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Bikes and Roundabouts

Page history last edited by Frank Broen 10 years, 7 months ago

Gene, Ken and Bob:

 

The performance of roundabouts in regard to bicyclist safety really is

pretty well known, at least for 1-laners, and the basic principles to

follow increasingly become quite clear.

 

1-Laners   The VTI  (Sweden) and Schoon and van Minnen (Netherlands)

studies show anything but a single lane roundabout generates about a 200

percent greater injury rate.  The VTI study "before" numbers translated

into "predicted after" eight injuries (two serious) and "actual after" just

two (both light) injuries.  The Netherlands study was a 60% reduction (or

sign/signal crashes were 250 percent greater than the roundabout).  Note

the Swedish roundabouts sampled had higher diameters than our current urban

practice of about 90-130 feet diameters.

 

But the hidden and just as important secondary findings if you will, in

both these studies involves the data on a pathed configuration before to a

pathed configuration after where crash rates declined in proportions

approaching the safety gain for walkers, i.e., about a 90% reduction in the

Netherlands study--and in the Swedish study the bicyclist crashes at  "no

path before" to "no-path after" roundabouts--that is, the cyclist had to

"take the lane" before and after--were 2 1/2 times higher than "after"

pathed roundabouts injury generation.  This is pretty basic stuff.

 

Thanks to the almost overnight acceptance of cycle track--and the known

need to find an alternative to chaotic signal intersection designs for

bicycle treatments--the pathed roundabout is almost a must-do treatment at

intersections to assure safety and service to all bicyclist skills/ages.

 And, yes, ramping to shared walk/bike movements around a roundabout and

its crossings becomes practically mandatory.

 

2-Laners  Probably the same design principles apply, but the data on safety

gain remains circumstantial.  The best data right now is VTI, but the

roundabouts involved were mostly larger--200 feet in diameter--than current

practice.  As Gene Russell is fond of saying--and I agree here--more

research needed but probably there are some good case studies out there

which can be done quickly.

 

I know from my own experience of "taking the lane" at roundabouts (mostly

single lanes) that choosing pathing, if available, would now probably be

more attractive.  Again, Burlington's first new roundabout on a busy street

includes complete pathing.

 

The hope is that when the bicyclist community begins to see the safety and

service gain of pathed roundabouts in tandem with cycle track, roundabout

development rates will experience a significant increase.

 

               Tony

 


From:    Bob Giordano <mist@STRANS.ORG>

Subject: Roundabout Revolution Could Be Safer for Bikes

 

Yes, it seems well-designed roundabouts- esp. single lane- are much safer for people on bikes than at traffic signals.  We track all bike/car crashes in Missoula, MT (pop. 75k).

 

There are about 4 reported bike/car crashes each week here- and a typical crash cause is 'I did not see the cyclist' as a motorist takes a left at a signal.  There have been no reported bike/car crashes at the five modern roundabouts in Missoula (about 20 'roundabout years').

 

The better safety at roundabouts for cyclists seems to be attributed to slower speeds, all-right movements and eyes on each other.

 

--

Bob Giordano, Director

Free Cycles Missoula

Missoula Institute for Sustainable Transportation www.strans.org, mist@strans.org, 406.880.6834

 

 

Ken Sides wrote:

> The League of American Bicyclists gave Carmel, IN, a bronze for being

bicycle-friendly.

> http://normantranscript.com/headlines/x86510958/Roundabout-revolution-could-be-safer-for-bikes

By the way, Carmel has grown to 81,564 population...and 78 roundabouts.

Rounding off, Carmel has maintained its ratio of 1 roundabout per 1,000

residents.  That's convenient, because it makes it very easy to make the

point to local audiences of how far behind they are from achieving

"roundabout parity" with Carmel.  For example, I showed a slide to an

ASCE/T&DI chapter meeting last week that illustrated Tampa would have to

have 322 roundabouts just to catch up with Carmel.

> -Ken

> Ken Sides, PE

 


Gary:

 

Those involved in transportation deal with a cross section of all users

allowed to use the streets.  For ease of discourse there are two types of

streets, those of moderate speeds--25-40 mph--with lots of cars, bicycles,

and walkers and those; and local streets with few cars, mostly 20-25 mph

speeds or less and easily managed for speed and safety.  High speed

roadways--above 40 mph-are excluded since few walkers and bicycles can be

accommodated in a economic way assuring an acceptable level of safety

except on separate pathways (again, all skill levels).

