Horizontal/Subsurface Infrastructure & Transportation

This might be more of a driver's ed question, but I figured some traffic engineers could have some insight on this issue.  How is a driver supposed to use turn signals (or as we call them in Rhode Island, "blinkas") when entering and exiting a traffic circle (or as we call them in RI, rotaries)? 

When entering a traffic circle, my instinct is to turn on my left turn signal, just like merging onto a highway, and yet action of entering can resemble turning right.  This presents the problem of using the turn signal to exit and quickly change it to the right side.  All of this could work quite well for a large diameter traffic circle, but becomes more of an issue as the diameter gets smaller.  The smaller the diameter, the faster the exits pass by and there is little time to turn use your blinka.  Too soon and you are giving false signals, too late, why bother?  Add to the matter that the turn signal tends to disengage automatically when turning in the opposite direction, double lane rotaries where you might want to pass, or just paying attention to driving rather than being concerned about using your turn signals... is it just a distraction to yourself and others?

What is the rule?  Does the public know the rule?  Does anyone abide by it?  If they did, would it just lead to more confusion or less?

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Chad Morrison P.E., M.ASCE
Professional Engineer
Greenville RI
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Hi Chad, I've struggled with this also.  I'd like to use my turn signal to aid others but, as you mentioned, there's often not enough time and I feel that I need my full focus to be on watching and reacting to traffic.  I drive through Carmel, IN, often, which has the most roundabouts of any city in the US, and over this past year they had an advertising campaign trying to encourage drivers to signal when exiting.  In interviews with news stations and newspapers articles they mentioned they would be stepping up enforcement.  They passed a law or 2 that helped specifically clarify how you are supposed to signal and would allow them to write enforceable tickets.  I haven't seen any police staking out roundabouts or pulling over anyone near roundabouts, though.  The takeaway for me was that they felt it would be most helpful to try to get people in the habit of signaling their exit.  That would be helpful to people queued, waiting to merge into the roundabout, which I will agree can be a difficult, and quick, last-minute decision when you are waiting to see if the vehicle coming around is going to exit or continue around.  I've tried to get in the habit of signaling my exit and it is very hard.  The ergonomics of how cars are designed don't lend themselves to turning through a roundabout and flipping the signal lever, and the timing has to be perfect, as you mentioned, so that the turn isn't signaled too early, making it more confusing for other drivers.  After trying it some I gave up because I found it more confusing to other drivers than helpful.

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Ben Browning P.E., M.ASCE
Carmel IN
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I have never used my turn signal in a roundabout, but have wondered about it before.  I think what keeps me from bothering to do so is that I feel it isn't even visible to the person who wants to know if I am staying in the roundabout or leaving.  The driver most likely interesting in knowing what I am doing is going to be to the left and ahead of my vehicle (waiting on the outside of the roundabout), but the blinker I would be turning on is on the right side of my vehicle.  Can they even see the blinker if I turn it on?​

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Nancy Streu EIT, A.M.ASCE
Civil Engineer
Muscatine Power & Water
Muscatine IA
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The drivers waiting to enter a roundabout can see the blinker on the front of your car as you approach. And they will appreciate being made aware of your intentions.

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Andy Kennedy P.E., M.ASCE
Charlotte, NC
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Original Message:
Sent: 01-17-2020 09:10
From: Nancy Streu
Subject: Use of Turn Signals in Traffic Circles

I have never used my turn signal in a roundabout, but have wondered about it before.  I think what keeps me from bothering to do so is that I feel it isn't even visible to the person who wants to know if I am staying in the roundabout or leaving.  The driver most likely interesting in knowing what I am doing is going to be to the left and ahead of my vehicle (waiting on the outside of the roundabout), but the blinker I would be turning on is on the right side of my vehicle.  Can they even see the blinker if I turn it on?​

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Nancy Streu EIT, A.M.ASCE
Civil Engineer
Muscatine Power & Water
Muscatine IA
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It's a good question, and one that likely varies from state to state.

Here's a rather amusing, but well written, article that may help a bit:
https://www.thenewstribune.com/news/local/traffic/article134773799.html

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Eric Pilcher P.E., M.ASCE
Bonney Lake, WA
eric.pilcher@...
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Being from Massachusetts, we are similar in driving habits.  My own experience has been no signal entering a rotary.  When exiting a rotary, I use my turn signals to let drivers behind me know I am exiting.  It also let's traffic entering at my exit know I am leaving rotary.

