The mathematics of speeding | Hacker News Reader

The mathematics of speeding

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13 pointscovfiefy7 comments

On straight drive road trips from Washington State to California in my late teens to early twenty’s, driving 80 vs 60 had a huge effect in my mind. 16 hours at 60mph vs 12hrs at 80mph seemed like a lot. Even counting the half hour I lost getting a ticket I got going 80 in a 60 in weed, , I swear to this day I still see lots of speed traps there.

Where as a 12 minute drive around my hometown didn’t mean much to me compared to a 16 minute one.

Maybe that’s because I’m one of those people who has a hard time counting how I spend my minutes in a day, and I generally count in hours.

Though now that I’m older the idea of a road trip to California taking several days sounds more appealing than speeding through the night. Though maybe that’s because I’m no longer working my highschool $6.50/hour job, and stopping lots for food and hotels doesn’t sound like going broke.

Now consider that kinetic energy increases with the square of velocity.

Going from 60mph to 80mph may save some time on a really long road trip but increases the energy you'll feel in a crash by 77%

Good point, though not as if my 20 something self would’ve thought of that. I would go like 125mph on the 520 floating bridge on my motorcycle, because.... I have no idea. :)

I'm regularly doing 300km one way on German Autobahn's. I did it with peak 130km/h in the past but now do peak 190km/h. It doubles the fuel consumption but feels to save me the trip down from 3:30 hours to 2:30. That's quite a lot.

130km/h peak is way too slow if you ask me and 190km/h is way too fast for regular daytime traffic. In my time in Germany 140km/h was the 'comfort cruising speed' meaning even if I didn't look at the speedometer for a long time, I'd probably find myself driving about that.

The problematic part is that even though there's no speed limit (unless posted), a lot of speed limits _are_ posted in Germany (depends on where you live but generally the more populated areas have speed limits of 130, 120, 100 or 80, even on the Autobahn). Also, during the day in most areas you will have enough traffic that going 190km/h is not really safe. It only needs one 140km/h driver (like me :)) that switches from the middle lane to left lane, because they want to pass some dumb 100km/h guy for you to have to hit the break real hard.

For context for people that don't know, Germany does not allow passing on the right and generally on weekdays the right lane is basically solidly taken over by trucks anyway (they aren't allowed to drive on weekends, except for some exceptional cases). So you have all the "middle lane drivers" you know from NA driving in the middle lane and passing on the left lane. Trucks are also limited to 80km/h even if no speed limit is posted. But it's not a technical limit, they just aren't allowed to drive faster, which in practice means most go at 90km/h. If one actually goes at 80km/h you will have all the other trucks trying to pass that guy and some trucks with extra heavy loads just can't really go faster or are even slower. So you basically, during weekdays, have both the right and middle lane taken over by trucks, which take a looooong time/stretch of road to pass each other. It's called an "elephant race".

Guess what that does to all the 100km/h slow drivers? Right, they drive on the left lane too! Also, the German Autobahn is specifically _not_ made straight, like NA highways usually are. They actually specifically designed it to have a bend after a certain stretch of Autobahn to keep you on your toes and not bore you to sleep (and eventually death).

Now you come along with 190km/h from the back. Around a bend. With two trucks on the right and middle lane and a 100km/h grandma on the left. Good luck!

(that said, going 200km/h is awesome, I've done it. But please do it when there's "no" traffic and no trucks)

It really matters on time and location. I've been going on two way lanes in the night where the average speed on the left lane was 180km/h and on the right lane probably 120km/h. This is probably the most secure and comfortable situation for speeding.

One thing which bothers me when people talk about going fast with their cars is that it really depends on your car. I've seen high-end cars with 6 gears where the engine is absolutely relaxed when going 150km/h, especially with a Diesel. One popular example are Mercedes Sprinter, who really need very few fuel even for large speeds. Other cars (not neccessarily smaller, but for instance with petrol engine and also 6 instead of 5 gears) are already quite expensive in fuel need at this speed.

You already cover the differences in fuel consumption. But this reminds me of another difference.

In my Skoda Fabia (petrol - 5 gears) at the time, doing 200km/h wouldn't have been much fun and would probably have felt insecure too. Lots of rattling probably etc. The VW Passat Diesel (6 gears), it basically felt like a comfortable cruising speed.

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