Monday, January 23, 2012

Highway Congestion

The last major participant we will cover in the Meet Rideshare series is, again, a somewhat, er, ethereal participant. It is the highway system itself, which is scarcely able to breathe at rush hour times, poor fellow, because of how clogged its “arteries”(highways) are. What kind of impact will Rideshare realistically have on congestion on the highways? The answer is, potentially, massive.

Congestion, like pollution, operates on a synergistic basis. Congestion breeds more congestion. This is because congestion forces everyone to slow down. It is amazing how fast a 65 mph highway can turn into a 5 mph in the city of Los Angeles. And the really amazing thing is just how few cars it takes to make it happen.

Highways have a capacity limit, like most networks do. They are built to hold and move a certain number of vehicles, just like cable systems are built to hold a certain number of channels or cell phones are built to move a certain number of bits per second. However, congestion on the highways differs from congestion in cable or cellular systems in one important respect: excludability.

What this means is that when a cable system doesn’t have room to add another channel, it can refuse to do so. The cable operator is coordinating the system, and makes sure that the cable system isn’t asked to carry more channels than it can handle. If a cable system tries to cram five channels into four slots, the picture will become all pixelated and distorted, and customers will not have four or five channels to enjoy. They will have zero. Congestion slows down everyone in the system, not just the newcomer there’s no room for.

Cellular networks, if asked to transmit more data at one time than they have, have a different control mechanism. They simply slow everyone’s transmission speed to the level the system will bear. But even though each individual’s transmission may move somewhat more slowly, the system itself is still working at maximum capacity. A system meant to transmit 1 Mbps for 100 people may instead transmit .5 Mbps for 20 people for example. But A total of 10 Mbps is always moving through the pipes.

Highways are different. A highway which can move 10000 cars at 60 mph cannot move 12000 cars at 50 mph. This is because each additional car on the roads forces every car on the road to move more slowly. What’s more, unlike with cable or cell systems, there is no controlling authority which can stop people from entering the highway once it’s capacity limit has been reached. So as the slower highway fails to get people to their destination, and off the highway, as quickly as before, more people are continuing to pile onto the highway, creating still more congestion which clogs the roads still further, causing the speed of the highway to be reduced again, causing more congestion, and so on. A highway which has even a little congestion on it therefore, or goes even slightly over capacity, quickly enters a death spiral, a negative feedback loop which destroys the utility of the highway for everyone.

Rideshare, however, makes this synergistic snowball effect run the other direction. Taking some cars off the road reduces congestion directly, of course, but it also has additional “knock-on” effects. Fewer cars and less congestion on the highways means that the cars that remain can move at something closer to the speed limit, covering more distance in less time and thus getting them off the highway faster. Getting them off the highway faster means that the remaining cars can move still faster, and get off the highway still faster, thus allowing the remaining cars to move faster, etc.

So you see, Rideshare doesn’t need to get that many people out of their own cars and into someone else’s to achieve a drastic reduction in highway congestion. Indeed, Rideshare’s ability to create clearer and faster highways for everyone in Los Angeles, including those who never use our service, far outweighs even our other positive social benefits. We can make a significant contribution to environmental protection and a somewhat smaller one to climate change, but Rideshare may just have the ability to all but eliminate highway congestion on its own, if we can get enough people onto our service.

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