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Timothy Stinson P.E., M.ASCE
PRIN ENG RETIRE
Holbrook MA
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Original Message:
Sent: 01-17-2020 12:18
From: Eric Pilcher
Subject: Use of Turn Signals in Traffic Circles

It's a good question, and one that likely varies from state to state.

Here's a rather amusing, but well written, article that may help a bit:
https://www.thenewstribune.com/news/local/traffic/article134773799.html

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Eric Pilcher P.E., M.ASCE
Bonney Lake, WA
<maskemail>eric.pilcher@...</maskemail>
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Chad, that's a problem her in Texas, too.  But I agree with no signal on entering (where else can one go?) but a right turn signal as soon as I'm at or just past the last exit before mine.  From my experience, a signal does help!

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James Justin Mercier, P.E., CFM
Life Member ASCE
Sr. Life Member IEEE
Austin Texas
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The United States was such a nice place to immigrate to when there were no traffic circles or "roundabouts" here. Now they have become fashionable, and architects and city planners just love them.

On large "roundabouts" in Europe I have seen turn  signals used to indicate the driver is nearing his exit and needs an opening in the outside lane.
Make sure your signal cancels after you make your exit turn.

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Hans H. Coucheron-Aamot
Albuquerque NM
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I always use my signal on roundabouts.  Anything to help other drivers know your intent will make driving safer & more efficient.  In NJ we are replacing circles with roundabouts, designed to current standards.  We in NJ have many decades of experience with the old and now the new design.  For a one-lane roundabout I use right-turn signal for entry, because it's the first move the car makes (steering wheel turned to the right).  Once in the roundabout I immediately switch to my left-turn signal to indicate I'm "staying in" or circulating the roundabout (left-turn of the steering wheel required for all roundabouts in the USA).  Prior to exiting the roundabout I will use my right-turn signal, imediately after the approach before the one I plan to exit to.  The left-turn signal for staying-in is important to let those entering know that I'm not exiting so don't enter. (Those within the roundabout have priority, those entering must yield).  The right-turn signal for exiting notifies anyone wishing to enter from that approach will get a gap by my leaving.  Advance notice that a gap will become available is especially important for larger vehicles that require more time to enter from stop. A stream of 2 or 3 vehicles properly using their signals can give the required gap to a tractor trailer. Using turn signals makes a roundabout, especially a busy one, safer and more efficient.  With very low volume roundabouts turn signals are probably not as necessary. Set a good turn signal habit and stick with it.  Note: The use of turn signals indicated above is significantly more complicated for two or three-lane roundabouts because once within the roundabout the signal could have multiple meanings, such as switching lanes within the roundabout. Being in the outside lane and using the right-turn signal to exit is a courtesy to help traffic enter more safely and efficiently.

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A Feranda P.E., M.ASCE
Senior Project Manager
Shamong NJ
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In the central US, roundabouts are far to small to use turn signals effectively, so it does not make any sense to do so.  You are in and out so quickly, it would just confuse other drivers as to what exactly you are doing, which makes it less effective.​  The use of the right turn signal when entering is completely silly, as you have no other choice on how to enter the roundabout.  I can see the use of the right turn signal upon exiting if it is a large enough roundabout, and there is time for the driver ahead waiting to enter to see your signal.

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Mark Justice P.E., M.ASCE
Transportation Engineer III
Blacklick OH
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Original Message:
Sent: 01-20-2020 01:02
From: A Feranda
Subject: Use of Turn Signals in Traffic Circles

