Memorandum

City of Lawrence

Public Works

 

TO:

David Corliss, City Manager

FROM:

Charles F. Soules, P.E., Director of Public Works

CC:

Diane Stoddard, Casey Toomay, Cynthia Wagner, Mark Thiel, David Cronin, David Woosley, Nick Voss

Date:

April 1, 2014

RE:

Response to Questions from City Commission meeting on November 26, 2014 regarding Project No. PW1341 – Wakarusa Drive, Oread West Drive to just north of Legends Drive and Inverness Drive, Pavement Reconstruction, Geometric Improvements, Sidewalk & Pavement Marking

March 26, 2013 Consent Agenda Item – Set Bid Date of April 9, 2013

 

 

BACKGROUND

At the City Commission on November 26, 2014, a number of comments and questions were raised regarding construction of a roundabout at Wakarusa Drive and Inverness Drive.   Those comments and questions, along with staff responses are provided below. 

 

COMMENT

Nov. 18, 2014 memo: The Insurance Institute for Highway Safety conducted study of 24 intersections before and after roundabout construction. The study shows a 39% decrease in crashes, a 76% decrease in injury crashes, and as much as 90% reduction in fatal or incapacitating injuries.

 

What the Nov. 18 memo failed to report: The information was reported in a bulletin published by the Insurance Institute for Highway Safety, presumably to promote its own interests.2  No information was given to support the findings, the "researchers" were not identified, the nature of the intersections and the roundabouts was not disclosed and no literature source for the information was given.3

 

STAFF RESPONSE

The Insurance Institute for Highway Safety (IIHS) is an independent, nonprofit scientific and educational organization dedicated to reducing the losses — deaths, injuries and property damage — from crashes on the nation's roads.  It is wholly supported by auto insurers and insurance associations.  The data was taken from a monthly publication from the IIHS.  The Researchers were from Ryerson Polytechnic University, the Institute of Highway Safety, and the University of Maine.  The complete study can be found at http://safety.fhwa.dot.gov/intersection/resources/fhwasa09027/resources/Crash%20Reductions%20Following%20Installation%20of%20Roundabouts.pdf.  The methodology, data, and results can all be found in the above report.

 

 

COMMENT

Nov. 18, 2014 memo: In an environmental impact study conducted by the Insurance Institute for Highway Safety shows the amount of vehicle emissions produced by multilane roundabout and a signalized intersection were compared. A roundabout at this location resulted in fuel consumption and carbon dioxide being reduced by 34%. Hydrocarbons, carbon monoxide, and nitrogen oxide were reduced between 40% and 45%.

 

What the Nov. 18 memo failed to report: This was another bulletin published by the Insurance Institute for Highway Safety.4    68% of drivers older than 70 years took an alternative route to avoid the roundabouts,5 1ikely increasing vehicle emissions.  Multiple other findings of the study were not disclosed including the fact that the only statistically-significant finding in crash rates was an increase in the property damage-only crash rate at one roundabout and confusion among drivers about the proper use of roundabouts persisted a year after construction.6

 

STAFF RESPONSE

This was a study published by the IIHS.  During both the before and after period drivers were photographed placed in age categories including one for ages 70 and older.  The study did show a reduction in observed drivers in the 70 and over age category using the roadway after construction of a roundabout.  The study also showed that only 27% of drivers 70 and older favored roundabouts before construction.  After 6 months 51% of the group favored roundabouts and after one year 65% favored the roundabouts.  It should also be noted that while this study indicates a reduction in older drivers using the study route (w/roundabout), AARP (American Association of Retired Persons) has a lot of information that supports roundabouts versus signals and stop signs.

 

Before and after crash data was collected for the two roundabouts in this area. At one of the intersections/roundabout both injury and property damage only crashes both decreased after the roundabout was installed.

 

At the other intersection/roundabout injury accidents decreased but property only accidents increased from 2 crashes in the before period to 4 crashes after construction of the roundabout.

The study did find that fuel consumption and vehicle emissions did decrease.

 

 

COMMENT

Nov. 18, 2014 memo: KDOT and Kansas State University conducted the Operational Performance of Kansas Roundabouts study Eleven Kansas roundabouts including Harvard/ Monterey Way were studied before and after the construction of a roundabout.  In this study average intersection delay went from 20 seconds to 8 seconds and the percent of vehicles stopped went from 58% to 29% (see attached crash history data).

 

What the Nov. 18 memo failed to report: Only 2 of the II roundabouts studied were comparable to the proposed roundabout.  The cited literature was not reviewed.  The finding that large multilane roundabouts (of the type proposed) are not as safe as small and medium capacity roundabouts and the fact that crash reduction was less pronounced for pedestrians, and uncertain for bicyclists were not mentioned in the memo. 7

 

STAFF RESPONSE

The statement referred to is a general statement contained in the abstract of the report: “safety appears to be better at small and medium capacity roundabouts than at large multilane roundabouts. Crash reductions at modern roundabouts are most pronounced for motor vehicles, less pronounced for pedestrians and indefinite for bicyclists, depending on the study and bicycle design treatments”.

 

The proposed roundabout is not a large capacity roundabout.  A large capacity roundabout must have at least one three-lane or four-lane entry.  The proposed roundabout is a medium capacity roundabout with at least one two-lane entry.

The primary objective of the study was not to confirm this statement but to compare the operational performance of roundabouts in Kansas with other traffic control devices.

 

The conclusions were:

·         The modern roundabouts in Kansas operated more efficiently than the before intersection control (AWSC/TWSC/Signal) at all locations studied.

