, and building connections to permit through-running at the southeast costs extra.
• €167 million for a second railyard for storing trains on M15 East.

On page 47, there is a breakdown of the larger cost overrun accumulated in 2017, by segment. The bulk of the overrun comes from new risk assessments: whereas the budget in early 2017 was €22.4 billion plus €2.8 billion for contingency, the new cost estimate is €27.7 billion plus €7 billion for contingency. This is a combination of geological risk and management risk: the report criticizes the project for lacking enough management to oversee such a large endeavor, and recommends target costs for each segment as well as better cost control to reduce risk.

Reducing the scope of GPX to limit its cost is thankfully easy. For a while now I have puzzled over the inclusion of M18 and M17 (which the report calls M17 North, since M17 South is shared with M16 and M14 in an awkward branch). Whereas M15 is a circular line just outside city limits, serving La Defense and many other major inner-suburban nodes, and M16 is another (semi-)circular alignment to the northeast of M15, M18 is a southwestern circumferential far from any major nodes, connecting Versailles, Massy-Palaiseau, and Orly on a circuitous alignment. Between the major nodes there is very little, and much of what it does connect to is already parallel to the RER B and to one branch of the RER C, which is being replaced with an orbital tram. The suburbs served are high-income and have high car ownership, and transit dependence is unlikely, making M18 an especially weak line.

M17 North is weak as well. It is a weird line, an underground radial connecting to Charles-de-Gaulle, already served by the RER B and by the under-construction CDG Express money waste. The route is supposed to be faster than the RER B, but it is no more direct, and makes more stops – the RER B runs a nonstop train between Gare du Nord and the airport every 15 minutes off-peak. It serves hotels near Saint-Lazare better using the connection to M14, but the RER B serves these hotels, as well as the hotels near Etoile, using a wrong-way transfer at Chatelet-Les Halles with the RER A.

The Cour des Comptes report itself does not recommend pruning these two lines, but its cost-benefit calculations per line on page 29 suggest that they should be deleted. On page 30 it says outright that the cost-benefit calculation for M18 is unfavorable. But on page 29 we see that the benefit-cost ratio of M18, not counting contingency costs, is barely higher than 1, and that of M17 North is a risky 1.3. In contrast, M15 South, the section already under construction, has a benefit-cost ratio of 1.7. M15 West has a ratio of 2.3, M15 East 1.5, M14 South 2.1, and M16 about 2. The M11 eastern extension is not included on the list.

Blog supporter Diego Beghin brought up on social media that M17 and M18 are already most at risk, and local elected officials are seeking assurances from the state that these lines will not be canceled. However, given their low potential ridership, the state should cancel them over local objections. Their combined cost is €4.9 billion, or €6.3 billion with contingency, about the same as the total cost overrun since early 2017.

Instead of pouring concrete on tunnels through lightly-developed high-income southwestern suburbs and on a third express route to the airport, the region should learn from what Germany and Switzerland have had to do. Germany has higher construction costs than France, which has forced it to prioritize projects better. Swiss construction costs seem average or below average, but the entire country has only two-thirds the population of Ile-de-France, and the public’s willingness to subsidize transit as a social service is much smaller than that of the French public. Hence the Swiss slogan, electronics before concrete (and its German extension, organization before electronics before concrete).

The M18 route already has a mainline rail route paralleling it – one of the branches of the RER C. This is an awkward branch, allowing trains from Versailles to enter the core trunk from either east or west, and ridership is so low that SNCF is downgrading it to an orbital tram-train. Thus, there is no need for a new Versailles-Massy connection. Two more destinations of note, Orsay and Orly, are also not necessary. Orsay is notable for its university, but there is already a connection from the university to Massy-Palaiseau and the city via the RER B with a little bit of walking to the station, and the connection to Versailles isn’t important enough to justify building a new line. Orly is a major airport, with about 90,000 travelers per day, but most of the traffic demand there is to the city (which it will connect to via the M14 South extension), and not to Versailles. While many tourists visit Versailles, this is just one stop on their journey, and their hotels are in the city or perhaps near Eurodisney in Marne-la-Vallee.

The M17 route is a more complex situation. The only new stops are Le Mesnil-Amelot, beyond the airport, with little development; Le Bourget-Aeroport, on the wrong side of a freeway; and Triangle de Gonesse, which is farmland. All three are development sites rather than places with existing demand, and development can be built anywhere in the region. However, the new airport-city connection is interesting, as relief for the RER B.

