Subject: Re: New Report of Interest

Hi Ken:

Believe it was primarily safety--the French have the best comprehensive

highway safety program I've run into--all modes, all aspects, specific

goals/objectives, and periodic evaluation of results.  Makes the U.S.

collection of stovepipes look like a mountain to the French desert.  It is

hard to conceive of another reason to build roundabouts with the costs

involved, other than safety.

The question is best posed to Bernard Guichet for the authoritative answer.

       Tony

From:    "Pain, Richard" <RPAIN@NAS.EDU>

Subject: Speaking of SPFs for Roundabouts

There will be a new NCHRP project this spring on roundabouts: 

Project 17-70  "Roundabout Crash Prediction Method for the Highway Safety Manual".   Shortly NCHRP will be issuing a request for nominations for the project panel who write the RFP, select the winning proposal and provide technical review and oversight throughout the project.  Please watch for an announcement on this list-serv.  By the end of the summer when an RFP is issued we'll make sure it is posted on this list-serv also.  

Rick Pain and Bernardo Kleiner

TRB

202-334-2964

rpain@nas.edu or bkleiner@nas.edu

Subject: New Report of Interest

      Developing Safety Performance Measures for Roundabout Applications in the State of Oregon

The Oregon State Department of Transportation has released a report that documents efforts to quantify the safety performance functions of roundabouts in order to evaluate the safety performance of single-lane, four-leg roundabouts.

Copies available from NTIS, and online at  http://www.oregon.gov/ODOT/TD/TP_RES/

Subject: Re: New Report of Interest

I think I found the specific link:

http://www.oregon.gov/ODOT/TD/TP_RES/docs/Reports/2013/SPR733_Roundabout.pdf

John Burnside, P.E., T.E.

Eugene R(Gene)Russell Sr.,PE, PhD, 

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

Subject: New Report of Interest

The conclusion is on page 63:

"... it is feasible to expect that an increase in exposure may ultimately result in the roundabout SPF converging on the traditional intersection SPF. For the sites studied, however, the safety benefits of the roundabouts are dramatic."  [SPF = Safety Performance Functions]

In short, what the investigators actually found was dramatic safety benefits, but took it upon themselves to recommend caution in construction of 1-lane roundabouts at high volume locations (>30,000 vpd), based on extrapolation of a curve in their Figure 4.11. 

I imagine that if anyone did build a 1-lane roundabout for more than 30K vpd, the result would be slower traffic at peak hours due to congestion and of course, generally speaking slower = safer. At off-peak but busy hours, I imagine the safety level would be comparable to the 1-lane Bird Rock roundabouts at their peak hour; which is to say, quite safe.  At less busy hours I imagine the safety performance would be comparable to the sites the investigators actually studied, where they found "dramatic" safety benefits.  Nowhere in my imagination does the safety performance of a 1-lane roundabout ultimately converge on the traditional intersection safety performance. 

-Ken

Ken Sides, PE

Subject: Re: New Report of Interest

I'd be looking to see if and to where traffic would re-route in considering=

 the safety impacts of a single-lane RAB handling 30K ADT.  It might not be=

 that bad, but the political impacts of such re-routing might be unacceptab=

le, too.

Rick Perez, P.E.

From:    TONY Redington <tonyrvt99@GMAIL.COM>

Subject: Re: New Report of Interest

Ken:

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?  Or wouldn't we be doing benefit/cost

analyses with serious safety dollar factors in all urban highway projects?

 When bicycle interests cannot make a difference it gives you an idea of

how entrenched the car culture really is.  Be glad you are not a rail

passenger advocate!

        Tony

From:    TONY Redington <tonyrvt99@GMAIL.COM>

Subject: Re: New Report of Interest

HI Rick:

With many roadways in slow but steady traffic declines, it is less of a

risk or congestion cost to take intersections in the 30-35,000 daily

entering traffic numbers and build single laners.  Our US 2//302 Montpelier

roundabout (no traffic change in over three decades)  was built with ROW

taken for a second lane--it operated using SIDRA/RODEL analysis just fine

with 29,000 entering vehicles--for decades the number has been and is

22,000 per day with 84 tractor trailers.   Major entry corridors here in

Burlington are running 8-28% down in mainline traffic since about 1990 with

a continued slide since 2000.  Meanwhile the planners believing the Traffic

Growth Elf still project 1% increases annually!  Two and a half decades of

traffic numbers do not a trend history make!  You can always provide for a

second lane in the "future," ditto slip/CTLs--but they should not be

included to start (projects take several years to get on the ground and

traffic can be evaluated nearer to construction).

Finally, note the SPFs you reference do not include the "French Safety

Factor"--another roughly 30% of injury rate gain as more and more

roundabouts are built.

          Tony