The case for almost never turning left while driving

[cpzilliacus]

Washington Post: The case for almost never turning left while driving

Left turns are unsafe for everyone.

Federal data have shown that 53.1 percent of crossing-path crashes involve left turns, but only 5.7 percent involve right turns. That's almost 10 times as many crashes involving left turns as right. A study by New York City's transportation planners concluded that left-hand turns were three times as likely to cause a deadly crash involving a pedestrian as right-hand turns. And 36 percent of fatal accidents involving a motorcycle involve a left-hand turn in front of a motorcycle, according to the National Highway Traffic Safety Association.

Engineers don't like left-hand turns.

Tom Vanderbilt, author of the popular book Traffic, has called left turns "the bane of traffic engineers."  Solutions such as diverging diamond interchanges have been proposed.

UPS: A case study in why left turns are rarely needed.

Ask any driver if they think they'd get to their destination faster and burn less gas if making almost no left-hand turns. Their answer will almost certainly be no.

Then consider the opinion of one of largest shipping and logistics companies in the world, which stakes millions on efficiency. UPS has chosen to minimize and sometimes eliminate left-hand turns to be more efficient. The company says the changes have helped it save millions of gallons of fuel. Whose opinion should we trust?

[agentsteel53]

Ask any driver if they think they'd get to their destination faster and burn less gas if making almost no left-hand turns. Their answer will almost certainly be no.

Then consider the opinion of one of largest shipping and logistics companies in the world, which stakes millions on efficiency. UPS has chosen to minimize and sometimes eliminate left-hand turns to be more efficient. The company says the changes have helped it save millions of gallons of fuel. Whose opinion should we trust?

both statements may very well be true.  UPS minimizes left turns because they have, for a given network, dozens of trucks delivering thousands of packages every day. 

the probability that UPS can eliminate a left turn by rearranging the schedule and order of visits of a given truck increases as the number of necessary destinations increases.

I have one car and probably no more than 6-10 destinations at the absolute most.  I can probably finagle them around a bit... but what if on a given day, I have the minimal case of only one destination?  I'm not gonna be able to avoid every left turn.

(that said, there's a reason why I have learned to run my lunchtime errands on a particular schedule as to minimize stops at traffic lights, left turns, etc - and part of that schedule is to not run errands nearly every day: usually I wait 'til I have three or four destinations.)

another point to note: non-protected permissive left turns are exceedingly rare in California.  if I were in a state where left turns did not default to forbidden whenever they were not permitted, then I probably would shave many minutes off my tasks every day.  but hey, I'll happily think of all the children, each individually and by name as I'm sitting there waiting for some 8-phase monstrosity to cycle through to me.

[PHLBOS]

But yet... many full-cloverleaf interchanges are now being redesigned/configured to have left-turn freeway entrance ramps.  Go figure.

[roadfro]

But yet... many full-cloverleaf interchanges are now being redesigned/configured to have left-turn freeway entrance ramps.  Go figure.

Lesser of two evils: Left turns on side street -or- weaving patterns on freeway and side street.

[Brandon]

That's why MDOT invented and implemented the Michigan Left.  The goal was to minimize left turn accidents and improve traffic flow.  It's tragic and bizarre, IMHO, how other DOTs have not picked this up and implemented it to the same extent as MDOT.

[DaBigE]

Wisconsin is beginning to go on a Michigan Left (or as WisDOT is going with "J-Turn") binge...though, not as much of a binge as roundabouts. To-date, I believe there are about a half-dozen of them on the WisDOT system with several more in planning stages.

[vdeane]

The UPS system only works because a driver would have hundreds of stops each day and each area has several trucks.  I looked at a few of my errands and concluded that I could eliminate left turns for none of them without increasing the trip time significantly.

[jeffandnicole]

That's why MDOT invented and implemented the Michigan Left.  The goal was to minimize left turn accidents and improve traffic flow.  It's tragic and bizarre, IMHO, how other DOTs have not picked this up and implemented it to the same extent as MDOT.

The Jersey Jughandle is even better: for a left turn and when placed after a traffic light, motorists only make a single right turn, and merges in to traffic to continue straight thru the light. Added bonus: keeps the left lane clear of people slowing down.

[vdeane]

That's why MDOT invented and implemented the Michigan Left.  The goal was to minimize left turn accidents and improve traffic flow.  It's tragic and bizarre, IMHO, how other DOTs have not picked this up and implemented it to the same extent as MDOT.

The Jersey Jughandle is even better: for a left turn and when placed after a traffic light, motorists only make a single right turn, and merges in to traffic to continue straight thru the light. Added bonus: keeps the left lane clear of people slowing down.

Except then people turning left have to go through two light cycles instead of just one.

[tradephoric]

Wisconsin is beginning to go on a Michigan Left (or as WisDOT is going with "J-Turn") binge...though, not as much of a binge as roundabouts. To-date, I believe there are about a half-dozen of them on the WisDOT system with several more in planning stages.

