Ken ~

 

I usually keep quiet, but this topic needs another 2 cents of input.  The

issue you describe below is mostly due to a circular Central Island / CID

(not striping or signing).  Striping and signing is important, but not the

problem.  Even with a "perfect" design, the 2/2/2 lane configuration (2 lane

entry, 2 lane circulating, 2 lane exit on all four legs) with a CIRCULAR CID

is the real problem because it confuses the drivers.  Avoiding a 2/2/2

roundabout with a circular CID is critical.  A non-circular CID promotes

much better roundabout operations and avoids the "Achilles' heel" you speak

about.  If drivers clearly know where the other is going by proper geometry,

those type of fender benders simply do not happen.  The attached image shows

consecutive dual lefts (SB and WB).  Despite some construction issues with

the final asphalt overlay disturbing the striping, the geometry is sound.

The original design also showed an island in the NB approach between

approach lanes (not installed).

 

Scott

 

 

Scott Ritchie, p.e.

President, Roundabout Specialist

Roundabouts & Traffic Engineering

Direct: (928) 284-0295

Main: (928) 284-0366

scott@roundabouts.us

www.roundabouts.us <http://www.roundabouts.us/>

 

 

  _____ 

 

From: Roundabout Research [mailto:ROUNDABOUTS@LISTSERV.KSU.EDU] On Behalf Of

Ken Sides

Sent: Wednesday, September 04, 2013 8:35 AM

To: ROUNDABOUTS@LISTSERV.KSU.EDU

Subject: Striping 2-lane exits from 2-lane roundabouts

 

 

 

RESEARCH TOPIC

 

 

 

Gene & Phil -

 

 

 

This seems to me like an important, timely and urgent question for research:

what's the best way to stripe and mark a 2-lane exit from a 2-lane

roundabout? 

 

 

 

1-lane roundabouts can be pretty much bulletproof.  But 2-laners have this

Achilles' heel at the exact spot in the third diagram below from the

Wisconsin DOT brochure.  You can walk out to the precise location where the

fender-benders occur over and over and place a dime on it.  And both drivers

are always completely flabbergasted by the other driver's movement.   It

would be valuable to know, once and for all, based on objective research,

including objective field studies, the best way to stripe and mark these

2-lane exits. 

 

 

 

Yes, many have conscientiously  labored hard to think it through and have

tried and/or observed various striping and marking schemes and hit on the

one each belileves is best, but what I'd like to see is overarching,

objective, credible research with field studies to settle the question for

good. 

 

 

 

-Ken

 

Ken Sides, PE

 

Ken,

 

 

 

Not everybody is doing it this way.  Attached is our detail.

 

 

 

We only break the line where cars have to cross and we move the circulatory

arrows up - hoping it will make it clearer to the car getting ready to turn

left from the right lane that they might be hit by the car going thru in the

left lane.

 

 

 

Regards,

 

 

 

Howard

 

---

 

 

-----Original Message-----

From: Roundabout Research [mailto:ROUNDABOUTS@LISTSERV.KSU.EDU] On Behalf Of

Roundabouts Roundabouts

Sent: Wednesday, December 03, 2008 3:28 PM

To: ROUNDABOUTS@LISTSERV.KSU.EDU

Subject: Yield Line

To All,

 

In NY we currently use a 1 foot wide dashed line (yield line to John Q.

Public) or circulatory roadway delineation line - engineering term....

:-(

 

We are considering going to 18" or 2' - our reasoning being that 2' is

a typical stop bar and this should have the same "value" as the stop

bar.

 

I would like to know what others are using - and why...

 

Thanks,

 

Howard

---

 

Date:    Wed, 3 Dec 2008 15:44:49 -0600

From:    Mark Johnson <mtjeng@SBCGLOBAL.NET>

Subject: Re: Yield Line

Howard,

For higher functional classification roadways,

I recommend a 18-24" wide line, with a 12" gap.

Yielding is often the most problematic operational concern.

Therefore providing emphasis for the yield point for a yield controlled

intersection seems very prudent to me.

I have anecdotal evidence from a project where one entry was having entry

circulating crashes. The yield line markings were made much wider from 12"

to 24" and a years worth of crash data show an ~80% reduction in entering

circulating crashes.

First RoundaboutFirst Roundabout

---

We use 18" preformed thermo-plastic material mainly because we use it for other things such as stop bars and crosswalks bars. 

