Nils Wilcke
@paul_denton@mastodon.social  ·  activity timestamp 2 weeks ago

La SNCF pourrait choisir Starlink, le vaste réseau de Musk, pour équiper ses trains de la technologie satellite face à son rival européen Eutelsat. En septembre dernier, SpaceX a déjà été sélectionné par Air France-KLM pour installer progressivement le wifi à bord de tous ses avions. Confier nos moyens de communication dans les transports à un milliardaire fascisant, une riche idée! https://www.lalettre.fr/fr/entreprises_tech-et-telecoms/2025/07/03/le-plan-d-elon-musk-pour-brancher-les-tgv-francais-sur-starlink,110472501-eve

#Politique#SNCF#Transport#Musk#Starlink#Avion#Train#TGV#Satellite

Paul
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Jon Sullivan
@joncounts@mastodon.nz  ·  activity timestamp 2 weeks ago

The new science video from #Veritasium is wild and worth a watch.

It's about Braess’s Paradox, which I'd not heard of before, but it shows up in all sorts of places, including traffic planning.

The video includes a fantastic couple of examples of why car traffic times can sometimes go up when more roads are built. That's not the usual case of more people using the roads. Instead, with the same number of drivers, adding a road makes everyone's journey time slower.

This example might seem a bit contrived but the video also cites a study where the equivalent did happen when a busy street in New York City was closed off, and travel times for everyone paradoxically went down.

Physics and maths are wonderfully counterintuitive sometimes.

https://www.youtube.com/watch?v=-QTkPfq7w1A

#physics#SciComm #transport #traffic

In this modified road layout, the city has built a short 1 minute section of motorway connecting the two city street sections of route together. The shortest travel distance is now going straight down the midde, but since everyone chooses to take that route, the city street sections become slower and travel time *increases* from 35 minutes to 41 minutes. If a car chose to take one of the side routes it would take even longer (45 minutes) as they would end up on a clogged city street with everyone else. (Do watch the video for a much clearer explanation.) Screenshot from https://www.youtube.com/watch?v=-QTkPfq7w1A
In this modified road layout, the city has built a short 1 minute section of motorway connecting the two city street sections of route together. The shortest travel distance is now going straight down the midde, but since everyone chooses to take that route, the city street sections become slower and travel time *increases* from 35 minutes to 41 minutes. If a car chose to take one of the side routes it would take even longer (45 minutes) as they would end up on a clogged city street with everyone else. (Do watch the video for a much clearer explanation.) Screenshot from https://www.youtube.com/watch?v=-QTkPfq7w1A
In this modified road layout, the city has built a short 1 minute section of motorway connecting the two city street sections of route together. The shortest travel distance is now going straight down the midde, but since everyone chooses to take that route, the city street sections become slower and travel time *increases* from 35 minutes to 41 minutes. If a car chose to take one of the side routes it would take even longer (45 minutes) as they would end up on a clogged city street with everyone else. (Do watch the video for a much clearer explanation.) Screenshot from https://www.youtube.com/watch?v=-QTkPfq7w1A
A diagram showing two road routes from start to end. Each route contains two sections. One section is wide motorway where travel time is always 25 minutes and not related to the number of cars (within the volumes of this example). The other section is a narrow city street where travel time *is* proportional to the number of cars (one extra minute for each 100 cars). In this example, if there are 2000 cars, and half take each route, then the journey time is 25 minutes + 10 minutes = 35 minutes. This is a screenshot from https://www.youtube.com/watch?v=-QTkPfq7w1A
A diagram showing two road routes from start to end. Each route contains two sections. One section is wide motorway where travel time is always 25 minutes and not related to the number of cars (within the volumes of this example). The other section is a narrow city street where travel time *is* proportional to the number of cars (one extra minute for each 100 cars). In this example, if there are 2000 cars, and half take each route, then the journey time is 25 minutes + 10 minutes = 35 minutes. This is a screenshot from https://www.youtube.com/watch?v=-QTkPfq7w1A
A diagram showing two road routes from start to end. Each route contains two sections. One section is wide motorway where travel time is always 25 minutes and not related to the number of cars (within the volumes of this example). The other section is a narrow city street where travel time *is* proportional to the number of cars (one extra minute for each 100 cars). In this example, if there are 2000 cars, and half take each route, then the journey time is 25 minutes + 10 minutes = 35 minutes. This is a screenshot from https://www.youtube.com/watch?v=-QTkPfq7w1A