Michigan Lefts outside Michigan

[tradephoric]

Sometimes a picture can be worth a thousand words (all these examples can be found along Big Beaver Road in Troy, Michigan).   

Michigan Left intersection:


Superstreet intersection with direct left turns from the major road:


Superstreet intersection with no direct left turns.

[Kacie Jane]

So US 65 is an example of a superstreet and not Michigan lefts, precisely because there's no median crossing?

[NE2]

If you were to draw the red and green arrows from the US 31 diagram on to the map of US 65, you'd see that the left turns do in fact work exactly the same.  The only movement that's not identical to a Michigan left is the straight across on the crossroad.

Exactly. But it's illogical to use the same term for two configurations, one of which is extremely common and the other of which is relatively rare, especially outside Michigan.
Post Merge: August 26, 2012, 12:21:26 AM

So US 65 is an example of a superstreet and not Michigan lefts, precisely because there's no median crossing?

Yes, though there's probably an anal distinction between superstreets and older similar configurations, like with roundabouts vs. circles.

[Scott5114]

So US 65 is an example of a superstreet and not Michigan lefts, precisely because there's no median crossing?

Yes, though there's probably an anal distinction between superstreets and older similar configurations, like with roundabouts vs. circles.

For one thing US 65 isn't a street. Remember when we discussed this, at length, for several months?

[kphoger]

So US 65 is an example of a superstreet and not Michigan lefts, precisely because there's no median crossing?

Yes, though there's probably an anal distinction between superstreets and older similar configurations, like with roundabouts vs. circles.

For one thing US 65 isn't a street. Remember when we discussed this, at length, for several months?

Perhaps it's not a street (debatable), but that doesn't change the type of intersection.  After all, Missouri isn't in Michigan; by the same reasoning, it shouldn't be called a Michigan left either.

[tradephoric]

Here are a couple of videos down Big Beaver Road that demonstrate how a combination of Michigan lefts and superstreets can provide good two-way progression.

Offpeak Drive (runnin a low cycle length)

Rush Hour Drive (running a high cycle length)

Michigan left intersections are represented by red dots in the aerial and are spaced 1-mile apart.  The green dots represent superstreet intersections.  Although there are many randomly spaced superstreet intersections they can easily be coordinated to the main-intersections since superstreets only stop one direction of travel.  It is crucial to have equal distances between major intersections (the red dots) when trying to achieve 2-way progression.  Cities like Atlanta or Boston which have a rats nest of arterials would be very difficult to achieve good 2-way progression (major intersections are randomly spaced).  On the other hand, cities like Phoenix and Toronto with their very defined grid networks have the potential to achieve good 2-way progression.

Now time for some simple math.  At 45 mph (the speed limit on Big Beaver) it takes 80 seconds to travel 1-mile.  To achieve good 2-way progression a cycle length of 1x or 2x the travel time between the major signals being coordinated should be selected.  In this example, a cycle length that achieves good 2-way progression would be either 80 seconds (1X travel time between signals spaced 1-mile apart) or 160 seconds (2X travel time between signals spaced 1-mile apart).   Now cut the distance in half and signals spaced only 0.5 miles apart have a desired cycle length of 40 seconds or 80 seconds. Unfortunately, even for a simple 2-phased signal an 80 second cycle isn't an efficient cycle length to run during rush hour (lost time due to yellow and all red safety minimums for each phase and time for drivers to start rolling at the start of green leads to too much waisted time).  Unfortunately, there are a lot of high speed arterials in America that have irregularly spaced traffic signals stopping both directions of travel (often spaced ½ mile apart)...a worst case scenario for achieving good 2-way progression.

Here's what a time-distance diagram of Big Beaver Road would look like when running an 80 second dial:

[tradephoric]

Michigan Left near downtown Denver (traveling SB Speer Blvd to EB Auraria Pkwy):

https://www.google.com/maps/@39.7480317,-105.003232,152m/data=!3m1!1e3

[vtk]

Michigan Left near downtown Denver (traveling SB Speer Blvd to EB Auraria Pkwy):

https://www.google.com/maps/@39.7480317,-105.003232,152m/data=!3m1!1e3

Looks like a candidate for Redesign This

[jakeroot]

Michigan Left near downtown Denver (traveling SB Speer Blvd to EB Auraria Pkwy):
https://www.google.com/maps/@39.7480317,-105.003232,152m/data=!3m1!1e3

Looks like a candidate for Redesign This

This is the best I could come up with. I really like Denver's arrow so I sort of kept that:

[tradephoric]

Draper, Utah has a Michigan Left with some unique signage:

https://www.google.com/maps/@40.5266827,-111.8885979,150m/data=!3m1!1e3

[tradephoric]

Here is a combination of a continuous t-intersection and a median-u-turn with a bulb out.  Never seen anything like this before in Michigan.

Draper, Utah crossover:

https://www.google.com/maps/@40.5250312,-111.8888693,97m/data=!3m1!1e3

[tradephoric]

There is a Michigan Left in Fishers, Indiana.  It sounds like it has been well received.


http://fox59.com/2013/11/08/fishers-drivers-like-michigan-left-turn/

[jp the roadgeek]

Just experienced my first Michigan left ever...in Metairie, Louisiana.  Funny thing is I commented to the guy next to me on the bus that what we were doing was called a "Michigan left", and guess where the gentleman was from.  Yup..Michigan.