Bill Hange

Loveland, Colorado

---

 

In Victoria, Australia, roundabout holding lines are 600mm line-600mm

space as per a normal give way (yield) line, the only difference

being the roundabout line is 400mm wide as opposed to the normal give

way being 300mm.

I can't see the reason for having 2 lines - you only have to yield

once!  Also, not good for motorcyclists when the roads are wet.

Andy

Andrew O'Brien

Principal & Managing Director

---

From:    "Kingsbury, Dwight" <Dwight.Kingsbury@DOT.STATE.FL.US>

Subject: Re: Yield Line, edge line, give way line, limit line, shark's teeth, etc.

Typical edge lines are 6" wide, but the MUTCD supports use of a wide edge line ("at least twice the width of a normal line") "for greater emphasis". What the MUTCD calls "dotted" edge lines are also used at driveways, which are also locations where entering drivers are obliged to yield. A 2' dash with a 2' gap, such as shown in the Lansing photo, is a valid "dotted" edge line extension. I certainly agree, though, that an edge line of 18" width would be unusual at driveways (a dotted edge line is supposed to be the same width as the solid edge line it extends).

Given what should be a growing familiarity with such lines, due to the spread of roundabouts, it would not be surprising if many US drivers do now associate these lines with a yielding obligation, even though such lines do not establish the obligation.

I'm not sure I've heard anyone outside the technical community refer to the dashed/dotted white lines at roundabout entrances as "yield lines". Nevertheless, it's obvious that most (US) folks on this list do think of them as yield lines, and I suspect that perception is now shared by many US drivers.

It may well be that marking of official (shark's teeth) yield lines would produce no increased rate of yielding at a roundabout's entrances, especially if the rate were already fairly high. If yielding rates have been unsatisfactory, it's also conceivable that widening the dashed lines could be as effective as adding shark's teeth, or even more so, although offhand I'm not aware of a study that has directly compared the effectiveness of the two treatments.

In any case, if wide dashed lines at roundabout entrances can adequately perform double duty, then shark's teeth would indeed be redundant in this application.

Dwight

---

From:    "Dovey, Dan" <Dan.Dovey@KINGCOUNTY.GOV>

Subject: Re: Yield Line

Howard:

We think of the yield line as a broken stop bar, so a dashed line

conveys this message best.  But our stop bars are 16" wide and when we

make our yield lines the same width they appear like boxes, as wide as

they are long.  So we use 12" wide thermoplastic and typically place a

3' dashed stripe with a 2' gap along the entry at the radius of the ICD.

We don't use shark's teeth - I'm not convinced Joe Driver has a clue

what they are anyway.

---

From:    "Dunlop, James H" <jdunlop@NCDOT.GOV>

Subject: Re: Yield Line

How is Joe Driver going to know what yield lines are if they are not used?  Isn't that the same argument that was used about roundabouts, that the public wouldn't know how to drive through them, and we'd need to install a police substation in the middle to handle all the crashes?  (That's my favorite public comment against roundabouts that I believe Gene posted a while back.)  I do agree that right now most of the public doesn't know what they are.

In North Carolina, we use the shark's tooth yield sign perpendicular to the travel lane (not curved) at the location where we would expect vehicles to stop or pause (in the process of yielding to circulating traffic) and we use a dashed curved line for the extension of the roundabout outline (completing the circle, if you would.)  This matches the 2003 MUTCD except to make the yield line straight instead of curved.

Is this doubling the markings?  Yes.  But it gets to where I think we need to be on pavement markings.

James H. Dunlop, P.E.

---

From:    "Dovey, Dan" <Dan.Dovey@KINGCOUNTY.GOV>

Subject: Re: Yield Line

James:

Our markings presume that the driver can figure out that a dashed stop

bar is, if anything, a yield line.  My impression has always been that

the shark's teeth were supplemental to the yield line, not a replacement

for it.  As for doubling the markings - I have always found that less is

more, both in the area of markings and signing.  The regulatory yield

signs are the primary device used to control the entry (with typically

two signs placed one on each side).  The striping merely indicates where

the yield needs to take place.  Do drivers need additional markings

above and beyond the regulatory signs and dashed yield line marking?

I'm not so sure.

 

---

 

From:    Scott Ritchie <scott@ROUNDABOUTS.US>

Subject: Re: Yield Line

James:

Field observations, similar to others described herein, identifies a wider

yield line (at least 18 inches in width) and a shorter gap (12 inches)

between stripes is more effective for the dashed yield line stripe at the

ICD. 