 

The VTI and Schoon and van Minnen papers both show reduced bicyclist

intersection crash frequency and reduced injury severity (single lane) for

a cross section of skill users prevalent in the Netherlands and Sweden at

the time of the studies.  Both studies pointed to presence of cycle path

context providing a far higher level of crash reductions.   Further, the

introduction of cycle track along with other bicyclist and walker

infrastructure dropped Netherlands kid bicyclist deaths by about 90% (from

over 400 to about 15 a year).  Unfortunately there is not U.S. experience

with bicycle transportation since current infrastructure by its nature does

not serve a cross section of users as does the infrastructure of several

Western Europe and some others worldwide.

 

Of course, the safest environment or all users is shared space--no track,

no lanes---just basically open space with a most surface treatments to

guide users (no signs,no curbs, no signals)--with prevalent speeds under 10

mph with 100% yields by vehicles.

 

It is fair to suggest that those who wish to take lanes rather than tracks

may do so, as local jurisdictions so decide.  Regarding segregation,

segregation of walkers on sidewalks reduces walker crashes by about 90%

(FHWA), and segregation of bicyclists who so choose on cycle track and

pathed roundabouts promises a similar major differential here on the

positive side for cyclists (of all skills).  Clearly "segregation", a

charged word, is not a fair word to use in discussing either walkers or

bicyclists when it comes to safety.  Rather, the proper words are the base

words of transportation analysis: safety, service and capacity.   In the

absence of European studies showing increased frequencies of cyclist

crashes on tracked street segments or the absence of an anticipated higher

safety level when cycle track is paired with roundabout intersection--it

would seem appropriate to follow the European lead in treatments here.

 

                 Tony

 

People,

 

I thought of recent discussions here concerning the integration-segregation

issue that applies to cyclists at roundabouts and elsewhere on our roads

when I read this article recently published by Mighk

Wilson<http://mighkwilson.com/about-mighk/>on the I

Am Traffic website <http://iamtraffic.org>.

 

*China Cups and Butterflies: Options and

Ethics<http://iamtraffic.org/news-views/china-cups-and-butterflies-options-=

and-ethics/>

*

What I find of most interest is Mighk's framing of the issues surrounding

the segregated vs. integrated views of cycling. And the following made me

realize that I am wasting my time trying to convince others with words that

integration is the better way to cycle in most situations:

 

*This bike-lane-versus-integration argument has been running for 30 years

at a stalemate, and statistically speaking it=E2=80=99s unwinnable. The arg=

ument is

in essence: overtaking crashes versus other crashes. The experienced and

trained bicycle driver sees the risk of the overtaking motorist as

exceptionally low and the risks of turning and crossing conflicts as

significantly higher. . . .Advocates of bike lanes, cycle tracks and

sidepaths see the risk of overtaking motorists as unacceptably high and

believe the turning and crossing conflicts that bikeways create can be

mitigated with better design and motorist training and enforcement. They

also tie the tenuous safety benefit of bikeways to the desire to get more

people on bikes, making the equally tenuous

claim<http://injuryprevention.bmj.com/content/9/3/205.abstract> that

getting more people on bikes will reduce the crash rate (but not the crash

numbers). Cyclists who predominantly use edge or pedestrian behavior have

little to no experience with bicycle driving behavior, so they are unable

to compare the effectiveness for themselves.*

 

Because does not deal primarily with roundabouts (although they are

mentioned), I don't think it would be appropriate to discuss the article

and its arguments here. Instead, discussion would better take place of on

the comment section appended to the article.

 

I have appended below extracts from Mighk's article that he highlights.

 

-- Gary

 

Adding more rules will not solve the problem, because adding more rules

adds points of failure. Instead of more rules, cyclists need more options

to avoid the errors of others.

 

For some strange reason, the opinions of the untrained and less experienced

cyclists are held in higher regard than those of the trained and

experienced ones. I know of no other activity in which that is the case.

 

Cyclists who predominantly use edge or pedestrian behavior have little to

no experience with bicycle driving behavior, so they are unable to compare

the effectiveness for themselves.

 

If you cannot predict which risk is greater, then you cannot ethically

restrict a person options for limiting their risk based on their own real

world experience.

 

If you go through a Goal Zero process and ignore the most effective

strategies for reasons like =E2=80=9Cpeople aren=E2=80=99t interested in th=

at=E2=80=9D (a common

argument against expecting people to seek cycling education), you=E2=80=99r=

e really

saying =E2=80=9Ca 40% reduction is good enough.=E2=80=9D

 

Inhibiting people from learning better strategies is also unethical. How

does a novice ever learn to reduce his own risks if training is dismissed

as irrelevant or impractical and the infrastructure discourages the more

successful behavior?

