From:  Mark Lenters <Mark.Lenters@GHD.COM> Subject: Re: Principles

In all this dialogue there's a significant oversight on our part - that of the pedestrian's role. It's disappointing that as an industry we have over looked the role of pedestrian assertiveness in seeking physical and device oriented solutions. Agencies like Fort Lauderdale provide assertiveness training to pedestrians for crossing at traffic signals. Check out their brochure! Waterloo Region Canada uses the same training for roundabouts, but they appear to be the only entities seeing the value of a more alert and assertive pedestrian. Check out their Roundabout Dance video!

 

This endless dialogue should be a clue to us that the proliferation of more devices, including signals does not guarantee improved driver response or safe passage in a crosswalk. Worse yet is the false perception factor that more devices instill in the pedestrian coaxed by the use of the device to think the crossing will be safer. A crossing is not safe until the driver stops, no matter how many devices we add. Changing roundabout exit geometry isn't the only answer. Adding traffic signals, flashers, bumps, humps et c. isn't the only answer either.

 

Check Bastian Schroeder's research on the effects of pedestrian assertiveness, not to be confused with NCHRP research on more devices. Also, when field tests of various devices were undertaken by NCHRP, I understand that subject pedestrians were not given a baseline coaching or encouraged to behave assertively. That should be a big clue to us that we're only focusing on the driver behavior side of the problem. No-one, except Waterloo has tested the effects of improved pedestrian assertiveness. In their study driver responsiveness increased from 40% to 100%. Even if it was observed at 90% compliance, that is an impressive result.

What we need is a paradigm shift to the safety of pedestrians, trading off our penchant for unimpeded mobility, like Europe. Those things take time, but in the interim, surely we could be exploring every side of this issue, including training pedestrians. Places like Jackson WY us the flags for pedestrians to hold as they cross. Fort Lauderdale encourages point to seek a gap, then point while crossing; same in Waterloo (see their roundabout dance video). Nothing too sophisticated or device oriented, just a balanced approach on the way to a new paradigm. A bit of enforcement goes a long way too; and, it might be cost-effective.

I watched the MN ped delay study video where peds are waiting at the Richfield roundabout cross-walk for minutes on end. That's no surprise if they didn't signal to the drivers that they intend to cross. Yet from this we have notions that more devices will solve the problem. What happened to the 3-E's triangle of balanced traffic management? Forgive me for feeling ashamed to be part of this industry of more devices.

 

Mark Lenters

 

From: Roundabout Research [mailto:ROUNDABOUTS@LISTSERV.KSU.EDU] On Behalf O f TONY Redington Sent: Tuesday, December 10, 2013 8:38 AM To: ROUNDABOUTS@LISTSERV.KSU.EDU Subject: Re: Principles

 

Hi Mark and all:

Believe your reference Mark is excellent. From my observation as a policy wonk who dabbles in review of technical aspects of roundabout design, the roundabout first and foremost on average cuts (single laner only reliable re search to date) walker injury and fatality rates by about 90% over the past types of interactions. Ditto, probably, based on Dutch data, for bicyclist injury reduction where pathing is provided (again we are talking about single lanes here). So, as a practical matter, one has reduced the risk on average about 90% by putting in the roundabout based on past accepted practices (or more specifically the performance of those roundabouts built in the past). So at the very most we are dealing with a range of 90-100 percent when pursuing further reductions.  Signs, raised crosswalks, etc. work on the margins, a portion of the 10% if you will. Cost and benefit needs to f it in here at some point. Definitely finding the most effective signing makes sense--this is a low cost factor Raised crosswalks make sense with a h igh level of walker volumes--we have just installed a low level raised crosswalk, a mid-block treatment which enters the Marketplace plaza which results in a lot of yielding even though a signal with quick walk-cycle start is available. The impact of a low level textured surface raised crosswalk im pact on speed and yielding is quite impressive.

         Tony

 

 

Hi Mark and all:

Finally you get to a key metric--benefits and costs! This underlies most all of traffic engineering practice and needs to be kept in mind. To an extent our discussion to this point is inside baseball--without doubt roundabouts produce, all factors considered, the biggest bang for the buck in practically all cases compared to the alternatives (not to be mentioned).  The relative superiority of the roundabout is the reason it is "roundabouts fir st" in an increasing number of jurisdictions with NY State DOT being the first in 2005.

 

When one gets to the issue of exit speeds, then the first question to ask i s are what are the costs and benefits from one design approach versus another?  And, is the overall goal--in the case compared to the overall benefit of the roundabout in the first place. But, clearly, these small differentials are large within the context of roundabout design! And the answer will arise from current and future research--meanwhile the realm of individual "good engineering judgement" prevails.  My own non-engineer bias prefers lower speeds in an urban context (if the costs are not unreasonable).