That said, there are better ways to relieve the RER B. The RER B has trains running nonstop between the airport and the city, but only off-peak. At the peak, trains run local every six minutes, with another branch (to Mitry-Claye) also getting a train every six minutes. The trains are very crowded, with obstructed corridors and not enough standing space in the vestibules, and with 20 trains per hour on the RER B and another 12 on the RER D, delays are common. Fixing this requires some improvement in organization, and some in concrete.

The concrete (and electronics) improvement is easier to explain: the shared RER B and D tunnel is a bottleneck and should be quadrupled. With four tracks rather than two, there would be space for more RER B as well as RER D trains; 24 trains per hour on each would be easy to run, and 30 would be possible with moving-block signaling of the same kind used on the RER A. This would provide more capacity not just to the northeast, around Aulnay-sous-Bois, but also north and northwest, since the RER D could take over more branches currently used by Transilien H.

The cost of quadrupling the tunnel is hard to estimate. Local rail advocate group ADUTEC explains the problem. In 2003 a proposal was estimated to cost €700 million, but construction would disrupt service, and in 2013 a study proposed new stations platforms at Les Halles for the RER D, raising the project’s cost to €2-4 billion. ADUTEC instead proposes building one track at a time to avoid disruption without building new platforms, saying this option should be studied more seriously; the cost estimate has to be higher than €700 million (if only because of inflation), but should still not be multiple billions.

But this project, while solving the capacity problems on the RER to the north and south in the medium term, doesn’t help connect passengers to the airport. On the contrary: more RER B traffic would make it harder to fit express trains between the local trains. Already there is little speed difference between local and express trains, about four minutes with nine skipped stations. This isn’t because the trains accelerate so quickly (they don’t) or because the maximum line speed is so low (the maximum speed on the line is 110-120 km/h). Rather, it’s because otherwise the express trains would catch up with local trains, on the airport branch or on the Mitry branch.

Fortunately, the route between the approach to Gare du Nord and Aulnay-sous-Bois, where the two RER B branches diverge, has four tracks. Right now, two are used by the RER, and two by other trains, including Transilien K but also the odd intercity train. The organizational fix is then clear: the four tracks should be reassigned so that all local trains get two tracks and all express trains (including intercities and Transilien but also airport express trains) get the other two. There is very little intercity traffic on the route, which carries no TGVs, and Transilien K has only a handful of peak trains and can be folded into the RER B.

With four tracks between Gare du Nord and Aulnay, express trains could go at full speed, saving about a minute for each skipped stop. But they shouldn’t go nonstop to the airport. They should serve Aulnay, giving it fast trains to the center. Passenger boardings by time of day are available for the SNCF-owned portion of the RER and Transilien here; Aulnay is the busiest station on the RER B north of Gare du Nord, with about 20% more weekday boardings than the second busiest (Stade de France) and 25% more morning peak boardings than the second busiest (La Courneuve). If express trains stop there, then it will free more space on local trains for the stations closer in, which would permit a service plan with half local trains and half express trains, each coming every 4-5 minutes. Today the inner stations get a local train every 3 minutes, so this is a service cut, but letting express trains handle demand from Aulnay out, on the airport branch as well as the Mitry and Transilien K branch, would mean passengers wouldn’t clog the local trains as much.

Potentially this could also reduce the demand for M16, whose northern segment, currently planned to be interlined with M14 and M17, is radial rather than circumferential. The entire M16 has a high benefit-cost ratio, but this could change in the presence of more RER B and D capacity. It may even be prudent to consider canceling M15 East and rerouting the remainder of M16 to complete the circle, a Line 15 consisting of the segments planned as M15 South, M15 West, and M16.

The study shows there is demand for two circumferentials in the east and northeast (M15 East and M16), but if RER B improvements rob M16 of its usefulness as a radial then this may change. If RER B improvements reduce the benefit-cost ratio of M16 below 1.5, then it should be canceled as well; with a budget of €4.4 billion plus another €1.2 billion in contingency, M16 could fund radial improvements that are more useful elsewhere. M15 East is a more coherent circumferential, with connections to Metro lines, whereas M16 is too far out.

But despite lack of coherence, M16 serves key destinations on the RER B. By default, the plan for GPX should be canceling M17 North and M18, and instead quadrupling the RER B and D tunnel and running more north-south RER service. Further cost overruns should be limited by the mechanisms the Cour des Comptes proposes, including tighter oversight of the project; without M17, there also may be room for removing ancillary scope, such as the Aulnay railyard.