[tradephoric]

Signage for a superstreet intersection in Mexico:

https://www.google.com/maps/@32.2739137,-115.322533,431m/data=!3m1!1e3

[tradephoric]

The Michigan Left can be found in Tuscon at the intersection of Ina & Oracle (direct lefts are still permitted for NB & SB Oracle Road).   Intersection was converted in 2013.

https://www.google.com/maps/@32.3370917,-110.9767011,215m/data=!3m1!1e3

[jakeroot]

Here is a combination of a continuous t-intersection and a median-u-turn with a bulb out.  Never seen anything like this before in Michigan.

Draper, Utah crossover:

https://www.google.com/maps/@40.5250312,-111.8888693,97m/data=!3m1!1e3

Reminds me of a roundabout with cut-throughs.

[billtm]

There is a Michigan Left in Fishers, Indiana.  It sounds like it has been well received.


http://fox59.com/2013/11/08/fishers-drivers-like-michigan-left-turn/

I'm pretty sure its the first one in Indiana.

[cpzilliacus]

Md. 3 (Crain Highway) in Gambrills, Anne Arundel County, has Michigan lefts at the intersection with Waugh Chapel Road (west side) and Riedel Road (east side).

GSV here (note that Google has missed the U turn ramp on the south side of the intersection, but I can assure you it has been there for several years now).

[tradephoric]

Median U-Turn Intersection: (AKA MICHIGAN LEFT)
http://www.fhwa.dot.gov/publications/research/safety/09057/

Restricted Crossing U-Turn Intersection: (AKA SUPERSTREET)
http://www.fhwa.dot.gov/publications/research/safety/09059/

The MD. 3 example is a Superstreet since through traffic is restricted/rerouted.  A "Michigan left" is used to describe the intersection operation as a whole and not just how the left turn movements are made.  The big thing to remember is a Michigan Left (intersection) allows through traffic to travel straight through the intersection unimpeded. 

[cpzilliacus]

Median U-Turn Intersection: (AKA MICHIGAN LEFT)
http://www.fhwa.dot.gov/publications/research/safety/09057/

Restricted Crossing U-Turn Intersection: (AKA SUPERSTREET)
http://www.fhwa.dot.gov/publications/research/safety/09059/

The MD. 3 example is a Superstreet since through traffic is restricted/rerouted.  A "Michigan left" is used to describe the intersection operation as a whole and not just how the left turn movements are made.  The big thing to remember is a Michigan Left (intersection) allows through traffic to travel straight through the intersection unimpeded. 

Was not aware of the difference. 

But given the above, I think U.S. 29 (Colesville Road) at Md. 193 (University Boulevard) in Four Corners, Silver Spring, Montgomery County qualifies.

[tradephoric]

^I'm really intrigued by this design.   Colesville Road functions as a Michigan Left and University Blvd functions as a Town Center Intersection (TCI).  If this were a typical 4-phase intersection, the splits might look something like this when running a 120 second cycle:

A phase — 50 seconds
B phase — 20 seconds
C phase — 30 seconds
D phase — 20 seconds
(where A=Colesville Thru, B=Colesville LT, C=University Thru, D=University LT).

With the current design, the splits might look something like this:

A phase — 90 seconds
B phase — 30 seconds
(Where A =Colesville Thru, B= University Thru)

Sure, people on Colesville Road are going to complain that they can't make a direct left turn.  However, instead of only getting 41% (50/120) green time for Colesville Road and taking multiple cycles to make it through the light, they now are getting  75% (90/120) green time.  Removing the left turn phases has a huge effect on increasing input.

[cpzilliacus]

Sure, people on Colesville Road are going to complain that they can't make a direct left turn.  However, instead of only getting 41% (50/120) green time for Colesville Road and taking multiple cycles to make it through the light, they now are getting  75% (90/120) green time.  Removing the left turn phases has a huge effect on increasing input.

Agreed.  It helped traffic on U.S. 29 (Colesville Road).  A lot.

[SSOWorld]

Why not? Like roundabouts, once people get used to them, they make perfect sense.

Wisconsin, in particular, needs to adopt them. They have a ton of divided boulevards and highways with left turns made at the intersection that holds up traffic flow.

Ask and you shall receive...

Two so far: one is on WIS 29 at CTH VV near Green Bay (has all cross traffic take a right-left-right while left-turning from 29 has left-turn "ramps", the other has all turning traffic turn right then left and left turns off WIS 23 at CTH M pass the intersection and turn there as well.

[JREwing78]

Why not? Like roundabouts, once people get used to them, they make perfect sense.

Wisconsin, in particular, needs to adopt them. They have a ton of divided boulevards and highways with left turns made at the intersection that holds up traffic flow.

Ask and you shall receive...

Two so far: one is on WIS 29 at CTH VV near Green Bay (has all cross traffic take a right-left-right while left-turning from 29 has left-turn "ramps", the other has all turning traffic turn right then left and left turns off WIS 23 at CTH M pass the intersection and turn there as well.

We just toured that section of Hwy 29/32 west of Green Bay yesterday during the NE Wisconsin meeting. It is very nicely done.

I suspect the locals might have trouble getting on Hwy 29 here during Packers game days, but otherwise this setup should do nicely. 

[jakeroot]

Why not? Like roundabouts, once people get used to them, they make perfect sense.

Wisconsin, in particular, needs to adopt them. They have a ton of divided boulevards and highways with left turns made at the intersection that holds up traffic flow.

Ask and you shall receive...

Two so far: one is on WIS 29 at CTH VV near Green Bay (has all cross traffic take a right-left-right while left-turning from 29 has left-turn "ramps", the other has all turning traffic turn right then left and left turns off WIS 23 at CTH M pass the intersection and turn there as well.

It's never to late to reply, but 4 years is a long time.