 


Gary:

 

Yes, cultures are different between the U.S. and Canada versus Western

European nations with their flourishing walking and bicycling modes which

enjoy high levels of service and safety--we differ in having lower

standards for licensing, enforcement, transport education--and

infrastructure.  Our concern on this listserv centers on the installation

of the most important element of safe walking and bicycling infrastructure

already well entrenched in Western Europe--the modern roundabout.

 

Regardless of culture, the roundabout as infrastructure brings lot of

benefits ranging from reduced injury and delay to energy conservation.

 And, yes, without getting into a discussion of protected bike lane or lack

thereof, pathed roundabouts also provide a substantial safety benefit to

bicyclists in single lane installations and probably two lane installations

given the bicyclist safety performance found in studies to date.  Whether

or not cycle track along busy arterials and collectors connect now or in

the future, provision of a pathed roundabout can be justified on its own

merits.

 

Guess the questions would be, do you object to roundabout designs which

provide a pathed treatment for bicyclists?  Does not the evidence to date

suggest pathed roundabouts provide--taking into consideration all skill

levels--a safer bicyclist treatment?  And, finally, doesn't the RIG2

suggestion of on/off ramps for bicyclists suggest the safety benefit of the

alternative to taking the travel lane?

 

 

               Tony

 


<sigh>   At the joint invitation of several agencies in Tallahassee, I gave=

 a 2-hour luncheon presentation there several years ago.  I emphasized low-=

speed and compact design until I was blue in the face.   Sometimes "round" =

is the only part of the message that sticks...

 

-Ken

Ken Sides, PE

 

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

f Michael Wallwork

Sent: Wednesday, June 19, 2013 1:06 PM

To: ROUNDABOUTS@LISTSERV.KSU.EDU

Subject: Re: Designing for Bicycles

 

The Tallahassee Roundabout is overly large with a central island of 137 fee=

t diameter, splitter islands that could be better shaped and the incorrect =

bicycle design. However, in this case, only competent bicyclists are likely=

 to use the roundabout and hence it is less of a problem. But as developmen=

t occurs and the range of bicyclists increase then it could be problematic.

 

 

Michael Wallwork, PE

Alternate Street Design, P.A.

904 710-2150

 


 

Hmm, should I have saved the Tallahassee example for the roundabouts geomet=

ric design roast? To return to the point about markings I was trying to mak=

e, let's consider examples from the Melbourne metro area of Victoria, Austr=

alia, depicted in the report for VicRoads, "Evaluation of Shared Lane Marki=

ngs for Cyclists" (http://cyclingresourcecentre.org.au/images/uploads/post/=

attachment/0012_VicRoads_Sharrows_(Final-2).pdf).

 

See Figures 1.3 (p 4), 3.2 (p 15), and 3.3 (p 16). In these examples, the S=

LMs were placed, not in the (single-lane) roundabout, but on the approach l=

ane. This placement actually makes more sense than that in the Tallahassee =

example because, if a cyclist who stays on the roadway hasn't occupied a ce=

ntral lane position before entering a roundabout, the cyclist hasn't convey=

ed the message they need to to overtaking drivers and it may well be too la=

te to try to control the lane in the circulatory roadway if a motorist is o=

vertaking.

 

Dwight Kingsbury

 


 

Gary:

 

More on including paths for bicycles at roundabouts...

 

Leaving separate paths/cycle track for street segments, consider only how

the immediate approach and movements of bicycles need to be designed for

maximum safety for all bicyclist populations (read kids, old folks, and

those who say "I do not feel safe riding in the street so I only bike on

sidewalks").

 

Again, the Schoon and van Minnen research guides us in this area.  Their

study clearly shows that:

(1) in the typical US situation going from a no-path before to a path

treatment at the intersection, a reduction of 100% in moped/cycl injuries

(8 locations).

(2)  going from a before intersection with a path to a path in the

roundabout, 89% reduction in moped/cycle injuries (51 locations).

 

In the best known element of the study, going from path condition "before"

to a "no lane" for the bicyclist in the roundabout, a 35% increase in

injuries (3 cases).   And going from lane to lane or path to lane 4-6%

decrease in injuries (70 cases)--this suggests that lanes do have value at

non-roundabout intersections but add little safety at roundabouts.

 However, lanes generally---with or without a roundabout--tend to exclude

less skilled bicycle populations.

