Ian Bicking: the old part of his blog

Transit and energy intensity comment 000

Thanks for looking up the city energy intensity. Of course, it also assumes that cars have the same number of average passengers -- but honestly I have no idea if it would go up or down for city driving.

I can see why the report would omit them, give it's angle.

I don't really think the report has an angle. I do think they have specific data sources, and very possibly none of them covered city driving. I imagine it's much easier to figure out how many cars drive on highways than on city roads, and the other necessary numbers that go with that.

PRT systems look good, but will take a long time to replace the significant existing rail infrastructures we already have.

Do they have lots of existing rail infrastructure in Australia? We don't have hardly any for passenger use here. We have freight rail lines, which is what Amtrak also uses outside of the East coast, and that sucks. Much of the rail we have isn't of very high quality, and so it's not particularly fast or reliable to run on.

But PRT doesn't really have to replace existing infrastructure. There's a tremendous amount of in-fill that has to happen, regardless of the system, so there's a lot of new infrastructure that has to be built. Really it's hard to compare the two systems at that point, as no one proposes train systems with coverage anything like PRT systems. Trains simply don't scale that way -- the interchanges are difficult, and changing trains is too slow to have anything like a dense grid. It doesn't work great for Buses, but at least their stations are so cheap (i.e., just a sign) that they can provide good coverage that way. Though both trains and buses have a scaling problem where the speed of the system is slowed down by the number of stops -- so the better your station/stop coverage, the worse your travel time. PRT scales in a completely different way.

Also note that PRT infrastructure is far cheaper than traditional rail because the loads are so much less. Also because there is redundancy in the system it can be deployed incrementally, and repaired or upgraded without total system shutdowns. Rail does not do so well in that case and so repairs become extremely complicated and expensive operations.

Comment on Re: Transit and energy intensity
by Ian Bicking


One thing that would affect these figures is that US rail is far more energy intensive than the rest of the world. The US idea of a commuter train is often some huge heavy thing with its own specific locomotive, compared to the "bus-on-rails" idea in Europe for example, with an underbody engine. I think the USA could use a fraction of the energy running public transit, if they wanted. Even US buses are much heavier and bigger-engine than European for example. So this would affect these figures..........

# Nick D

If anyone had these kinds of numbers for other countries, that would be awesome.

The US idea of a commuter train is often some huge heavy thing with its own specific locomotive, compared to the "bus-on-rails" idea in Europe for example, with an underbody engine.

"Transit rail" has an underbody engine, and does worse than commuter rail (though probably for other reasons). I think US transit rail uses essentially the same vehicles as in Europe, but I don't really know.

Even US buses are much heavier and bigger-engine than European for example.

For some reason we are very reluctant to run small buses. I'm not sure why; I suspect just to make the fleet more homogeneous, and because like every other kind of transit the people making these decisions don't care about the energy use. People in the US are probably also more tolerant of the size of buses on the street, so there's no pressure to reduce the amount of space they take up.

# Ian Bicking

A big reason US trains are not is efficient is because the US is nuts about safety. Thus US trains are often twice as heavy as European trains in order to make them crash worthy. There are probably many more road-level railway crossings in the US than in Europe. Still, the US is way more strict, and I don't know how effective that really is at preventing accidents. Surely it must lengthen the stopping distance, which would be safer if it could be shorter.

# James

The best way to make our existing transit system work is to increase the density. If you can average to people per car, the efficiency goes up, congestion goes down which also helps efficiency go up. I like the PRT idea but it requires a HUGE investment in infrastructure.

We have plenty of capacity it's just not utilized well. In the morning, there's a wide river of traffic going by my house. I know that many of those people are going close to the same place that I want to go. If there was just some way to link us up, we could share the ride.

I'd like to see a dynamic carpool system. Use the GPS built into the cell phones along with the wireless network to allow people to log in their morning and evening routes. Other people needing a ride would log in their request. I computer would link up riders to available drivers and send directions to the driver to pick them up. I don't carpool now because my schedule is to random. I don't know exactly when I can leave in the evening. With a dynamic carpool, I wouldn't need to. When I'm ready, I just go down to the street and request a ride then wait for the pickup.

This system works best when there's a lot of traffic. Lots of cars increase your chance of finding someone going near to your location. It scales up when you need most capacity and avoids that round trip problem that you mentioned.

For off hours, you have a couple of thousand taxi like shuttles on non-determined routes picking up and dropping off people when they request a ride.

Look at the advantages; low or no infrastructure costs, door to door service, 24 hour service cheaper than the other methods. All you need is the software to track drivers and riders over the cell network and send the instructions to link them up. Granted, that software might be difficult to write but I don't think it's impossible.G

Getting people to participate would be the hardest part. You can use the existing carpool programs to encourage ridership. If the system caught on, you could possibly live in a western city without a car.

# Joe Goldthwaite

I like the PRT idea but it requires a HUGE investment in infrastructure.

While your car pooling idea requires less (additional) infrastructure, all rail-based transit has much higher infrastructure cost than PRT, and PRT should be cheaper than highway lanes of similar capacity. Of course PRT can't replace the flexibility of roads (which carry things like moving trucks, construction equipment, bikes, ambulances, etc), so it's not really right to compare it to basic road infrastructure (which is inevitably required); but it compares quite favorably to the cost of increasing road capacities. And as an immature technology there's more avenues open to improve it.

While responsive car pooling or taxi service doesn't require new infrastructure (instead increasing the capacity of current infrastructure) the energy intensity improvements seem limited. It would feature smaller vehicles, and by being more responsive and adaptive it could carry a higher number of average passengers. But it still requires vehicles larger than a typical car, and I imagine cars would frequently be running at less than full capacity. I wonder what the energy intensity of a normal taxi is? Probably atrocious -- they frequently drive around with no passengers at all, and tend to use fuel-inefficient vehicles. Ride share systems would certainly be a big improvement over that, and probably buses, but not a huge win. Though by using less vehicles more intensely you can afford to invest more heavily in fuel-saving vehicles or in vehicle upgrades. Anyway, an interesting idea.

# Ian Bicking

I guess the idea isn't new. Here's a paper from 1968;


# Joe Goldthwaite