Memorandum

City of Lawrence

Public Works Department

TO:	Charles Soules, Public Works Director
FROM:	Nicholas Voss
CC:	Mark Thiel, David Cronin
Date:	November 18, 2013
RE:	Project PW1341: Intersection control at Wakarusa Drive & Legends Drive/Inverness Drive

Please include the following item on the City Commission Consent Agenda for consideration at the November 26, 2013 meeting.

Project Description

Wakarusa Drive is proposed to be reconstructed next year as a 2014 Capitol Improvement Project.  Construction limits include north of Oread West Drive, where 2013 construction ended, through the intersection of Legends/Inverness Drive.  This section of Wakarusa has high rutting, localized areas of raveling, base failures, and significant curb & gutter deterioration.  City staff is proposing this section of Wakarusa Drive be reconstructed with 10" concrete on a flyash treated base with a two way left turn lane, curb & gutter, storm sewer, bike lanes, & sidewalk on each side of the roadway. 

Wakarusa & Legends/Inverness Drive

Options for intersection control were discussed at the November 5th commission meeting.  At that time a decision for intersection control was deferred and additional information was requested.  Information requested included the speeds of traffic on Wakarusa Drive, accident data from similar roundabout configurations in Topeka and Kansas City, and accident data for the roundabouts currently in Lawrence.

Roundabout Safety

Roundabouts have substantially fewer conflict points with other vehicles and pedestrians.  They greatly reduce high severity conflicts such as right angle and left-turn/head-on crashes.  They lower driving speeds allowing drivers more time to react to potential conflicts and at lower speeds, drivers are much more likely to yield, or stop if necessary, for other motorists and pedestrians.  Lower speeds also reduce crash severity and pedestrian injury chances.

Roundabout Studies

The Insurance Institute for Highway Safety conducted a 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.

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%.

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).

As the City continues to repair /replace Wakarusa north through Harvard and up to 6^th Street, coordination of signals will have a 2-2.5 minute cycle to provide sufficient time for vehicles to clear the intersection.

Roundabout Crash Data

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.

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.

Speed Studies

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 a 85th percentile speed of 45 mph mid-block between the roundabouts.

Complete Streets

Complete streets are designed and operated to enable safe access for all users, including pedestrians, bicyclists, motorists, and transit riders of all ages and abilities.  The proposed roundabout would efficiently move traffic while slowing it down making the roads safer for vehicles, pedestrians, and bicycles.  It would offer bicyclists the opportunity to use the roundabout as a vehicle or to exit the bike lanes and use their bike as a pedestrian.  In addition, landscaping inside of a roundabout can add to the community feel and can make the intersection more welcoming to everyone.

With a roundabout pedestrians would have to cross a maximum of two lanes of traffic at a time as opposed to five on Wakarusa and pedestrians would only have to cross one direction of traffic at a time as opposed to two on Legends/ Inverness.

AARP also notes in their Brief on Complete Streets, “Half of all older driver deaths occur at intersections. Roads can be engineered for slower speeds through changes to curb radii, lane widths, or replacement of typical intersections with roundabouts.”

Project Cost/Funding

The estimated cost of a roundabout is $350,000, while the estimated cost of a traffic signal is $500,000, plus an annual maintenance cost of at least $5,000 for the intersection ($125,000 over the 20-year life of a traffic signal).  Plans are being designed in house by city staff. 

The estimated total project cost is $2,350,000 and will be funded by infrastructure sales tax.

Project Schedule

Design Plans: Winter 2013

Advertise and Bid: Spring 2014

Construction: Summer/Fall 2014

Action Request

Pending city commission discussion, proceed with project design on Wakarusa Drive PW1341 and receive city commission recommendation on intersection improvements to Wakarusa Drive, Inverness/Legends Drive.

Attachments

Lawrence Roundabout Accident Data

Power Point Presentation