11.6.09

TO UNCLOG THE EXPRESSWAYS, FIX THE ARTERIALS. I've been making this point for years.
There's something called the Law of Peak Expressway Congestion that suggests road improvements divert traffic from other roads, until travel times are the same on the improved road as they are on the unimproved roads. (Indifference at the margin, anyone?) An elaboration of the law suggests that additional capacity shortens the duration of the peak subject to the same indifference condition, which makes sense as long as the total volume of trips stays the same, but a shorter crush hour serves as an inducement for more people to relocate.
In Milwaukee, Patrick McIlheran discovers the effect, in reverse.
People flock to freeways in preference to even wide surface arterials because on most, you have to stop at least every half-mile. More than a couple miles of that, and you'll take your chances on expressway roulette.
His column focuses on spending some money (the porkulus?) to widen the arterial streets, and grade-separate some of the busier crossings (which might be more effective than dedicated left-turn lanes with arrows, an approach that makes synchronizing the green lights harder, but probably less effective than rotaries, which obviate traffic lights).

He's also got some advice for transit's advocates.
The farther you can commute in a tolerable time, the more job options you have. Economists find that faster commutes equate to considerable increases in productivity. So when planners accept rising congestion - even welcoming it as a way to drum up business for transit - they're cutting into a city's wealth.
That's worth considering. Faster transit can also produce productivity gains, although its advantage is on limited-stop service where higher speeds are possible. It's higher gasoline prices and higher parking charges that will induce more transit ridership.

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