Tag: transit

City Microbiomes

Researchers took 4700 samples from mass transit systems in 60 cities across the world, swabbing common touch points like turnstiles and railings in bustling subways and bus stations across the world. Using metagenomic sequencing, they created a global atlas of the urban microbial ecosystem, the first systematic catalog of its kind. The results suggest that no 2 cities are alike, with each major metropolis studied so far revealing a unique molecular echo of the microbial species that inhabit it, distinct from populations found in other urban environments.

2023-10-12: Dark matter

Metagenomes encode an enormous diversity of proteins, reflecting a multiplicity of functions and activities. Exploration of this vast sequence space has been limited to a comparative analysis against reference microbial genomes and protein families derived from those genomes. Here, to examine the scale of yet untapped functional diversity beyond what is currently possible through the lens of reference genomes, we develop a computational approach to generate reference-free protein families from the sequence space in metagenomes. We analyse 27k metagenomes and identify 1.17b protein sequences longer than 35 amino acids with no similarity to any sequences from reference genomes. Using massively parallel graph-based clustering, we group these proteins into 106k novel sequence clusters with more than 100 members, doubling the number of protein families obtained from the reference genomes clustered using the same approach. We annotate these families on the basis of their taxonomic, habitat, geographical and gene neighbourhood distributions and, where sufficient sequence diversity is available, predict protein three-dimensional models, revealing novel structures. Overall, our results uncover an enormously diverse functional space, highlighting the importance of further exploring the microbial functional dark matter.

MTA could 2x off-peak capacity for free

In New York, the frequency of a bus or subway service is regularly adjusted every 3 months to fine-tune crowding. Where Berlin has a fixed clockface timetable in which most trains run every 5 minutes all day, New York prefers to make small changes to the frequency of each service throughout the day based on crowding. The New York approach looks more efficient on paper, but is in fact the opposite. It leads to irregular frequencies whenever trains share tracks with other trains, and weakens the system by leading to long waits. But another problem that I learned about recently is that it is unusually inconvenient for labor, and makes the timetabling of trains too difficult. New York should timetable its trains differently. Berlin offers a good paradigm, but is not the only one. As far as reasonably practical, frequency should be on a fixed clockface timetable all day. This cannot be exactly 5 minutes in New York, because it needs more capacity at rush hour, but it should aim to run a fixed peak timetable and match off-peak service to peak service. It’s a large increase in service. Frequency-ridership spirals work in your favor here. Increases in service require small increases in expenditure, even assuming variable costs rise proportionately – but they in fact do not, since regularizing frequency around a consistent number and reducing the peak-to-base ratio make it possible to extract far more hours out of each train driver, as in Berlin. Net of the increase in revenue coming from better service, such a system is unlikely to cost more in public expenditure.

This remains true even assuming no pay cuts for drivers in exchange for better work conditions. Pay cuts are unlikely anyway, but improving the work conditions for workers, especially junior workers, does make it easy to hire more people as necessary. The greater efficiency of workers under consistent timetabling without constant fidgeting doesn’t translate to lower pay, but to much more service, in effect taking those 550 annual hours and turning them into 900 through much higher off-peak frequency. It may well reduce public expenditure: more service and thus greater revenue from passengers on the same labor force.

they’d have to stop constantly messing with the schedule, which is pure insanity.

Electronics before concrete

The secret why swiss transit works so well: the whole schedule is synchronized:

Systemwide optimization invariably shows seams in the system. When Switzerland designed the Bahn 2000 network, there was extensive optimization of everything, but at the end of the day, Zurich-Bern was going to be more than an hour, which would not fit any hourly clockface schedule. Thus the Mattstetten-Rohrist line was born, not out of desire to run trains as fast as possible, but because it was necessary for the trains to run at 200 km/h most of the way between Olten and Bern to fit in an hourly takt.

The same is true of speed and capacity improvements. A faster, more reliable system attracts more passengers, and soon enough, a line designed around a train every 15 minutes fills up and requires a train every 10 minutes, 7.5 minutes, 6 minutes, 5 minutes, 4 minutes. An optimized system that minimizes the need for urban tunneling soon generates so much ridership that the tunnels it aimed to avoid become valuable additions to the network.

US Transit growth

This growth was driven almost entirely by an influx of subway, commuter rail, and bus trips in the New York City region, as well as subway trips on Washington, D.C.’s Metro. Both cities, which have the nation’s 1st- and 3rd-highest shares of transit commuters, have weathered major reliability and maintenance crises in recent years and hemorrhaged riders as a result.

Rolling Stock Costs

Despite this conservatism, costs are very high, consistent with a factor somewhat higher than 2 on commuter rail and somewhat lower than 2 on the subway. But perhaps the conservatism is what increases costs in the first place? Perhaps the reason costs are high is that the world market has moved on and the MTA and some other American operators have not noticed. In Chicago, Metra found itself trying to order a type of gallery car that nobody makes any longer, using parts that are no longer available. Perhaps the same kind of outmoded thinking is present at the MTA, and this is why costs have exploded in the last 10 years.

Scooters

At least at eye level, the lax regulations France does have – the minimum age is 8, cities may choose to permit or prohibit riding on the sidewalk, riding on all streets with speed limit up to 50 km/h is required – appear sufficient. The American, British, and Italian approaches are too draconian and only serve to discourage this mode of transportation.