I always use my signal on roundabouts.  Anything to help other drivers know your intent will make driving safer & more efficient.  In NJ we are replacing circles with roundabouts, designed to current standards.  We in NJ have many decades of experience with the old and now the new design.  For a one-lane roundabout I use right-turn signal for entry, because it's the first move the car makes (steering wheel turned to the right).  Once in the roundabout I immediately switch to my left-turn signal to indicate I'm "staying in" or circulating the roundabout (left-turn of the steering wheel required for all roundabouts in the USA).  Prior to exiting the roundabout I will use my right-turn signal, imediately after the approach before the one I plan to exit to.  The left-turn signal for staying-in is important to let those entering know that I'm not exiting so don't enter. (Those within the roundabout have priority, those entering must yield).  The right-turn signal for exiting notifies anyone wishing to enter from that approach will get a gap by my leaving.  Advance notice that a gap will become available is especially important for larger vehicles that require more time to enter from stop. A stream of 2 or 3 vehicles properly using their signals can give the required gap to a tractor trailer. Using turn signals makes a roundabout, especially a busy one, safer and more efficient.  With very low volume roundabouts turn signals are probably not as necessary. Set a good turn signal habit and stick with it.  Note: The use of turn signals indicated above is significantly more complicated for two or three-lane roundabouts because once within the roundabout the signal could have multiple meanings, such as switching lanes within the roundabout. Being in the outside lane and using the right-turn signal to exit is a courtesy to help traffic enter more safely and efficiently.

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A Feranda P.E., M.ASCE
Senior Project Manager
Shamong NJ
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I believe it is important to use turn signals for traffic circles and roundabouts.
For one-lane roundabouts left blinker indicates continuing past the next exit point, right blinker indicates leaving at the next exit point.
It's always appropriate to use blinkers to let other drivers know your intentions. Remember, it's safer for everyone when we use our blinkers to indicate intentions, for us and our passengers as well the for the other vehicle. And it also helps others to make quicker decisions and keep traffic flowing better for everyone.

For multi-lane roundabouts it gets a little trickier but the idea is the same. The link that Eric Pitcher posted has a good video explanation.

In NC the planners seem to love roundabouts and are placing them everywhere. I've been using this method of signaling for a couple of years and from what I've observed the traffic entering the circle typically understands my intentions and reacts appropriately and more quickly than when no signal is given. I confess, sometimes I fail to signal. After all, what good is a hypothesis without testing the alternatives?

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Andy Kennedy P.E., M.ASCE
Charlotte, NC
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Being from Boston, we use our "blinkas" when entering a circle. Most circles are 2 lanes wide, so if you are going say 3/4's around circle, as soon as you enter circle you use your left blinka to signal to get on inside track.  The outside track os for getting on and off the circle. When about 1/2 way around after you pass the next to last exit you put your right blinka on to move into outer circle, leep on the blinka and get off the circle at the 3/4 point.  Real simple.

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Dennis Doherty P.E., F.ASCE
National Practice Leader - Trenchless Technologies
Haley & Aldrich
Nashua NH
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My son is in medical school in Boston and I can honestly say NOBODY EVER USES their so-called 'blinkas' there!  The Uber drivers there are also the worst I've encountered anywhere I've traveled across the U.S. and place their 18-foot autos into 10-foot or less openings while running at road speed.  It's also pretty much one speed there -- WIDE OPEN.  But I do agree that blinka use would make for considerable improvement!

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Thomas Brantley P.E., M.ASCE
Chief of Building Engineering
Tallahassee FL
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Original Message:
Sent: 01-21-2020 08:22
From: Dennis Doherty
Subject: Use of Turn Signals in Traffic Circles

Being from Boston, we use our "blinkas" when entering a circle. Most circles are 2 lanes wide, so if you are going say 3/4's around circle, as soon as you enter circle you use your left blinka to signal to get on inside track.  The outside track os for getting on and off the circle. When about 1/2 way around after you pass the next to last exit you put your right blinka on to move into outer circle, leep on the blinka and get off the circle at the 3/4 point.  Real simple.

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Dennis Doherty P.E., F.ASCE
National Practice Leader - Trenchless Technologies
Haley & Aldrich
Nashua NH
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First things first with regards to some of the replies from those living in the New England area (I'm originally from the North Shore region of Massachusetts).  Rotaries and even the mostly-long-gone traffic circles that used to be all over New Jersey typically have a larger diameter than the roundabouts that have recently been planned/built in the US.  That said & having grown up with rotaries; the general premise was to use turn signals after one's entered the rotary to either change lanes within or to exit NOT prior to entering.  The reason being is that the entrances to the rotaries/circles are essentially merge-style ramps that only allow for one-way movement. 

HOWEVER & obviously, if the related rotary/circle and has entrance ramps with more than one lane and one wishes to change lanes (where allowed) prior to entering the circle; then, yes one must use their turn-signal.