 

So, even if there immediate plans do not exist for cycle track/paths along

one or more legs street-sections, scoping and design needs to incorporate a

pathway through the roundabout for bicyclists in an urban context over and

above on-off ramps. Such designs do immediately provide for a reduction in

bicycle casualty rates.   Or at a very minimum provide for further possible

future retrofit.

 

              Tony

 


 

Ken,

 

Thanks for posting the bicycle videos, Gary -- very interesting!  I hadn't

> seen anything like it before.

 

>From the design and operation perspective, the Florida video<https://vimeo.com/60224468>is interesting. I think the cyclists'

movements into the inside lane and

back again going straight is just due to cyclists' looking for the shortest distance. But the gore at 2:05 was a surprise and this looks like a design flaw to me.

 

-- Gary

 


From:    "Batson, Scott" <Scott.Batson@PORTLANDOREGON.GOV>

Subject: Re: Roundabouts and bicycles

 

Design flaw is a bit strong.  It appears to be meant as a spiral out striping design poorly executed.  It shouldn't have the bump, but taper out gently from the inside to the outside lane.

It may just be an optical illusion (or old markings?) they look good from the air

http://tinyurl.com/cdhyumx

 

- Scott Batson 

 


Subject: Roundabouts and bicycles

 

Tony,

 

You wrote:

 

Unfortunately--AAA brave policy study notwithstanding---safety is not a

> major concern in the urban highway transportation arena.  Otherwise,

> wouldn't we be building roundabouts at the U.S. equivalent of the

> French

> 1993-2003 rate, 12,000-15,000 a year rate versus our actual 400-500 a

> year rate now?  Ditto for bicycle safety in regard to cycle track/bike

> pathway routes on major urban roadways?

 

 

I think we all recognize that the safety benefits of roundabouts are primarily due to the elimination of all the crossing conflicts that are present in rectangular intersections. In contrast, cycle tracks or bike paths along roadways *add* crossing conflicts at all driveways and intersections.  I would hope that roundabout engineers, planners and advocates see that this is a safety disadvantage.

 

The roundabout corridor on La Jolla Boulevard was mentioned in this thread.

Here is a 4-minute video <https://vimeo.com/61988764> of navigating these on bicycle that I took last March. Here is another 2-minute video<https://vimeo.com/60224468>of senior tandemists navigating a series of multi-lane roundabouts in The Villages, FL (near Orlando). Notice how easily bicycle drivers can integrate with motorized traffic in roundabouts given the low speeds and absence of crossing conflicts. Compare this with the manufactured conflicts of the segregated design<http://www.bbc.co.uk/news/uk-england-london-22347184>being

considered for London.

 

I don't want to start a discussion of the larger issues related to segregating bicycle  traffic from motorized traffic as it is not a relevant topic for this list if it doesn't involve roundabout locations. I recommend that anyone interested in this topic visit the new  I Am Traffic<http://iamtraffic.org/> website, particularly the engineering section<http://iamtraffic.org/category/engineering/> which contains an article on "Bicyclist Behaviors and Crash Risk<http://iamtraffic.org/2012/12/behaviors-and-risk/>

."

  

-- Gary

 

 


Subject: Re: Roundabouts and bicycles

 

Gary,

 

I see the issue differently.  Crossing conflicts still occur at modern roundabouts, for pedestrians, and these conflicts can be mitigated by other means, both physical and institutional.  I believe the best designed modern roundabout accommodates all levels of cyclist, 8-80 is the current buzzword.  The confident cyclist can take the lane and operate comfortably in the 15-20 mph flow of traffic.  Those less confident can use side paths and shared use areas to go around the outside with pedestrians.

 

The problems that come up are primarily related to designs that don't sufficiently slow motorists and drivers that don't want to slow down, or cannot comprehend the potential consequences of their poor choices.  Some of these choices and desires are based on our profession's historical actions to accommodate high speed roadways.  Many cannot yet comprehend that slowing down for a modern roundabout results in less overall delay. We equate efficiency with speed.

 

Slow operation of motorists at all points within a modern roundabout, including the exits, is a key element to achieve high safety for all users of the modern roundabout.  Institutionally, a change in the mindset of motorists that they always have the right of way, and always should - everywhere, will take longer to achieve.  The institutional mindset change will, I believe, have the greater impact on the safety of all road users.