Median U-turn intersection (a.k.a. Michigan left):


Restricted crossing U-turn intersection (a.k.a. J-turn or superstreet):


Wisconsin is starting to push for Restricted crossing U-turn intersections.

[Duke87]

In an urban grid it is usually plenty possible to avoid making a left by making three rights. But there is usually not any particular impetus to do so except in cases where left turns are banned.

Although when you introduce one way streets, things get interesting. I live on a one way street. To get to the block in front of my apartment from the highway, I can either make a right and two lefts, or I can make three rights. I did the former after I first moved here since it's slightly shorter and thus more intuitive, but I've since learned to do the latter because it's actually faster - there is less of a time penalty to the right turns since I don't have to wait for oncoming traffic to clear before making them, and the extra distance is minimal.

[getemngo]

Median U-turn intersection (a.k.a. Michigan left):

...

Restricted crossing U-turn intersection (a.k.a. J-turn or superstreet):

...

Wisconsin is starting to push for Restricted crossing U-turn intersections.

Hmm... how would you classify the strictest version of all, where all traffic making any movement across the median must use crossovers? (Michigan example)

The Jersey Jughandle is even better: for a left turn and when placed after a traffic light, motorists only make a single right turn, and merges in to traffic to continue straight thru the light. Added bonus: keeps the left lane clear of people slowing down.

Except then people turning left have to go through two light cycles instead of just one.

It's possible to get stuck at 3 red lights when making a Michigan Left (once at the main intersection, once at the crossover, then again at the main intersection). The Michigan Left's biggest advantage over a jughandle is that it takes up less real estate.

[tradephoric]

Hmm... how would you classify the strictest version of all, where all traffic making any movement across the median must use crossovers? (Michigan example)

A Restricted crossing U-turn intersection with no direct left turns.


Combining Michigan lefts at major intersections and J-turns at mid-block intersections can really provide good progression along a corridor.  There are many corridors in metro Detroit where you can travel several miles (in either direction) without getting stopped at a red light (Telegraph, Woodward, Big Beaver, Northwestern, Mound Road, 8 Mile Road to name a few). 

[english si]

It only really works in grids.

If I did three lefts out of my road its a 4.3 mile loop and I end up in the same place, facing the same way as one left!

I believe it would take me 49 miles and 73 minutes of no-right-turns to simulate a right turn out of my house!

[Brandon]

It only really works in grids.

If I did three lefts out of my road its a 4.3 mile loop and I end up in the same place, facing the same way as one left!

I believe it would take me 49 miles and 73 minutes of no-right-turns to simulate a right turn out of my house!

The Public Land Survey System (PLSS) does have its advantages. 

[jeffandnicole]

That's why MDOT invented and implemented the Michigan Left.  The goal was to minimize left turn accidents and improve traffic flow.  It's tragic and bizarre, IMHO, how other DOTs have not picked this up and implemented it to the same extent as MDOT.

The Jersey Jughandle is even better: for a left turn and when placed after a traffic light, motorists only make a single right turn, and merges in to traffic to continue straight thru the light. Added bonus: keeps the left lane clear of people slowing down.

Except then people turning left have to go through two light cycles instead of just one.

Technically, they go thru the same traffic light twice, not two light cycles, and may never have to stop.  It's entirely possible to go thru a green light, then while within the jughandle the light changes, and as you approach the intersection the light is now green on the side road as well.  This is all accomplished in the same light cycle.

Even if you make it thru the green light the first time and hit the red after the jughandle, it's still the same light cycle.

The only time it would be two light cycles is when you get stopped at the red before the jughandle, and then get a red light after the jughandle as well.  Jughandles prior to the traffic light don't have this issue...but then again that would generally involve a left turn coming out of the jughandle.

[PHLBOS]

But yet... many full-cloverleaf interchanges are now being redesigned/configured to have left-turn freeway entrance ramps.  Go figure.

Lesser of two evils: Left turns on side street -or- weaving patterns on freeway and side street.

I wasn't referring to side streets per say but rather arterial highways (example: MA 9 in the Newton/Wellesley/Natick/Framingham area) that carry sizable traffic.  There are presently plans underway to convert the full cloverleaf interchange w/I-95 (MA 128) in Newton to a partial one w/signalized left-turn on-ramps to I-95.

Anyone who's traveled that stretch of MA 9 knows darn well that additional traffic signals are the last things that road needs.

[tradephoric]

Anyone who's traveled that stretch of MA 9 knows darn well that additional traffic signals are the last things that road needs.

There are 30 traffic signals along a 5 mile stretch of Big Beaver Road in Troy, Michigan.  You would think that would create horrid signal progression for drivers, but it doesn't.  Drivers get a wave of green lights in both directions of travel due to the use of Michigan lefts & Restricted crossing U-turn intersections.  I'm sure MA9 is a different animal than Big Beaver Road, but the general idea that more traffic signals leads to more stops for drivers isn't always the case.

There are presently plans underway to convert the full cloverleaf interchange w/I-95 (MA 128) in Newton to a partial one w/signalized left-turn on-ramps to I-95.