 

       Tony

 

 

On Fri, Dec 6, 2013 at 9:50 AM, Mark Lenters <Mark.Lenters@ghd.com<mailto:M ark.Lenters@ghd.com>> wrote:

I think that there's an important aspect of safety and risk that should be restated. I offer this from our esteemed Canadian colleagues who practice road safety assessments (Hildebrand and Forbes)

 

The appropriate and industry-accepted metric for "risk of loss" in a road safety analysis is collision occurrence and severity (collectively known as "collision risk"). This includes motor vehicle collisions, pedestrian trip and falls, cyclist spills, etc. Safety is not defined by a user's perception of safety, feeling of safety, or convenience of use. In the case of a rural arterial road or a freeway, motor vehicle collision risk is the dominant measure of safety. In urban areas, the collision risk must also be considerate of pedestrians, cyclists, and other road users.

 

Having stated the above, satisfying warrants and other justification criteria for road elements and devices is still used as a secondary metric of safety. This is because conformance with warrants and other criteria provide consistency and uniformity in the application of devices and dimensions, accommodate driver expectancies, and these factors generally enhance safety.

 

Should design attend to the margin, 85%ile and above? If so, we need to alter our road standards to eliminate risk at the margin, but I don't think that society is prepared to adapt to those changes, nor can we afford them at present. I don't disagree that designs should be more sensitive to pedestrians with the example of exit design. I think that we as a design community are becoming more responsive or this exchange wouldn't taking place.

 

My point was that prudent design is context sensitive to reduce, not eliminate, risk of collisions for all users accounting for trade-offs of capacity where context permits it.

 

Mark Lenters

Service Group Manager To: ROUNDABOUTS@LISTSERV.KSU.EDU<mailto:ROUNDABOUTS@LISTSERV.KSU.EDU> Subject: Principles

 

I should mention one last lesson from traffic calming practice that might cross over to roundabouts. In practice, the 85%ile bar and other old-timey metrics are in effect used to deny many residents the relief they seek from illegally speeding vehicles and aggressive driving behavior which is degrading the quality of their home life. In essence, the traffic engineers say s "According to our instruments, you don't have a real problem but rather a perceived problem, and because there is no real problem we aren't going to do anything to help you."

 

We could fall into a similar trap in responding to requests for roundabouts if we are overly literal about adhering to some arbitrary metric and don't take into account the full context of the request and the intersection sit e. Avoiding that trap would mean taking seriously many non-quantitative factors.

 

-Ken

Ken Sides, PE

 

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

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

Sent: Thursday, December 05, 2013 9:58 PM

To: ROUNDABOUTS@LISTSERV.KSU.EDU<mailto:ROUNDABOUTS@LISTSERV.KSU.EDU>

Subject: Principles

 

Well, let's go back to first principles: what are we trying to accomplish here? Like roundabouts, traffic calming was a departure from traditional traffic engineering practice and so there may be some useful similarities.

 

When residents complain about speeding and aggressive driving, many engineers immediately convert that in their minds to a complaint about the 85% speed and so they go measure that. Remember the old saw about everything looking like a nail if all you've got is a hammer. But that wasn't the complaint. The complaints are excessive speeds for a place where they are raising children and oldsters are taking their daily walks. I've had several residents tell me they won't let their kids play in the front yard -- even in upscale neighborhoods with rather nice front yards -- let alone walk or bike across the neighborhood to play. Their sleep is interrupted at night and it stresses them out and hurts their quality of life. We couldn't measure fear and aggressive driving and stolen childhoods with our little boxes with hoses attached.

 

So, what is it we are we trying to accomplish? We're trying to satisfy the residents -- that's the sole reason most retrofit traffic calming programs exist. We tried offering a possible solution (speed humps) to streets where owners of 65% of the properties signed a petition asking for them, on the theory that that would be solid evidence they really wanted speed humps.  Can you imagine getting 65% consensus on anything? Yet many streets obtained the signatures within a few days. One the humps went in, the complaint s ended, there was almost no backlash, and so we figured the traffic calming project must be working.

 

I wasn't trying to determine whether a street "needs to be calmed." I was trying to determine whether the folks living and raising families and growing old on that street truly want speed humps, and the supermajority petition bar tells me that.

 

So, instead of spending time and money conducting studies to measure something nobody has complained about, I would just hand over a petition form and go back to whatever it was I was doing. Should the petition come back some day with enough signatures on it, then I'd put in the humps. No studies, no consultants, no public meetings. No trying to explain to frightened parents why an arbitrary figure was going to determine whether their street was going to be made livable.

 

Similarly, there many be many roundabouts going in now and even more in the future not because of some study the engineers performed, but because someone asked for the roundabout or asked for a solution to a problem a roundabout would solve. Those someones might be developers, politicians, schools, church, businesspersons, residents, environmentalists, artists, sculpture s historians, garden clubs, bicyclists, outdoor exercise enthusiasts, emergency responders, public health officials or citizen advocates. I say we should be open to hearing these requests.

 

Roundabouts can do so much more than simply slow traffic, reduce crashes sharply, reduce injury severity dramatically, virtually eliminate fatalities, eliminate queues, reduce greenhouse gases and restore mobility and freedom to children and oldsters. The motivation may be to create a public space that is safe, pleasant, quiet and suitable for siting landscaping and public art. Or for siting an identity structure to recognize a neighborhood, development, business district, school or famous personage -- the Europeans k now all about this. For 50 years U.S. streets weren't about creating great public spaces but now they can be again.