·         There was a (65%) decrease in the Average Intersection Delay (Seconds/Vehicle) for the AM and PM periods combined, in the after condition after the installation of modern roundabout.  The decrease was observed to be statistically significant.

·         There was a (71%) decrease in the Maximum Approach Delay (Seconds/Vehicle) for the AM and PM periods combined, in the after condition after the installation of modern roundabout.  The decrease was observed to be statistically significant.

·         There was a (44%) decrease in the 95% Queue Length (feet) for the AM and PM periods combined, in the after condition after the installation of modern roundabout.  The decrease was observed to be statistically significant. 

·         There was a (53%) decrease in the Degree of Saturation (v/c) for the PM and AM periods combined, in the after condition after the installation of modern roundabout.  The decrease was observed to be statistically significant. 

·         There was a (52%) decrease in the Proportion of Vehicles Stopped (%) for the PM and AM periods combined, in the after condition after the installation of modern roundabout.  The decrease was observed to be statistically significant.

·         There was a (42%) decrease in the Maximum Proportion of Vehicles Stopped (%) for the PM and AM periods combined, in the after condition after the installation of modern roundabout.  The decrease was observed to be statistically significant.

·         Since the reductions in delay, queuing and proportion of vehicles stopped are statistically significant for the after condition of a modern roundabout, the movement of traffic through these intersections i.e., operational efficiency, should be significantly improved.

·         Since all the locations had a range of different traffic conditions, it is reasonable to suggest that a modern roundabout may be the best intersection alternative for several other locations in Kansas with similar ranges of traffic volumes.

·         Further studies should be conducted in other locations in Kansas with different traffic conditions, particularly those where volumes are high enough that a multi-lane roundabout is operating near capacity, in order to get a much clearer picture.

 

 

COMMENT

Nov. 18, 2014 memo: Topeka has two roundabouts with the same lane configuration as the proposed roundabout in Lawrence. The one at 37th & Wanamaker has had two crashes per year before and two crashes per year after the construction of a roundabout. The other one at 46th & Hunters Ridge has had three crashes per year before and three crashes per year after the construction of a roundabout. There have been a total of six injury crashes at these intersections before a roundabout was installed All six of the crashes were right angle crashes.  There have not been any injury crashes after the construction of the roundabouts.

 

What the Nov. 18 memo failed to report: This was a study primarily of one-lane roundabouts. 8 There was a 50% increase in crashes at 37th & Wanamaker9 and a 7%   increase in crashes at 46th & Hunter's Ridge. 10  The number of injury accidents at those two intersections was not reported at all.  Since no statistical analysis was done, the significance of the findings was undetermined. 11

 

STAFF RESPONSE

At the intersection of 37th and Wanamaker there were 8 accidents from 2002 to 2006 (2006 included the construction of the roundabout), 8 crashes in 5 years is 1.6 crashes per year of which 2 were injury accidents. After the construction of the roundabout, from 2007 to 2013 there were 16 crashes.  Therefore, 16 crashes in 7 years is 2.29 crashes per year after the roundabout, with no injuries.

 

At the intersection of 46th and Hunters Ridge there were 17 crashes from 2003 to 2009.  Therefore 17 crashes in 7 years is 2.43 crashes per year of which 3 were injury crashes.  The roundabout was constructed in 2010.  In 2011 there were three crashes.  Data from 2012 and 2013 was not available.  Therefore there were 3 crashes in one year (2011) of which none were injury accidents.   Data from 2012 and 2013 was not available. 

 

 

COMMENT

Nov. 18, 2014 memo: Data was compiled for 18 roundabouts in the City of Lawrence. Over the past three years 18 crashes have been reported at the 18 roundabouts, one of them being in injury crash. The injury crash involved a motorcycle skidding and losing control. The motorcycle rider suffered minor injuries amounting to scrapes and bruises.

 

What the Nov. 18 memo failed to report: All of the roundabouts were one-lane roundabouts. None was comparable to the 2-lane roundabout being proposed 12

 

STAFF RESPONSE

The City of Lawrence has 18 single lane roundabouts.

 

At the City Commission meeting of November 5, 2013 Commissioner Farmer requested crash data at the roundabouts currently in the City of Lawrence.  The memo reported that over the past 3 years 18 crashes have been reported at the 18 roundabouts with only one resulting in an injury.

 

The memo did not fail to report that these roundabouts are single lane.  Staff was providing the Commission with the information that was requested. 

 

Attached is the list of roundabouts in Lawrence.

 

 

COMMENT

Nov. 18, 2014 memo: The city of Golden, Colorado installed four roundabouts along an arterial roadway. The 85th percentile speed was reduced from 47 mph to 33 mph.  A speed study of Wakarusa Drive shows a 85th percentile speed (free-flow traffic typical through a green light at a traffic signal), of 46 mph.  Kasold north of Peterson has an 85th percentile speed of 45 mph mid-block between the roundabouts.

 

What the Nov. 18 memo failed to report: Four roundabouts were placed in a half-mile section of the Golden, Colorado road, at approximately 1/6-mile intervals.   The relevance of this to the proposed two-lane roundabout is uncertain.

 

STAFF RESPONSE

When a roundabout was proposed at Inverness and Wakarusa it was discussed that public works staff would recommend the same intersection control at Wakarusa and Harvard as what would be used at Inverness and Wakarusa.  The roundabouts in Golden, Colorado were discussed to show that roundabouts in a series could slow traffic speeds while decreasing the time it takes to get through a corridor.