The Michigan Left

[Jamzor the Jaxxor]

I can't say I've seen more than a single roundabout in Texas. That roundabout, which I have dubbed the Great Roundabout of North Texas, is a little thing behind my old high school where traffic leaving the school parking lot was directed.

[Seperallis]

Except that in the past couple of years, MDOT has started to move towards more roundabouts. We have two in Kalamazoo, they're putting in a third, Mattawan  has two and one on M-43 between Kalamazoo and South Haven. Problem is, no one around here knows how to use them yet so they have caused more problems than they solved.

If the people know the driving manual they allegedly read when they went in to get their license, they should know how to use them. We don't blame guns for the terrible acts of ignorant gun owners, do we?

I love roundabouts. I feel they're the greatest traffic invention of all time...except for, you know, the paved road. Totally being subjective of course. They do have a wonderful way of making dangerous 4-way stops safer. I forget where, but some stop here in SC in some town somewhere was notorious for people just ignoring the stop and blowing through it; needless to say, that intersection had a lot of traffic deaths every year. They installed a roundabout some years ago, and both accidents have dropped dramatically and there hasn't been a single death...because even if there is an accident, they're having to slow down for the roundabout enough that people don't get hurt.

I mainly like them because it saves gas and commute time to not have to come to a full stop at a 4-way that has no traffic.

Poorly designed ones have problems. Another roundabout somewhere down here pissed truckers off all the time because it wasn't designed to accommodate a truck towing a 54' container trailer, so they had to take the long way around that intersection on their routes. I think they fixed it relatively recently, adding a paved section inside the driving lane for truck trailers to hop onto if needed.

[Flo]

I looooooooooooove traffic circles, but yeah, when people are ignorant and dont follow the signs you have problems.

To me, that's a user error, not a systems error. People need to learn

[Seperallis]

On the topic of traffic engineering and interchanges, I came across another one today that I'm really excited about because I'm a boring old adult: the "diverging diamond." This dude has a great video on it (and I think I might subscribe to him for other things too), but the concept is, once again, to keep traffic moving and reduce wait times. It's most common use is to alleviate problems at popular intersections between a highway/interstate and an over/under-crossing arterial street.





The biggest problems at these popular interchanges is 1) the increased danger of mishaps as you try to make turns across traffic lanes, and 2) the huge delays to traffic flow by having to accommodate turns across traffic lanes. The conventional method of designing an interchange is to have two four-way traffic lights, one on either side of the bridge that spans the larger interstate/highway; as we already know from the Michigan Left solution, reducing the number of cycles for the light reduces wait times. But what if you can not only keep highway traffic flowing without a stop, but also eliminate all but two lights and make it so two directions ever stop?



Only the people going straight through on one of the roads ever have to stop, meaning the cycle only has two lights. In the meantime, all turning traffic has unobstructed lines of sight to make their turns, and are never attempting to make a turn across oncoming lanes of traffic. I think this has a huge advantage of traffic flow over a Michigan left for many situations. Hell, depending upon your needs and traffic flows you could even implement roundabouts into the pattern and eliminate all traffic lights.

This shit's fascinating, yo. This is what gets me excited in my old age. Talk civil engineering with me:
http://imgur.com/gallery/VPHBI
http://www.youtube.com/watch?v=HD-0QnUlLOQ
http://i.imgur.com/XOWrJlf.jpg