By your description, it sounds like they are going to convert the full cloverleaf interchange into a Parclo B4 interchange.  The Parclo B4 interchange functions quite similar to a Restricted crossing U-turn intersection.  The heavy use of Restricted crossing U-turn intersections along Big Beaver is a major reason why the corridor has such good signal progression to begin with (Parclo B4 is a better option with regards to maintaining good progression along MA 9 than a Parclo A4 would be).

Parclo B4 interchange in Dallas:

[cpzilliacus]

Restricted crossing U-turn intersection (a.k.a. J-turn or superstreet):


Wisconsin is starting to push for Restricted crossing U-turn intersections.

This is what Maryland DOT/SHA built to replace a conventional crash-prone intersection on Md. 3 in Gambrills, Anne Arundel County (Mapquest here).

[PHLBOS]

Some more details & info regarding the proposed changes to the upcoming I-95 (MA 128)/MA 9 interchange project; based on the write-up, I'm not the only one concerned that replacing the 2 cloverleaf on-ramps to I-95 w/signalized left turns would create a worse traffic situation than what's presently there.  There's even a petition to the Governor (Patrick) included.

[tradephoric]

Some more details & info regarding the proposed changes to the upcoming I-95 (MA 128)/MA 9 interchange project; based on the write-up, I'm not the only one concerned that replacing the 2 cloverleaf on-ramps to I-95 w/signalized left turns would create a worse traffic situation than what's presently there.  There's even a petition to the Governor (Patrick) included.

What's the alternative?  Regardless if you personally agree with it, DOT's are converting full cloverleaf interchanges to reduce weaving.  What type of interchange would you rather see constructed (assuming the DOT is dead set against keeping it a full cloverleaf)?

[Alps]

My commute would be over 5 times longer if I never turned left.

[PHLBOS]

Some more details & info regarding the proposed changes to the upcoming I-95 (MA 128)/MA 9 interchange project; based on the write-up, I'm not the only one concerned that replacing the 2 cloverleaf on-ramps to I-95 w/signalized left turns would create a worse traffic situation than what's presently there.  There's even a petition to the Governor (Patrick) included.

What's the alternative?  Regardless if you personally agree with it, DOT's are converting full cloverleaf interchanges to reduce weaving.  What type of interchange would you rather see constructed (assuming the DOT is dead set against keeping it a full cloverleaf)?

For obvious reasons, directional fly-overs are out. 

At best, a suitable compromise (since MassDOT is not eliminating every full cloverleaf interchange out there, contrary to popular belief (Highland Ave./Exit 19A-B, one exit south of MA 9, is staying as a full cloverleaf when it gets revamped)) would be to widen the MA 9 overpass enough to provide a parallel collector-distributor roads for the interchange ramps.  Such will keep the through-MA 9 traffic away from the entrance/exit ramps themselves and reduce (but not eliminate) weaving.

Truth be told, much of MA 9 (which is a 4-laner) in that area needs to be widened to at least 6-lanes as far out to the Pike interchange; but I don't see that happening anytime soon and that's another story for another thread.

[texaskdog]

Two wrongs don't make a right.  But three rights make a left.

[tradephoric]

Some more details & info regarding the proposed changes to the upcoming I-95 (MA 128)/MA 9 interchange project; based on the write-up, I'm not the only one concerned that replacing the 2 cloverleaf on-ramps to I-95 w/signalized left turns would create a worse traffic situation than what's presently there.  There's even a petition to the Governor (Patrick) included.

What's the alternative?  Regardless if you personally agree with it, DOT's are converting full cloverleaf interchanges to reduce weaving.  What type of interchange would you rather see constructed (assuming the DOT is dead set against keeping it a full cloverleaf)?

For obvious reasons, directional fly-overs are out. 

At best, a suitable compromise (since MassDOT is not eliminating every full cloverleaf interchange out there, contrary to popular belief (Highland Ave./Exit 19A-B, one exit south of MA 9, is staying as a full cloverleaf when it gets revamped)) would be to widen the MA 9 overpass enough to provide a parallel collector-distributor roads for the interchange ramps.  Such will keep the through-MA 9 traffic away from the entrance/exit ramps themselves and reduce (but not eliminate) weaving.

Truth be told, much of MA 9 (which is a 4-laner) in that area needs to be widened to at least 6-lanes as far out to the Pike interchange; but I don't see that happening anytime soon and that's another story for another thread.

I took a deeper look into the signal timing plan in the link that you provided.  According to the plans, the traffic signal for the SB I-95 on-ramp is going to stop both directions on Route 9.  This isn't necessarily bad for progression assuming that both directions on Route 9 are controlled independently from each other (IE. two traffic signals servicing each direction independently).  Unfortunately, the plan calls for one traffic signal to control both directions of traffic on Route 9, which means progression will suffer.  They are picking an interchange design which is capable of providing very nice signal progression along Route 9, yet they cheap out on the signal design so that the advantages of the interchange design aren't realized.