 

Cyclist traveling around the outside of the modern roundabout need to be separated from the circular roadway at least a car length so that they are visible to exiting motorists, minimizing the right-hook type of collisions common at standard intersections with bike lanes.  Slow speeds of cyclists are important as well.  The Dutch seem to understand how to make this feature work, or at least have adopted the mind-set that non-motorized traffic always has the right of way.

http://www.youtube.com/watch?v=wEXD0guLQY0

 

The Dutch Institute for Road Safety Research,[35] however, noted that "roundabouts with separate bicycle tracks have a much lower number of casualties per roundabout than roundabouts with bicycle lanes, van Minnen (1995)". van Minnen advised for separated bicycle tracks, but against bicycle lanes for roundabouts.

 

- Scott Batson

 


Subject: Re: Bicycle Roundabout

 

Google Streetview image (from 2009) of the traffic circle before

reconstruction: http://goo.gl/maps/HuwzC . It did resemble a (very large) roundabout, but was actually a traffic circle inasmuch as it was controlled by signals at the path crossings on the legs and traffic circulating in the circle had to yield (behind the sharks' teeth yield lines visible in the Streetview and aerial imagery) to entering traffic. The diameter of the circle was about 350 ft--larger than the 300 ft upper limit of the inscribed circle diameter range for multilane roundabouts described in the Roundabouts Informational Guide.

 

No lane markings were used in the old traffic circle, which was wide enough to accommodate three lines of traffic. According to German Wikipedia ( http://de.wikipedia.org/wiki/Hovenring ), longitudinal markings were intentionally omitted so as to prompt drivers to reduce speed; however, many drivers experienced the design as "unpleasant".

 

Signal control required storage space for stopping vehicles on exit legs, hence the considerable setbacks of the path crossings.

 

Dwight Kingsbury


From:    mrwahlstedt@TRANSYSTEMS.COM

Subject: Bicycle Roundabout

 

I recently came across an article about an elevated roundabout the Dutch have built just for bicycles.  Very impressive looking! Bike ADT is 5,000, vehicles 25,000.

http://bicycledutch.wordpress.com/2012/08/23/spectacular-new-floating-cycle-roundabout/

 

Interestingly, they removed a vehicular roundabout at the location and replaced it with a signalized intersection.

 

 

Mike R. Wahlstedt, PE, PTOE

Master Professional/Vice President

Traffic Service Line Leader

 


Subject: CARS NO!, SAFETY AND ROUNDABOUTS YES!

The American myth of the car as "normal" amounts to just that--a myth.  After two years in San Francisco's North

Beach and now in Montreal the only "value" of the passenger car comes in the form of the danger it presents at urban

intersections without roundabouts.  Simply, car ownership in a well designed urban space makes as much sense as

carrying a tennis racquet to a football game.  Bicycles comprise the majority of global passenger vehicles, and about a

third of European nations urban trips are bike/ped.  Efforts begun in the 1990s by the Netherlands and Germany to

foster bike/ped urban networks resulted in higher bike/ped modal shares.

Unfortunately bicycle advocates center their efforts on share the road rather than pushing equally for the most

important form of transportation--walking--urban change, i.e., the roundabout which benefits all modes. 

Pedestrians, of course, except for local streets exert very little influence on urban transportation, and government

funds concentrate on car-oriented investment, explaining in great part why roundabouts growth occurs at such a

glacial pace in North America.

Roundabouts instead of being a minor subcommittee in ITE and gasping for even a study or two at TRB really rate the

research and promotion status of the car, the trolley, and the roadway itself.  

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

>From    : Ken Sides[mailto:Ken.Sides@myclearwater.com]

Sent    : 10/28/2008 6:50:15 AM

To      : ROUNDABOUTS@listserv.ksu.edu

Cc      :

Subject : RE: Intersection safety science: France, Australia, USA, and UK - Drivers

 In the United States, if you can't drive you can't have a life, due to the almost total absence of modal choice.  So we

ought not be too quick to blame the older folks for continuing to drive -- everyone wants to have a life. 

-Ken


Subject: Re: Bicycle safety in roundabouts studies?

CalTrans has funded a study about bicyclists and pedestrians at roundabouts. It is being conducted by UC Berkeley and Alta Planning + Design. I’m likely going to be involved at some stage with this research, but I have not been yet. There are no results to report as of yet, but at least this needed research is being conducted to some degree. The study will look at both safety and operations as I understand it. Hopefully it will provide some useful data on bicycle safety at roundabouts.

