Ian Bicking: the old part of his blog

Re: Transit and energy intensity comment 000

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.

Comment on Transit and energy intensity comment 000
by 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