Queuing Theory: Eliminating Left-Hand Turns And Empty Cabs

The NY Times this week has their wonderful Annual Year In Ideas in the New York Times magazine. One that caught my eye was about UPS working to eliminate left-hand turns, in order to save both time and money, and indirectly, go gentler on the environment:

[from Left-Hand-Turn Elimination - New York Times by Joel Lovell]

[...]

Last year, according to Heather Robinson, a U.P.S. spokeswoman, the software helped the company shave 28.5 million miles off its delivery routes, which has resulted in savings of roughly three million gallons of gas and has reduced CO2 emissions by 31,000 metric tons. So what can Brown do for you? We can’t speak to how good or bad they are in the parcel-delivery world, but they won’t be clogging up the left-hand lane while they do their business.

Applying queuing theory in a green way may be simply good business.

As I was heading to the Oakland airport the other day by cab, I was thinking about the ecological impacts. I usually take the BART, but I was more pressed for time than usual. I asked the cabbie how often he drove there, and he replied only once or twice a day. When I had asked an Oakland cabbie a few weeks ago, he said he drove across the bridge to San Francisco four or five times a day. And then, in both cases, back to where they started, driving empty on the return leg.

I don't know the complete numbers, but I bet there are several thousand cabs in the Bay Area that travel once a day or more to other locales -- such as airports, hotels, business meetings, sporting events -- from which they are barred from taking return fares.

The rationale is that a densely populated city like San Francisco would be crushed with cabs from San Mateo, or Marin county, since the drivers would naturally gravitate to where the people are. So the many municipalities in the Bay Area have municipal laws to block outside cabbies from picking up -- but not dropping off -- in their towns. These laws were enacted in an era when the ecology wasn't a serious concern.

Now, of course, we care very much about all that carbon we are dumping into the air.

These laws have to be rethought, using the same sorts of queuing theory that UPS applies. For example, imagine a regional system where cabbies were licensed to work anywhere in the Bay Area. All the cabs would be part of an open network in which traffic information and other helpful data -- like average wait time for cabs at the airport -- would be made available, and each cab company could also have private infromation distributed to its drivers, like pick-up orders.

They would start their shift wherever they pick up their cabs, and would be free to dopr off and pick up anywhere within the region. However, they would have to follow rules designed to minimize congestion in denser areas, to keep cabs distributed, and to minimize empty cabs on the roads, polluting and increasing traffic:

1. Once a cab drops off a fare, they have to go to one of the three closest cab stands, and park, with the engine off.
2. If they do not get a pick-up or a walk-up client within some period of time (based on location and time of day), they would be directed to cab stand in another nearby sector of the region with a greater likelihood of business. And then, the rules of step one apply, again.

But, under no circumstances would we have thousands of empty cabs going from one municipality back to another. It's bad enough to pay $100 to take a cab from San Jose Airport to San Francisco, as I did a few years ago; but it's even worse to think of the empty cab driving back an hour and twenty minutes through rush hour traffic.

This is exactly the sort of thing that Swartzenegger is good at. I hope he turns his attention on it, uses San Francisco as a model, and exhorts the world to follow. Likewise Al Gore, who is is at least an occasional San Franciscan, should pound the lectern about this a bit.

And I bet the cabbies would welcome this, because they would make more money. They pay for their gas, out of their profits. The time they spend driving back from San Francisco to Oakland is factored into the meter, sort of. But the longer you are driving without a fare the odds that you will be stuck in traffic with the meter off goes up. So they would benefit.

In principle, some of the savings could be passed along to the consumer, as well, since there would be less time when cabs are burning gas, wearing out tires, etc., with the meter off. Some of that could be returned to consumers as lower fares.

This could be a true win-win-win: better for the cabbies, better for the consumers, and better for the environment in two major ways: lessened congestion and decreased pollution.

How come I haven't heard anyone suggesting this before? Does it require a master's degree in computer science to figure this out?

Please spread the meme, which I am calling No Empty Cabs.