-Michael

Michael M. Moule, PE, PTOE


> Good day all,

> Just wondering if there have been any studies done over the past few

> years in the US specifically regarding bicycle safety in and around

> roundabouts.  NCHRP 572 didn't seem to have much information on bicycle

> crash rates - I'm guessing due to sample size.  We've found some

> studies from Europe that raise concerns with some of our bicycling

> constituents, but these studies didn't go into enough detail with

> roundabout specifics (multi-lane vs. single lane; separate bike path

> vs. none; striped bike lane vs. having bike act as vehicle; etc.).

> Have any states done studies on this issue?

>

> Thanks!

> Ken

>

> Ken E. Johnson, P.E.

> South Metro Area Engineer, Dakota County

> Mn/DOT Metropolitan District - Program Delivery

> 1500 West County Road B-2

> Roseville, MN  55113

> Office: 651-234-7718

> Fax: 651-234-7608

> ken.johnson@dot.state.mn.us

------------------------------

Date:    Thu, 30 Oct 2008 11:28:40 -0400

From:    Ken Sides <Ken.Sides@MYCLEARWATER.COM>

Subject: Bicycle safety in roundabouts studies?

I certainly hope so.  I watch bicyclists safely and comfortably transit low-speed modern roundabouts and wonder what the fuss is all about, as I see them cruise along in step with slow-moving motorized traffic, blessedly free of motorists who are turning one way but looking quite another. 


Subject: Re: Bicycle safety in roundabouts studies?

There is continuing controversy about the use of detectable warnings on bike ramps at roundabouts (if provided, yes).  It is our view that, in a properly designed, single-lane roundabout, bike ramps are not needed; cyclists should simply join the traffic flow.  There may be an issue with multi-lane roundabouts where vehicle speeds may be higher due to cutting across lanes. 

Dennis Cannon


From:    Andrew O'Brien <andrew@OBRIENTRAFFIC.COM>

Subject: Re: Bicycle safety in roundabouts studies?

Weekend before last, I was one of about 16,000

cyclists who rode in Melbourne's Round-the-Bay

event - all of the route is on arterial roads and

freeway.  I rode 120km of the 210km complete

journey (I'm only half mad)  - and rode  through

17 roundabouts (6 2-lane rbts incl) and maybe

40 sets of traffic signals.  It was far easier

and safer riding through the rbts, particularly

when bunches of cyclists were involved.  You

should try being in a bunch of about 40 cyclists

in the centre of the road doing a filter turn on

the inter-green - it gets pretty exciting!

http://www.bv.com.au/great-rides/20005/

Andy


Subject: Re: Bicycle safety in roundabouts studies?

The statement in the paper of Daniels et al. that "construction of a roundabout generally raises the number of severe injury crashes with bicyclists, regardless of the design type of cycle facilities" is not so conclusive as this partial quotation may suggest.

The complete statement was that "The results for the study sample suggest" this conclusion. As the authors discussed in their "Results" section, none of the increased (raw data) rates of fatal/serious injury crashes at roundabouts of any of the four types considered (mixed traffic, cycle lanes, separate cycle paths, and grade-separated) was significant at the 95% confidence level; only the aggregate results (for all 90 roundabouts) were significant and yielded a best estimate for the change in the severe injury crash rate of about 42%. The confidence interval was apparently large enough, though, to include a no-change result.

More caveats

1. Daniels et al. considered not just crashes that involved cyclist injuries, but any injury-causing crash that involved at least one cyclist. Presumably, most of the injured parties were cyclists, although this is not stated.

2. With respect to location, all bicycle-related injury crashes that occurred at each roundabout were included, as well as all those that occurred between the roundabout and the nearest hectometer pole on each leg were included. Thus, as the authors state, the effects they studied were effects on bicycle crash rates >at or near< roundabouts, not just at roundabouts.

3. The applicability of the results to US applications is somewhat limited, as only 9 of the 90 Flemish roundabouts were of the mixed-traffic design commonly used in the US; 40 (44%) of the roundabouts included cycle lanes, and these had the worst after-period results with respect to cyclist injuries of all severity levels (they were the only subgroup in which the injury rate increase was found to be significant at the 95% confidence level); in the US, marking of bicycle lanes in roundabouts is expressly prohibited by the MUTCD.

83 of the 90 roundabouts were single-lane; the other seven were double-lane.

Dwight Kingsbury


Subject: Re: Los Alamitos Traffic Circle, Long Beach, California

Note that the "regular" sized two lane roundabout where there is significant bicycle traffic would likely be 140 to 180 in diameter while the

Long Beach circle conversion to a roundabout is about 470 feet in diameter.  A any roundabout where bicycles and pedestrians are

permitted, then a ramp off for bicyclists who feel uncomfortable with the roundabout needs to be provided.  My own experience with the 2-

laner at the Brattleboro, VT roundabout (172 feet in diameter) is that under heavy traffic it is not comfortable in my case, a "street bicyclist,"

so I sometimes switch to ped mode through the intersection. 