The shark's tooth yield markings (triangles) are supplemental to the yield

line for multi-lane roundabout approaches to encourage drivers to stagger

between lanes at multi-lane approaches for improved line of site towards the

left in the circulatory roadway for the outside lane.  These markings are

not considered redundant, are placed perpendicular to the travel way

(straight), and are offset between lanes specifically for an unobstructed

line of sight for the outside lane.  Shark's tooth markings are not needed

at single lane approaches (optional).

Scott 

---

From: Jeff Hillegonds [mailto:hillegonds@PROGRESSIVEAE.COM]

Sent: Wednesday, December 03, 2008 1:44 PM

To: ROUNDABOUTS@LISTSERV.KSU.EDU

Subject: Re: Yield Line

We have also typically used 12" wide dashed line (3' dash - 3' gap) for

our roundabout designs here in west Michigan.

We have not considered wider striping, but I don't know why it wouldn't

work.  It may help with visibility.

Jeffrey A. Hillegonds, P.E.

 

---

From:    Clive Penn Sawers <PENNTRAFF@AOL.COM>

Subject: Re: Yield Line

Andy, I agree. There is no point in having two lines.

In the UK the  line is advisory and we mostly do not use yield signs. In some instances we do  make the yield mandatory by adding the yield signs and adjusting the markings to  the mandatory ones but this is the exception not the rule and very rare on  normal roundabouts. The position of the line represents the edge of the  circulatory roadway and the position at which to yield, hence we call it the  give-way or yield line.

At mini-roundabouts the location of this line is  critical to the satisfactory operation of the layout and it is often NOT on the  circumference of the inscribed circle.

Good to have the various images - take care that vegetation and signs do  not obscure drivers' view of the circulatory roadway; once you have lots of roundabouts and drivers are familiar with them, think about reducing the clutter of unnecessary signs; drivers drive by the layout and remember too that one of  the most important "signs" is the roundabout center itself - drivers will come  to recognise the dome and what it represents. Make sure they can see it clearly from as far back as possible.

Clive Sawers MA MICE  CEng

---

From:    "Kingsbury, Dwight" <Dwight.Kingsbury@DOT.STATE.FL.US>

Subject: Re: Yield Line, edge line, give way line, limit line, shark's teeth, etc.

Typical edge lines are 6" wide, but the MUTCD supports use of a wide edge line ("at least twice the width of a normal line") "for greater emphasis". What the MUTCD calls "dotted" edge lines are also used at driveways, which are also locations where entering drivers are obliged to yield. A 2' dash with a 2' gap, such as shown in the Lansing photo, is a valid "dotted" edge line extension. I certainly agree, though, that an edge line of 18" width would be unusual at driveways (a dotted edge line is supposed to be the same width as the solid edge line it extends).

Given what should be a growing familiarity with such lines, due to the spread of roundabouts, it would not be surprising if many US drivers do now associate these lines with a yielding obligation, even though such lines do not establish the obligation.

I'm not sure I've heard anyone outside the technical community refer to the dashed/dotted white lines at roundabout entrances as "yield lines". Nevertheless, it's obvious that most (US) folks on this list do think of them as yield lines, and I suspect that perception is now shared by many US drivers.

It may well be that marking of official (shark's teeth) yield lines would produce no increased rate of yielding at a roundabout's entrances, especially if the rate were already fairly high. If yielding rates have been unsatisfactory, it's also conceivable that widening the dashed lines could be as effective as adding shark's teeth, or even more so, although offhand I'm not aware of a study that has directly compared the effectiveness of the two treatments.

In any case, if wide dashed lines at roundabout entrances can adequately perform double duty, then shark's teeth would indeed be redundant in this application.

Dwight

---

David's picture from Detroit supports my support for Jim Dunlop's shark

teeth + ICD line practice.  As you can see, the motorist (note I didn't say

van, see Traffic by Tom Vanderbilt) has clearly yielded with the nose of the

minivan in the circulatory lane.  I think we see a lot of folks pull up too

far at intersections across NC, and the sharks teeth yield lines seem to be

working well across the state at all types of intersections.

Example: Ocean Isle Roundabout

http://flickr.com/photos/15530177@N05/2840557155/

Todd B. Delk, PE

---