User:Davielde/Michigan left

(DRAFT) Michigan left

A “Michigan Left“ is a procedure involving an indirect left turn onto or from a split roadway onto another road where the direct left turn is prohibited at the intersection itself. A Michigan Left can only occur at the intersection with a cross street. Other median u-turns may be available at crossovers along a split road, however these would not be classified as Michigan Lefts since they simply facilitate going the opposite direction along the same split road. Reference figures showing both types of median u-turns together appears in the Median U-Turn Guide below.

To execute the turn, the driver proceeds through the intersection to turn left at the next median u-turn, then turns left onto the same road (in the opposite direction), and finally turns right at the main intersection. Alternatively, if the intersection involves turning onto a split cross road, the driver could also turn right onto the intersecting split road, then turn left at the median u-turn, finally turning left onto the road and proceeding through the main intersection.

This procedure has proliferated in Michigan since the late 1960's and is locally referred to as a “Michigan Left Turn (MLT)” or just "Michigan Left (ML)", even in locations other than Michigan. The Michigan Left and its variants are now used or being considered in several states and other countries.

In addition, there are a number of related procedures directed toward the same or a similar result as the Michigan Left:

• “J-turn” (link to separate J-turn page)
• “Jughandle” (link to AGC and/or create separate page?)

In order to be considered a Michigan Left (or variant), proper signage should be in place prior to or at the median crossover. Depending on what entity maintains the road, however, the quality of signage will vary.

A Michigan Left in Waze typically only requires editing the median u-turn segment according to the follow guidelines:

• Naming Convention: to [street name] [opposing direction] / to [cross street name] [direction]
  • This may vary by locale, but standards should be consistent within a state or at least within a metropolitan area. Depending on whether the median u-turn is signed or locally called something else (i.e. explicitly signed "U-Turn"), the naming convention from Michigan may or may not be appropriate
  • Similar to highway way-finder segments, the “street name” is instructional rather than official
  • Example intersection of Mound Rd and Metro Parkway
    • Driving north on Mound Rd: "to Mound Rd S / to Metro Pkwy W"
    • Driving south on Mound Rd: "to Mound Rd N / to Metro Pkwy E"
    • Driving west on Metro Pkwy: "to Metro Pkwy E / to Mound Rd S"
    • Driving east on Metro Pkwy: "to Metro Pkwy W / to Mound Rd N"

• Road Type:  Ramp 
  • Although this departs from traditional rules for at-grade connectors and for use of the ramp road type, it hides the instructional street name in the client. It is close to the exception stated on the at-grade connector page, however, in that a Michigan Left is a signed--though unnumbered--exit from the current direction of travel on a roadway.

• Junction Angles: Between 45 and 90 degrees for the first turn instruction, while the second instruction may vary based on local usage
  • In Michigan, the angles for the median u-turn should generate two "turn left" instructions (both angles between 45 and 90 degrees). The first “turn left” should occur prior to entering and the second should occur while exiting the median crossover. While the first angle should always generate a "turn left", geometry standards for the exit node should be set according to the geometry of the U-turn segment itself. Typically, a particular locality will have its own standards for construction.

• Junction Position:
  • The initial junction ideally should be as close to the start of the solid white line as possible (if present). This prevents a turn instruction from occurring too early or too late. In many cases, this will require adding a geometry node at the start of the segment at the most detailed zoom level to generate the correct turn angle.

Sample Michigan Left median u-turn as it appears in Waze Map Editor:

Michigan Left Median U-Turn Guide

Description	Image
Dedicated median u-turn for the Michigan Left.
In addition to turning left onto the main road, the median u-turn also allows an option to continue straight onto a street or parking lot road. Dual segments with single endpoint at the origin. The street segment should have a turn restriction (red arrow) for the left turn since this turn is served by the other segment. Verify that the segment between destination endpoints meets or exceeds the recommended minimum length of 5m.
In addition to turning left onto the main road, the median u-turn also allows two-way traffic entering or exiting a street or parking lot road. Dual segments with no shared endpoints. This should always involve a traffic control device. Verify that the segments between endpoints meets or exceeds the recommended minimum length of 5m.

Remove this section when appropriate Working list of redirects for Michigan Left

• Arizona parkway
• Boulevard turnaround
• Median u-turn crossover
• Median u-turn intersection
• Median u-turn intersection treatment
• ThrU-Turn intersection
• MUTI
• ThrU-Turn

Separate page for J-turn

Working list of redirects for J-turn

• Continuous flow intersection
• Reduced conflict intersection
• Reduced crossing u-turn intersection
• Super-street median crossover
• Superstreet
• RCI
• RCUT