It's worth noting that several existing rotaries in Massachusetts have recently been restriped to multi-lane roundabout specs per the MUTCD.  The noticeable change is increased advance signage regarding which lane to be in prior to entering the rotary with regards to route & destination and more channelized lane striping upon entering & exiting the rotary.  In some instances, the exit ramps from these rotaries are striped as either two lanes or two lanes spaced further apart via cross-hatched striping.  Such separates traffic that just entered the rotary wanting to exit at the next immediate ramp to simply from the inside-rotary traffic.

Regarding recent smaller roundabouts that have been built in the Bay State; such seems to operate in a similar manner as the legacy rotary but on a smaller size & scale.  With these & per the original question; one only needs to signal while in or to exit the roundabout but not (except for lane changes if any) upon entering since it's is a merge-style ramp.

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Christopher Commans P.E., M.ASCE
Urban Engineers, Inc.
Philadelphia PA
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Thank all for the great (if somewhat befuddled) answers!  I think the consensus is to only use your turn signal when exiting the traffic circle or changing lanes.  There seems to also be some agreement that smaller circles may not require their use.  Finally, most drivers to no seem to be aware or mindful of the rule.  As we are all not heading back to driver's ed anytime soon, how do we get the message out?  Something as simple as a DOT campaign or signage?  Certainly if police intend to enforce the law, there needs to be some compliance from the public.  While maybe not quite at the same level of concern, it could be modeled after campaigns when new cell phone laws being enacted.

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Chad Morrison P.E., M.ASCE
Professional Engineer
Greenville RI
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Original Message:
Sent: 01-22-2020 08:49
From: Christopher Commans
Subject: Use of Turn Signals in Traffic Circles

First things first with regards to some of the replies from those living in the New England area (I'm originally from the North Shore region of Massachusetts).  Rotaries and even the mostly-long-gone traffic circles that used to be all over New Jersey typically have a larger diameter than the roundabouts that have recently been planned/built in the US.  That said & having grown up with rotaries; the general premise was to use turn signals after one's entered the rotary to either change lanes within or to exit NOT prior to entering.  The reason being is that the entrances to the rotaries/circles are essentially merge-style ramps that only allow for one-way movement. 

HOWEVER & obviously, if the related rotary/circle and has entrance ramps with more than one lane and one wishes to change lanes (where allowed) prior to entering the circle; then, yes one must use their turn-signal.

It's worth noting that several existing rotaries in Massachusetts have recently been restriped to multi-lane roundabout specs per the MUTCD.  The noticeable change is increased advance signage regarding which lane to be in prior to entering the rotary with regards to route & destination and more channelized lane striping upon entering & exiting the rotary.  In some instances, the exit ramps from these rotaries are striped as either two lanes or two lanes spaced further apart via cross-hatched striping.  Such separates traffic that just entered the rotary wanting to exit at the next immediate ramp to simply from the inside-rotary traffic.

Regarding recent smaller roundabouts that have been built in the Bay State; such seems to operate in a similar manner as the legacy rotary but on a smaller size & scale.  With these & per the original question; one only needs to signal while in or to exit the roundabout but not (except for lane changes if any) upon entering since it's is a merge-style ramp.

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Christopher Commans P.E., M.ASCE
Urban Engineers, Inc.
Philadelphia PA
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Hello Chad
As I understand the law in the state of Washington, whenever a driver moves into or out of a lane, he/she must signal the direction of the turn.  The law apparently does not specifically address traffic circles but by definition, it applies.  Yes, the public is largely aware of the law but not as it applies to traffic circles.  From my observation, drivers are very good at signalling on roads and streets but not in or through traffic circles.

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Leon Lindbloom P.E., F.ASCE
Richland WA
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Professional Traffic Operations Engineer (PTOE) here!

The name "turn signal" implies that you are signaling your intentions to other drivers on the roadway. There is only one way to enter a roundabout in the USA . Since everyone must circulate in a counterclockwise manner, I don't think it is necessary to use a turn signal to enter the roundabout. 

Once in the roundabout, the signal would be most helpful if turned on when approaching the leg where you intend to exit. The purpose behind using said turn signal would be to signal the driver at the next entry point that you intend to exit, which would allow them to make a more informed decision about when to enter the roundabout.