 


Here is a video that coincidentally just arrived from a Caltrans 

source.  I don't feel comfortable copying the whole message, but have 

included the link to the video:   http://www.cyclistview.com/innertube/longbeachtrafficcircle.htm 

     The message said the video showed how safe a bicycle can navigate 

a roundabout.  Personally, I don't think this location looks very 

safe.  The bicycle is traveling 10 to 20 mph while the cars are 

traveling close to 30, and there are no stripes, just wide-open asphalt.

Aside from the bicycle, you can get a good idea of what this huge 

roundabout looks like.  The first two passes come from the SE through 

the four-lane entry--see the two lanes flare to four before the YIELD 

line.  The third pass comes from the west and has a three-lane flared 

entry and a bypass separated by a "banana" island.  This entry is on a 

7% downgrade, hence the 20 mph entry speed of the bicyclist.

John Burnside, P.E.

Consulting Traffic Engineer


Subject: Re: Los Alamitos Traffic Circle, Long Beach, California

I see nothing for a competent cyclist to be alarmed about. Our two-lane roundabout in Tallahassee isn't this big, nor is the beach entry roundabout in Clearwater, but aside from that I would rate the conditions shown in this video as "everyday"/"normal"/"nothing objectionable"/"dive right in" by the standards of my (16 years of) commuter cycling experience on urban main roads in Florida.

In the one-and-a-half-loop pass done at 20 mph, it appeared that only two motorists passed the two cyclists in the circulatory roadway.

In their two-loop pass at 10-11 mph, several motorists did pass the cyclists, but I saw nothing alarming about the passes.

The cyclists wisely kept away from the edges. Most bicycle-MV crashes in roundabouts have involved entering or exiting motorists who did not yield to cyclists who were continuing past exits. Similar "right hook" and "motorist looked but did not see" bicycle-MV crashes occur at signalized intersections, and the behavioral countermeasures are similar: ride in a "lane" (marked or not) appropriate for one's destination, taking care, on any approach to a turn-off where one intends not to turn off, to keep away from the outside edge (turn-off path) so as to avoid giving motorists a misleading impression (or not being seen by them).

The February 2006 story in the LA Times implies that, since the redesign in 1993, there had been only one fatal crash in the Los Alamitos Traffic Circle.

Dwight


On Wed, Feb 16, 2011 at 10:38, Peter Furth <pfurth@coe.neu.edu> wrote:

Sorry, I feel compelled to give a long answer to Joe's question. The short

answer comes at the end.

 

I really dislike the "more confident / less confident cyclist" dichotomy

that pervades the roundabout-bicycle topic. I just finished reading the new

NCHRP Informational Guide on Roundabouts, which repeats that theme again &

again. The problem is that "confident" is a loose enough term that could

refer to the top 5% of the population (in terms of confidence of riding with

traffic) or the top 80%. A term that vague becomes a convenient device for

escaping the real responsibility of providing for the mainstream population.

 

[Adding to my discomfort with the Guide's paradigm for accommodating

different users is that it repeats at least 4 times that on-road cyclists

typically ride between 12 and 20 mph. On paths, where a more mainstream

population rides without the stress of traffic, average speed for adults is

11 mph. Somehow, the Guide's understanding of speed dismisses 50% or more of

the mainstream population.]

 

The roundabout guide recommends bicycling in the roadway as the default,

with a backup being that "less confident" cyclists can ride in the sidewalk,

facilitated by "escape ramps" connecting a bike lane on the approach to the

sidewalk. However, "ramps should not normally be used at urban one-lane

roundabouts" (p. 6-72). On one-lane urban roundabouts, we're all supposed to

be confident enough to take the lane.

 

And where built, these ramps are not supposed to be direct and inviting.

"Bike ramps should not be placed directly in line with the bike lane or

otherwise placed in a manner that appears to the cyclists that the bike ramp

and the sidewalk is the recommended path of travel through the roundabout.

This encourages more sidewalk use by bicyclists, which can have a negative

effect on pedestrians and may be less safe for bicyclists as well" (p.

