Even with single people in cars you can move wayyyy more than 100 people per hour in the top left.
Assume 25 mph speed and 30 feet between cars, each car crosses 30 feet in about a second. 3600 seconds in an hour, times 2 for both directions and you have 7200 people that can move on that little road.
Now add additional passengers…buses…it can move a decent amount more. There’s lots of reasons cars suck but let’s not make up math to prove the point.
It’s not saying that the top row can support at most 100 people.
Just that if you have 100 people per hour, you need something like what’s in the picture. The train tracks aren’t being fully utilized in the top pic, either.
As an aside, you’re forgetting that cars are ~15 feet long on average. So you’ve got an hour of traffic with consistently 1 car following distance, which is fairly unrealistic. Real world capacy of a lane is closer to 2k people per hour, or 4k both directions.
Yeah and the big road below can hold WAY more than 10,000 too. The numbers here are all made up and it doesn’t really do a good job of making the point the creator wants to make.
Ignoring the effect of heavy vehicles and assuming a free flow speed of 70, the federal highway authority’s numbers would be 2400 vehicles per lane or 55k vehicles per hour. Assuming an average occupancy of 1.5 people per vehicle, that’s nearly 83k.
Although 83k people per hour is 41.5k people per rail track. Assuming a 360 person train like the Bombardier BiLevel Coach, that’s only 115 train cars per hour per track. If each train has 11 cars, that’s 10 trains per hour or a train every 6 min. Not really that unreasonable, and the tracks will look mostly empty unlike that monstrosity of a road.
At 25mph, the safe distance between cars is closer to 60-70 feet. Add the length of the cars for another 15-20 feet and your throughput calculations drop by a factor of 2.5-3 already.
It gets worse once you start considering comparable velocities. Trains go way over 25mph.
Also assume that no one is turning onto or off of the road?
Theoretically the highway I can see outside my window could handle tens of thousands of passengers per hour moving at over 60mph. But for some odd reason when I look out my window on workday it’s moving significantly less than 25 mph. Some days is not even moving at all.
Yeah but for long term growth is not ideal, the tracks will do a better job in long run.
No matter the math, trains move more people, faster and safely.
What you should use for your argument is that it’s easier and better to low capacity roads in rural areas (low population) than building trains to replace the car everywhere. Either way there is no argument against trains from city to city or a metro. Cars get out competed there.
Theoretical maximum saturation flow rate per lane (this will allow you to do quick calculations in your head to check reasonableness at big events): 1,900 vehicles per hour per lane
So the bottom would probably be more like 25K each way. Lightrail is only about 4-8k? Meanwhile a single subway lane each way could do more than that thing on the bottom left.
What does “should” mean in this context? Wouldn’t it depend on if you are trying to compare peak capacities or daily usages? I’d assume which one matters more would vary based on why you are comparing them in the first place?
Even with single people in cars you can move wayyyy more than 100 people per hour in the top left.
Assume 25 mph speed and 30 feet between cars, each car crosses 30 feet in about a second. 3600 seconds in an hour, times 2 for both directions and you have 7200 people that can move on that little road.
Now add additional passengers…buses…it can move a decent amount more. There’s lots of reasons cars suck but let’s not make up math to prove the point.
It’s not saying that the top row can support at most 100 people.
Just that if you have 100 people per hour, you need something like what’s in the picture. The train tracks aren’t being fully utilized in the top pic, either.
As an aside, you’re forgetting that cars are ~15 feet long on average. So you’ve got an hour of traffic with consistently 1 car following distance, which is fairly unrealistic. Real world capacy of a lane is closer to 2k people per hour, or 4k both directions.
Yeah and the big road below can hold WAY more than 10,000 too. The numbers here are all made up and it doesn’t really do a good job of making the point the creator wants to make.
Yeah.
I think I count 23 lanes in the bottom pic.
Ignoring the effect of heavy vehicles and assuming a free flow speed of 70, the federal highway authority’s numbers would be 2400 vehicles per lane or 55k vehicles per hour. Assuming an average occupancy of 1.5 people per vehicle, that’s nearly 83k.
I’m having trouble finding actual sources right now for max rail capacity, but https://en.m.wikipedia.org/wiki/Passengers_per_hour_per_direction claims 60-90k passengers per direction on 3.5 meter lanes for “suburban rail”.
Although 83k people per hour is 41.5k people per rail track. Assuming a 360 person train like the Bombardier BiLevel Coach, that’s only 115 train cars per hour per track. If each train has 11 cars, that’s 10 trains per hour or a train every 6 min. Not really that unreasonable, and the tracks will look mostly empty unlike that monstrosity of a road.
The road in the bottom picture seems to be jammed. 23 lanes are no use if there’s a bottleneck at the end.
That’s by design, and helps make the case for MOAR FREEWAY$$!
https://en.wikipedia.org/wiki/Induced_demand
when r u gonna build a traintrack outside my house plz and thank u
if u dont build a traintrack to every single house itd be a waste of time due to current scales of infrastructure.
At 25mph, the safe distance between cars is closer to 60-70 feet. Add the length of the cars for another 15-20 feet and your throughput calculations drop by a factor of 2.5-3 already.
It gets worse once you start considering comparable velocities. Trains go way over 25mph.
Also assume that no one is turning onto or off of the road?
Theoretically the highway I can see outside my window could handle tens of thousands of passengers per hour moving at over 60mph. But for some odd reason when I look out my window on workday it’s moving significantly less than 25 mph. Some days is not even moving at all.
Yeah but for long term growth is not ideal, the tracks will do a better job in long run.
No matter the math, trains move more people, faster and safely. What you should use for your argument is that it’s easier and better to low capacity roads in rural areas (low population) than building trains to replace the car everywhere. Either way there is no argument against trains from city to city or a metro. Cars get out competed there.
I don’t disagree, but we shouldn’t be pulling numbers out of our asses that are orders of magnitude different from the real figures.
Quick search gave this number:
So the bottom would probably be more like 25K each way. Lightrail is only about 4-8k? Meanwhile a single subway lane each way could do more than that thing on the bottom left.
I’m guessing you found this source: https://www.mikeontraffic.com/numbers-every-traffic-engineer-should-know/
The number from that page he should actually be using is more like this one:
(Source: I’m a former traffic engineer.)
Yup.
What does “should” mean in this context? Wouldn’t it depend on if you are trying to compare peak capacities or daily usages? I’d assume which one matters more would vary based on why you are comparing them in the first place?