If you are in a multilane roundabout, you should not be changing lanes!! Last year I attended a roundabout class taught by one of the engineers who wrote most of the guidelines on roundabouts (Rodegerts). During the class, we were told that multilane roundabouts should be designed so that you make lane changes prior to entry. Once you enter the roundabout, you should not need to change lanes in order to exit at your desired location (assuming that you entered in the correct lane).

I believe I saw a comment about using a left turn signal to indicate that you are staying in the roundabout, but I think that will just confuse drivers. Signals are used to indicate that you intend to change lanes - either by turning onto an entirely different roadway, or by shifting into an adjacent travel lane. We do not signal other drivers that we intend to stay in a particular travel lane when on a straight section of roadway, or when negotiating a curve. It is expected that you will stay in your travel lane - until you signal otherwise. 

Personally, if I saw a driver with their left turn signal on in a roundabout, I would assume they don't know what they are doing - because there are no left turn exits. And, if it is a multilane roundabout, they should not be changing lanes.

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Kelly Farabee P.E., M.ASCE
Guyton GA
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In Missouri, the Driver's Guide (Chapter 4, under the heading "Exiting the roundabout", link below) states to "Use your right turn signal to let others know you are exiting".  

It's nuanced in light of others' comments, but rather than leaving your left turn signal on while IN the roundabout, NO signal would indicate your intent to remain in the roundabout.  I'll agree that having the left turn signal on decreases a bit of confusion, but it might be simpler to only indicate your intent to exit the roundabout.

In practice, no one signals any turn. ¯\_(ツ)_/¯

https://dor.mo.gov/pdf/Chapter4.pdf

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Kensey Russell P.E., M.ASCE
HNTB
Oklahoma City OK
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------Original Message------

In Missouri, the Driver's Guide (Chapter 4, under the heading "Exiting the roundabout", link below) states to "Use your right turn signal to let others know you are exiting".  

It's nuanced in light of others' comments, but rather than leaving your left turn signal on while IN the roundabout, NO signal would indicate your intent to remain in the roundabout.  I'll agree that having the left turn signal on decreases a bit of confusion, but it might be simpler to only indicate your intent to exit the roundabout.

In practice, no one signals any turn. ¯\_(ツ)_/¯

https://dor.mo.gov/pdf/Chapter4.pdf

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Kensey Russell P.E., M.ASCE
HNTB
Oklahoma City OK
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Here in Northern California, it seems that many, perhaps most, drivers don't use their turn signals at all, nevermind in traffic circles. One puts oneself in harm's way whenever leaving the house.

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Denis O'Malley P.E., M.ASCE
Principal
Denis M. O'Malley, PE, PMP
Concord CA
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Original Message:
Sent: 02-11-2020 23:21
From: Rodolfo Contreras
Subject: Use of Turn Signals in Traffic Circles

Nothing is better than a little bit of humor into the discussion!

Rodolfo J Contreras

CA EIT 1973

Original Message------

In Missouri, the Driver's Guide (Chapter 4, under the heading "Exiting the roundabout", link below) states to "Use your right turn signal to let others know you are exiting".

It's nuanced in light of others' comments, but rather than leaving your left turn signal on while IN the roundabout, NO signal would indicate your intent to remain in the roundabout.  I'll agree that having the left turn signal on decreases a bit of confusion, but it might be simpler to only indicate your intent to exit the roundabout.

In practice, no one signals any turn. ¯\_(ツ)_/¯

https://dor.mo.gov/pdf/Chapter4.pdf

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Kensey Russell P.E., M.ASCE
HNTB
Oklahoma City OK
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My standard blurb on the question:

Signaling your exit from a roundabout is required in many states, though some states have more general rules about 'signaling your path'.  Signaling left until you're ready to exit will also help motorists not jump in front as you go around (etiquette).  I think the confusion stems from rules about when to signal and distance in advance of an intersection.  I've read law enforcement opinions that depend on each leg of a modern roundabout being a separate intersection, and that is incorrect.  The roundabout is a single intersection and the roundabout is part of the traffic control for that intersection.  Just like any other intersection, drivers should signal their intended path in advance of arrival, right or left, with the added rule about signaling your exit from the circular roadway that many states have specifically adopted.

At the 20 mph operating speed of a roundabout, signalling is quite easy.  I use my signal in advance of entry if turning right or left, and just past the splitter island just before my exit.

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Scott Batson P.E., M.ASCE
Engineer
Portland Bureau of Transportation
Portland OR
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