6-73). Here you have it:  cyclists are supposed to be recommended to ride in

the road, regardless of traffic volume or number of lanes. To discourage

cyclists from ramping to the sidewalk, ramps should not be provided at urban

one-lane roundabouts; and where provided, they are supposed to be at an

angle of 35 to 45 degrees to the bike lane, forcing the cyclists to slow to

to make a sharp swerve.

 

Contrast three situations. One, a single-lane roundabout with relatively

light traffic -- say, 6,000 veh/ day -- and a tight enough radius that cars

in the roundabout go under 20 mph. Here, riding in a roundabout is like

riding in a local street, with slow traffic that has plenty of gaps. Nearly

all cyclists will do that comfortably; while there is no authoritative

figure for that, I'll throw out 80% as a plausible value. That's why the

Dutch guide says riding in the roundabout is OK for traffic up to 8,000 per

day. Those who aren't comfortable in such a roundabout probably also aren't

comfortable riding in the local streets approaching this roundabout. They'll

approach it on the sidewalk, and stay on the sidewalk as they ride around.

Fine; we have a design that serves everybody.

 

Case 2: the urban single lane roundabout with 20,000 cars per day. (The

Guide's limit for single lane is 25,000.) Volumes on the approach road(s)

will be 10,000 veh/day or more, on which most people will be uncomfortable

riding in the street unless they have a bike lane. So let's assume the

approach road(s) have a bike lane. The Guide says to end the bike lane lane

on the approach, squeezing down the entry to force cyclists to take the lane

on the approach. The fraction of bicyclists "confident" enough to take the

lane on a road with 10,000 veh/day is probably under 5%. So now, the same

brush that painted us a design that serves almost everybody has painted

another that leaves the majority unserved.

 

Case 3: the multilane roundabout with escape ramps to the sidewalk. The

"recommended path" is to stay in the road. The fraction of cyclists

"confident" enough to do that is probably under 2%. The rest get a

second-class, "we really don't want you to use the sidewalk but will

grudgingly allow it" treatment.

 

All of this fuzziness comes from failing to define the bicyclist "user" as a

mainstream, composite bicyclist who wants a path that is convenient and

quick, while at the same time providing adequate separation from motor

traffic. Yes, you can have both, as they do in Holland. Instead, we've got

this dichotomy:  make the default design for confident cyclists and provide

a workaround for the less confident.

 

Now, to address Joe's question about sharrows in a roundabout:  IMO, it

sounds like a good idea for a single lane roundabout with under 8,000

vehicles per day. With that light a volume, bicycling in the roundabout is

acceptable to most cyclists, and so using sharrows to declare that "cyclists

are expected to use the road" makes sense. It will encourage cyclists to not

feel wrong or overly aggressive about taking the lane and blocking cars that

are behind them.

 

And, IMO, it's a terrible idea to use them on roundabouts with more than

8,000 veh/day, or with multilane roundabouts. That would create a conflict

between the overt recommendation of the road authority and what the

mainstream population considers acceptable.

 

However, in order to give guidance such as this. one would be setting a

volume threshold for when riding in a roundabout is the recommended path for

cyclists, and that's something that, so far, the engineering establishment

hasn't been willing to do. So I'm afraid that guidance about SLM's in

roundabouts will be used to put them into multilane roundabouts and into

single lane roundabouts with high traffic volumes. I'd rather see SLM's in

no roundabout than to see them used to publicly declare that cyclists are

expected to use a facility that doesn't meet the needs of mainstream

cyclists.

 

Peter Furth

 

> On 2/7/2011 12:17 PM, Joe Gilpin wrote:

>> Greetings all,

>> 

>> To continue the discussion of roundabouts, has anyone ever used a Shared

>> Lane Marking in a single or multi-lane roundabout? I know that the City of

>> San Francisco mentions this as an application of SLMs, but I don't know of

>> a

>> single jurisdiction that has actually tried it.

>> 

>> It seems to me that it could help direct more confident cyclists to

>> position

>> themselves more properly within a roundabout and that it would probably

>> work

>> best in lower speed single lane roundabouts with a lot of deflection.

>> Bicycle escape ramps from bike lanes and using pedestrian crossings would

>> probably remain the preferred choice of less confident cyclists.

>> 

>> It also strikes me that installing SLMs in a roundabout could be a lot of

>> work to maintain as vehicle tires would be turning and creating more wear

>> on

>> the pavement markings. It may be difficult to keep them visible.

>> 

>> Thoughts?

>> *Joe Gilpin

>> Associate*

>> *Alta Planning + Design

>> transportation | recreation | innovation

>> 406-624-6117

>> www.altaplanning.com*

 

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