One of the themes readers will discover in Traffic is the idea that slower can be faster. Ramp meters on highway entrances, for example, keep the mainline flow going more smoothly by temporarily holding up drivers on the ramps. The individual driver suffers a moment of time loss, but the whole system moves better.
I’m in D.C. for the day, and I’ve been interested to note that an idea that’s had success in places like England’s M25 motorway is being introduced here. It’s called “variable speed limits” (wait, aren’t they all variable, you’re asking?), and the basic idea is that when a section of highway has become congested, rather than having upstream vehicles simply drive at full speed into the gelling pack, those drivers are given instructions to drive at specific speeds, lower than the typical speed limit. Instead of driving into a stop-and-go mess (in which a lot of time and fuel is wasted stopping and restarting), following cars approach at a slower, smoother pace. When the new speeds are obeyed (in the U.K. they’ve mounted cameras to enforce this), engineers have found they can achieve greater “throughput” through bottlenecks.
It’s counterintuitive, but slower is faster. As individual drivers, we pursue our immediate interest, which is to get ahead as quickly as possible. But in traffic, this works against the system as a whole. As Phil Goodwin once described it in another context, “It is one of those cases where Adam Smith’s individuals pursuing their own best interests do not add up to Jeremy Bentham’s greatest good for the greatest number.” These sorts of initiatives, which are lumped under the heading of “ITS,” are just one of the ways we can “think,” and not build, our way out of congestion.
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