 

-Ken Sides, PE Norman Garrick [norman.garrick@GMAIL.COM<ma ilto:norman.garrick@GMAIL.COM>]

Sent: Thursday, December 05, 2013 4:52 PM

To: ROUNDABOUTS@LISTSERV.KSU.EDU<mailto:ROUNDABOUTS@LISTSERV.KSU.EDU>

Subject: Re: Principles

 

Thanks Ken

 

In general, I agree in general with your view point on most of these issues . However, I think in general the 85th speed is a useful tool for characterizing the speed profile on a given street segment both to assess an existing site to see if it needs to be traffic calmed or to assess if a traffic calming project is working.

 

Cheers

 

Norman

 

 

On Wed, Dec 4, 2013 at 4:14 PM, Ken Sides <Ken.Sides@myclearwater.com<mailt o:Ken.Sides@myclearwater.com<mailto:Ken.Sides@myclearwater.com%3cmailto:Ken .Sides@myclearwater.com>>> wrote:

 

Sorry if I wasn't clear, Norman. The point I was attempting to make was that the old traditional metrics that have served the traffic profession in t he past may not necessarily be the right metrics for future situations. In the case of the 85%ile speed value, if our thinking stops at that metric w e could in some situations think we've addressed a problem when we actually haven't because that metric doesn't adequately and fully characterize what is important about the case at hand.

 

Average speed, 85%ile speed and volume may be sufficient to characterize some highways and some arterials, but not necessarily everything in the traffic universe.

 

Another example: "LOS" is code for "Level of Service for people in motorized vehicles," but left out is any hint of level of service for folks not in motorized vehicles. Those folks simply don't exist in the LOS metric.

 

Yet a chunk of the population is too young to drive and another chunk is past it's driving prime, plus folks who can't or don't want to drive, and you've got almost a third of the population that has been "disappeared" from the traditional engineering metric of LOS. So the constrained metrics and limited, exclusionary language of the profession has limited our thinking an d therefore the excellence of our engineering design.

 

But with the ongoing development of low-speed modern roundabouts, we have a bright new opportunity to design for everyone. Roundabouts offer so much to so many population groups, and can substantially enhance so many intersection contexts, that this is a really exciting opportunity we should make t he most of.

 

I built on Mark's example of traffic calming to illustrate my point. For m ore on my thoughts on that subject, attached is an ITE paper I gave in California back in 2000 (attached).

 

-Ken

Ken Sides, PE

 

I'm glad Mark mentioned the 85%ile drivers in regard to traffic calming, b t sorry he felt the need to qualify need with "perception of," because that language is often used by traffic engineers (not Mark!) as if the public' s expressed needs weren't real but rather a hallucination or other type of psychological phenomena. Can you picture being in sales and telling your customers that they are just imagining things? Not the path to success.

 

Instead, I offer the alternate explanation that the average speed and the 85%ile speed are inappropriate metrics for characterizing traffic calming problems. No resident has ever asked me to please do something about the 85%ile drivers on their street. Instead, they talk about the speeders. They also talk about the speeding SUV that flipped into a neighbors yard last year or the dog that got hit two years ago two blocks away. The very deep fear is that that pet could just as easily been their child. Yet we don't measure any of those things. Remember GIGO.

 

So if the traditional traffic metrics are inappropriate for traffic calming , why are we still using them? Because we always have. But metrics developed long ago for completely different purposes don't necessarily apply to novel challenges. Such as low-speed modern roundabout design.

 

-Ken

Ken Sides, PE

Mark,

 

I liked your use of the terminology "the influence area of roundabouts (entry and exit)".

 

Very well written and executed.

 

Bill Baranowski,

Michael Wallwork

Sent: Tuesday, December 03, 2013 7:39 AM

To: ROUNDABOUTS@LISTSERV.KSU.EDU<mailto:ROUNDABOUTS@LISTSERV.KSU.EDU<mailto :ROUNDABOUTS@LISTSERV.KSU.EDU%3cmailto:ROUNDABOUTS@LISTSERV.KSU.EDU>>

Subject: Re: Guidelines v Requirements

 

In relation to exit speeds from offset left and on-center designed roundabouts.

 

The reason for the exit speed being lower than the predicted speed at on-center roundabouts is simple. Well-designed on-center design roundabout have smaller R2 due to the smaller R3 than at an Off-set left roundabout which h as a higher R2 due to the flat R3.

 

Also the predicted exit speeds are based on the formula in NCHRP 672 that uses the 85th percentile acceleration rate. But that rate only applies to 85 percent of drivers. The worse drivers are the 15 percentile. They are the ones who typically cause the most problems, hit the curb on the exit exit, etc. These drivers accelerate at a higher rate and hence achieve higher exit speeds. As the exit radius becomes flatter the predicted exit speed increases dramatically compared to the significant limitation due to a "small" R 3 at an on-center roundabout. The benefit to pedestrians is this "small" R3 is significant.

 

Michael Wallwork, PE