Proof-of-payment with ungated train stations is a useful technique for reducing construction costs. It simplifies the construction of stations, since there is no need for a headhouse or mezzanine – people can go directly from the street to the platform. A station without fare control requires just a single elevator, or two if side platforms are desired, and can be built shallowly using cut-and-cover. Cities across the size spectrum, perhaps only stopping short of hypercities, should take heed and use this to build urban rail more cheaply.
Is this a common cost control technique?
No. The vast majority of low-construction cost countries use faregates, which is why I was reticent to recommend proof-of-payment as a cost mitigation strategy. Spain, Italy, Korea, and Sweden are all faregated; among the world’s lowest-cost countries, I believe only Finland and Switzerland use proof-of-payment fare collection on urban rail.
However, there are exceptions. In Italy, the Brescia Metro uses proof-of-payment. This is not typical for the country or the region – Italian metros have fare control, like the vast majority of systems outside Germany and Germany-influenced countries. However, because Brescia is small, the system was forced to engage in value engineering, removing scope that would be routine in larger cities like Milan. The majority was built cut-and-cover or above-ground; the typical urban Italian metro is entirely bored. Italian metro systems prefer short stations on new lines to minimize costs and provide capacity through automated operations and extremely high frequency; Brescia takes this to an extreme and has 30-meter trains. Among these cost minimization tactics is the lack of fare control. The result of this entire package is that Brescia spent 915 million euros on a 13.7 km metro system.
Station size and station cost
So far, we believe that the cost of the station, excavation excluded, should be proportional to the floor area. This is based on something told to us in an interview about electrical system costs for the Boston Green Line Extension, which is light rail in a trench rather than a tunneled metro system, so I recommend caution before people repeat this uncritically.
Moreover, on somewhat more evidence, it appears that the cost of station excavation should be proportional to the volume excavated. Some of the evidence for this is circumstantial: media reports and government reports on the construction of such urban rail projects as Second Avenue Subway, Grand Paris Express, and the RER specify the volume of excavation as a measure of the difficulty of construction. But it’s not just circumstantial. In Paris, the depth of some of the GPX stations has led to some construction complications. Moreover, preliminary interviews in Paris suggest, albeit not definitively, that station construction costs are predominantly a matter of dig volume. Finally, the insistence on short platforms and high frequency as a cost saving technique on new-build metro systems in Italy as well as in Denmark and on the Canada Line in Vancouver is suggestive too, even if it says nothing about whether the relationship between volume and cost is linear, degressive, or superlinear.
How does one minimize station costs with POP?
Proof-of-payment means that there is no fare control between the street and the station. This means any of the following ways of constructing station access become available:
- Cut-and-cover with the platform on level -1, with direct stair and elevator access from the street. The Berlin U-Bahn is built this way, with access points in street medians where available, such as U8 on Brunnenstrasse. It’s easy to build staircases at each end of the platform to increase access, with an elevator in the middle.
- Bored tunnel with large enough bores to fit the platform within the bore. The Barcelona method for this is to use 12-meter bores, but smaller, cheaper versions exist with smaller trains, for example in Milan. It’s also possible to use double-O-tube TBMs for this, but ordinarily they are more expensive than twin bores. Access involves vertical bores down to the platform with elevators or slant bores with escalators; there is no need for intermediate levels or entry halls.
- Bored tunnel with cut-and-cover stations, with no mezzanine levels. Here, the dig volume is unchanged, and the saving from lack of fare control is only in the finishes and elevator costs, not the excavation.
It is noteworthy that the most common technique for metro construction, by far, is the last one, where the savings from POP are the smallest. The vast majority of world metros have fare control, including in low-cost countries, and this perhaps makes metro builders not notice how two separate ways of reducing costs – cut-and-cover and POP – interact especially well together. Nonetheless, this is a real saving.
What does this mean?
A technique can be uncommon in low-cost countries and yet be useful in reducing construction costs. It is useful to think of the way Madrid, Milan, Turin, Stockholm, Oslo, Helsinki, and Seoul build their urban rail systems as good, but not always perfect. A trick that these cities might not pay attention to may still be good. The caveat is that it requires a good explanation for why they have not employed it; in the case of Italy, I believe it’s simply that the non-German world views fare control as the appropriate way to run a metro system and POP as a light rail technique and therefore only good for low-volume operations. There may also be backward compatibility issues – Brescia is a new build, like POP Copenhagen, whereas Milan is building extensions on top of a gated system.
Nonetheless, the evidence from station costs, the success of POP operations in Germany even on very busy lines, and the experience of Brescia all suggest that POP is good for metro construction in general. Cities smaller than New York building new systems should use it exclusively, and cities that already have faregates should tear them down to improve passenger circulation and facilitate the construction of POP lines in the future at lower cost.