This post is a cautionary note for everyone who proposes, advocates for, or plans public transportation: please avoid numerology. What I mean by numerology is, it’s easy to target round numbers for trip time, ridership, capacity, or cost, but this may not be based on good design principles. Round numbers are memorable, which makes them attractive for marketing, but quite often the roundness percolates from public communications to system design, and then it tends to lead to bad results: excessive amounts of money spent on meeting a particular trip time, useful scope cut from a project to stay under a too tight budget, and general overpromising.
I’m tagging this incompetence because it is always bad, but even people who are generally good may unwittingly engage in numerology. I’m pretty confident I’ve done this in previous posts by accident. So I’m exhorting myself and good transit advocates and not just the usual politicians and power brokers.
10x and tech
The worst numerology that I’ve seen in technology is not specifically in transportation, but in the software industry of the American West Coast, which is obsessed with the concept of 10x, that is 10 times as good as normal. The most common variation of this is the 10x engineer, that is the programmer who gets 10 times the productivity of the average programmer, but (by implication) does not demand 10 times the average salary, or even 1.5 times the average salary.
Thanks to Elon Musk, the same concept of 10x has jumped into the transportation discourse – Musk promises a 10x reduction in construction costs for tunneling. It goes without saying he cannot deliver, but the telling thing here is the origin of the number. It does not come from some deep analysis finding that California’s tunneling costs are about 10 times as high as those of some target best practice, or even as high as those of a new method. (In fact, California is around 7 times as expensive to build in as Madrid or Seoul, the world’s cheapest cities to build in, so 10 is at the limit of plausibility.) Rather, the number came first: innovation in American tech is supposed to come in orders of magnitude, not continuous improvements, so the target was 10x, just as SpaceX’s target for space launch cost reduction is 10x even though so far the reality is maybe 1.5x or 2x.
The primary problem here is overpromising. Factor-of-10 improvements are almost nonexistent. The one example I am comfortable with in transportation is the tunneling costs in New York specifically, and even that is a problem that only emerged with the latest project, Second Avenue Subway Phase 2; Phase 1 and the 7 extension are off by a factor of 6 or 7 off the rest-of-world average (and about 15-20 off the very cheapest in the world), and East Side Access is a problem of overbuilding more than anything so I can’t even give it a specific factor. Many other things in New York are too expensive, but generally by a factor ranging from 1.5 to 3. Cutting operating costs in half, cutting rolling stock procurement costs by a third, and so on are both laudable goals, but 10x rhetoric skips them entirely. Thus comes the secondary problem with 10x-oriented numerology: just as it rounds up factor-of-7 improvements and overpromises a factor of 10, it completely ignores factor-of-2 improvements as they simply cannot plausibly be stretched to an order of magnitude.
It is common in marketing to promise round numbers for schedules: 2-hour trip times, 3-hour trip times, etc. This sometimes percolates into the planning world behind the scenes, leading to planning around discrete trip times in integer numbers of hours.
In France it’s a commonplace that high-speed rail is only competitive with air travel if the trains take 3 hours or less. The reality is very different on two levels: first, mode share is a continuous function of trip time, so the difference between (say) 2:55 and 3:05 cannot be very big. And second, in 2009, rail had a 54% mode share of all Paris-Toulon trips, on which the TGV takes 4:08-4:20, compared with 12% for air; the TGV held its own as far east as Cannes (34%), 5:26 away, and Nice (30%), 5:57 away. The 3-hour rule is alluring and may be true in one specific social class, namely airline and railway managers, but the numerology here makes it easy to stick to it even if the breakeven point keeps creeping up to 3:30, 4:00, 4:30, 5:00.
A more benign example of numerology is the 30-30-30 plan in Connecticut. Governor Lamont has proposed far-reaching investments to speed up trains to take half an hour on each of three segments: New York-Stamford, Stamford-New Haven, New Haven-Hartford. This is more or less feasible: a reasonable level of investment would reduce New York-New Haven to about 1:03 on express trains, with Stamford near the exact midpoint. However, the target trip times remain numerological: there is no obvious reason why 1:00 is so much better than 1:10. So far 30-30-30 has run into resistance from incompetent traditional railroaders, but it’s easy to imagine a future in which the governor approves the plan over their objections, and then has to decide how much money to spend on the final few minutes’ worth of speedup to meet the stated goals.
In contrast with numerology based on round numbers, there is a much more solid planning paradigm based on trip times a few minutes short of a round number. In that case, the trip time is a round number including turnaround time, which makes it easy to run trains on a clockface schedule. Differences like 1:05 vs. 0:55 are not important enough to bother passengers about, but differences in frequency between hourly and every 1:10 are critical – passengers can remember 9:05, 10:05, 11:05, 12:05 much better than they can 9:05, 10:15, 11:25, 12:35. Therefore, the integrated timed transfer plan of Switzerland and the Netherlands aims at trip times that are not very memorable, but that together with connection or turnaround time enable memorable schedules.
In addition to the tech industry’s 10x concept, more traditional cost estimations can suffer from numerology as well. Here it is important to distinguish relative from absolute costs. Relative costs are relative to an already-decided budget; in that case, it is useful to force agencies to stay within their promised costs, to discourage lowballing costs in the future (“strategic misrepresentation” in Bent Flyvbjerg’s language). Absolute costs are about numbers that sound big or small, and in that case, there is no good reason to force costs to hew to a specific number.
In the case of absolute costs, politicians may fit the program to the cost in either direction. Reportedly, the size of the stimulus bill passed by the Obama administration at the beginning of 2019 was designed to be in the hundreds of billions and avoid the dreaded trillion number, even though some of the administration’s advisors argued for $1.2-1.8 trillion. In transportation, I do not know of specific examples, but there is so much political pressure among various people who think they’re fiscally conservative that there’s bound to be pressure to go underneath a round number, in other words a political equivalent of pricing a product at $99 instead of $100.
In the other direction, visionaries may think they’re being bold by making up a high number, usually a catch round figure like $1 trillion for US-wide infrastructure. The numerology here operates on a different level from the relatively small band of just under a limit vs. just over a limit: here the main problem is that the cost figure is arbitrary, and then the list of projects to be funded is chosen to match it. If there aren’t enough good projects, agencies will either bloat the budgets of projects by lading them with semi-related spending, for example bundling a light rail line with street reconstruction and tree planting, or go forward with weak proposals that would otherwise not be funded.