MICHIGAN LEFT

A 'Michigan left', sometimes known as a 'median U-turn'^[1] 'median U-turn crossover',Federal Highway Administration, Alternative Intersection Treatments - Median U-Turn Crossover or 'Boulevard Turnaround'^[2] is an automobile traffic maneuver in which a unidirectional U-turn and a right turn replace a prohibited left turn. The term comes from the fact that the arrangement is quite common along Michigan roads and highways, and extremely rare anywhere else in the United States.

Contents

Description

Locations

Advantages and disadvantages

Advantages

Disadvantages

Partial Michigan Left Intersections

See also

References

External links

Description

Michigan lefts occur at intersections where at least one road is a divided highway or boulevard. Left turns onto the divided highway are prohibited. Instead, drivers on roads that cross the highway are directed to turn right. Within a 1/4 mile (400 m), they queue into a designated U-turn lane in the median. When traffic clears they complete the U-turn and go back through the intersection. For additional safety purposes, the U-turn lane is designed so traffic only flows through it one-way.
Similarly, traffic on the divided highway cannot turn left at an intersection with a cross street. Instead, drivers are instructed to overshoot the intersection, go through the U-turn lane, come back to the intersection from the opposite direction and turn right.

Locations

The Michigan left was initially piloted by MDOT at the intersection of 8 Mile Road (M-102) and Livernois Avenue^(map) in Detroit in the early 1960s. The increase in traffic flow and reduction in accidents was so dramatic that over 700 similar intersections have been deployed throughout the state since then.

Advantages and disadvantages

This type of intersection configuration, as with any engineered solution to a traffic problem, carries with it certain advantages and disadvantages and has been subject to several studies.

Advantages

★ Safety — potentially provides a major reduction in left-turn collisions and a minor reduction in merging and diverging collisions, due to the shifting of left turns outside the main intersection

★ Reduced travel times — Reduces the number of different traffic light phases, increasing traffic flow. Since separate phases are no longer needed for left turns, this increases green time for through traffic. The effect on turning traffic is mixed.

★ More options for turning — At intersections where both roads have Michigan Lefts, there is more than one way to turn left. For example it is possible to either turn right at the intersecting road, and use the U-turn to go left, or go past the intersecting road, use the U-turn on the original road, and make a right on the intersecting road. This is very useful when trying to avoid traffic lights provided there isn't a "No turn on red" sign. It also allows for an alternate path in case of a traffic-blocking incident.

★ Cost — U-turn lanes are often already present on divided highways to provide for access to businesses in the opposing direction. Hence the addition of the Michigan left turnaround is essentially free.

★ Enhanced progression — The timing of traffic signals along a highway featuring Michigan lefts is made easier by the elimination of left-turn phases both on that highway and along intersecting roadways. Thus, traffic progression through the timed signals in enhanced, contributing further to the reduction of travel times and the increased capacity of those roadways.

★ Fewer threats to pedestrians — Pedestrians crossing either street at an intersection featuring Michigan lefts only encounter through traffic and vehicles making right turns. The left-turning movement, having been eliminated, removes one source of potential vehicle-pedestrian conflict. However, the major roadway typically has a wider cross section, making said crossing longer.

Disadvantages

★ Confusing — since the scheme is rare outside of Michigan, it can be confusing to visitors expecting to be able to turn left from the left lane.

★ Inconsistent — not all intersections use the system, so drivers approaching an unfamiliar intersection do not necessarily know whether to be in right or left lane, although signage is generally placed in advance of intersections requiring such a maneuver.

★ Land use — Depending on the width of the existing median, extra land may be needed for large vehicles to make the U-turn. Additionally it may be harder to access local businesses.

★ Stress — drivers may need to quickly move across several lanes of traffic when getting into or out of the U-turn, although if traffic does not permit, typically another U-turn is available within less than a mile. The need to "quickly" move across several lanes is negated, however, when making the right turn on a green light, whereby all traffic on the cross-street is stopped.

★ Delays — specifically right turns on red. Since one cannot make a left onto a road, one has to instead make a right, cut across several lanes of traffic and merge into the U-Turn lane. With roads that have a medium amount of traffic, this means that motorists trying to make right turns are often delayed by motorists trying to go left, as their desired course of action requires a larger gap in oncoming traffic to execute. Waiting through an entire red light to make a right is not uncommon.

★ Expense — On high traffic roads, Michigan lefts may require an additional pair of traffic lights at each of the turnarounds. This may be offset, however, by the simpler traffic signal configuration at the primary intersection due to the removal of the left-turn movement's respective signal phases.

★ Visibility — Drivers inching up in the right lane of a Michigan Left may block the visibility of drivers attempting to make a turn from the left lane. This can be dealt with, however, by the left lane vehicle completing the turn at the same time as the right lane vehicle.

★ Safety – Traffic merges with opposing traffic flow at the U-turn in the fast lane, unless signalization of the U-turn provides for control of the merge point.

★ Very low traffic - Motorists driving very late at night or early in the morning who would otherwise benefit from dynamic control with a regular left-hand turn configuration are instead forced to go through the Michigan left procedure.

Partial Michigan Left Intersections

Despite the fact that in recent years many lesser-used intersections (particularly) in Southeastern Michigan have been upgraded to have Michigan lefts due in part to increases to traffic flow, there are still a few intersections there that, despite having had the Michigan left requirement for years, have at least one segment that does not require the Michigan left. Among them are:

★ Fort St. and West Rd. in Trenton - Turning onto westbound West Rd. from northbound Fort St. does not require drivers to make a Michigan left, but all other turns do. The Michigan Department of Transportation (MDOT) added this requirement in the late 1990s, but opposition from local residents and officials persuaded them to drop the Michigan left requirement soon thereafter.

★ Southfield Rd. and Dix Hwy. in Lincoln Park - Turning onto southbound Dix from northbound Southfield (which is technically running east-west through this area) does not require the Michigan left, but all other turns do. MDOT officials have twice tried to close this loophole, but again, opposition from local residents and officials foiled both attempts.

★ Telegraph Rd. and Van Born Rd. on the border of Dearborn Heights and Taylor - This has been an interesting exception for years as turning south on Telegraph from westbound Van Born and west on Van Born from northbound Telegraph have required the Michigan left, yet turns onto eastbound Van Born from southbound Telegraph and from eastbound Van Born to northbound Telegraph have not. This is because just south of Van Born is Telegraph's junction with I-94, and formerly there were K-rails dividing the road there and no room for a turnaround of any kind regardless. Nowadays, the road there is undivided for the junction's new SPUI interchange. The intersection of Van Born and Telegraph has had left turn signals of various types for the non-Michigan left turns.

See also

★ Continuous flow intersection

★ Hook turn

★ Jughandle

★ Pittsburgh Left

★ Superstreet

References

1. North Carolina State University, Unconventional Left-Turn Lanes Reduce Traffic Accidents, Congestion, August 1, 1999
2. http://www.ci.farmington-hills.mi.us/egov/docs/1098972815_561889.pdf

External links

★ The Michigan Left-Hand Turn

★ Synthesis of the Median U-Turn Intersection Treatment, Safety, and Operational Benefits