Wednesday, July 14, 2010

Twin Cities Traffic

Trips to new, exciting, and/or unfamiliar areas such as Minnesota (yeah!) and the Minneapolis-St.Paul area* (woo!) usually unearth some kind of traffic device or road engineering marvel that I'm not that familiar with, or that I just find interesting. For example: traffic lights at the end of interstate onramps, just before the merge.

(* - Semantics question. Is the term "Minneapolis-St. Paul" similar to the term "Raleigh-Durham" in that it is not used by anyone who actually lives there? Do the locals prefer to use the term "The Twin Cities" to refer to their home metropolitan area, just like people from our area prefer the term "The Triangle"? Those dashed metropolitan area names are pretty awkward, you know.)

Many, if not all, of the onramps onto Minneapolis-area expressways have traffic lights at the end of them. Apparently, they're called ramp meters. I guess they're supposed to control the flow traffic coming onto the expressways, in order to move the backups from the expressways themselves onto the onramps? I've never seen this anywhere else, but it seems pretty smart, and apparently, they're effective. We were never in the area during rushhour (aww, shucks), so the ramp meters were on flashing yellow the whole time when we were there.

Many onramps also have separate lanes for carpools that aren't controlled by a ramp meter. Genius! That's way easier and cheaper than building a separate HOV lane on the expressways themselves.

Here's a separate topic that has more to do with Minnesota in general. Let's say you see a sign up ahead that says "LEFT LANE CLOSED, 2 MILES", and you're in the right lane. Do you get in the left lane at the first available moment, or do you wait until the last possible moment to merge?

Well, Minnesota wants you to wait until the last possible moment to merge, and they tell you this with signs that say something to the effect of "USE BOTH LANES TO MERGE POINT". I think studies have shown that when both lanes are full to the merge point and people work together and take turns merging into one lane at the merge point, traffic moves more quickly overall. (Maybe this will only work in Minnesota because of that whole "Minnesota nice" thing.) The alternative to the Mn/DOT-endorsed merging method is a free-for-all mix of people who change lanes at the first possible moment - which often creates an unnecessarily long backup well in advance of the merge point - and people who speed ahead in the now-vacated right lane and cut in front of someone at the last moment. (Tom Vanderbilt's book Traffic: Why We Drive the Way We Do> talks about this issue at length.)

The latter situation is what happened in a construction zone on I-74 in Illinois during Day 2 of our Alaska trip. Signs warned motorists of a closing right lane several miles in advance of the construction zone. So what did people do? Move over to the left lane immediately, creating a very long backup. What did I do? I got in the right lane, moved ahead two miles unimpeded (passing up to a hundred cars in the process), and then merged into the left lane just a few hundred feet before the merge point in front of a slowly-accelerating truck. (In most traffic jams, you can usually find plenty of space to move over in front of a large truck.) Yes, I am that jerk who speeds ahead in the open lane and cuts in at the last moment. But don't blame me; blame Tom Vanderbilt and his book. He told me to do it.

So, in summary: Mn/DOT gets it. (Paying attention, PennDOT?)

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