1 4 4 - - Lane to 3 Lane to 3 - - Lane Lane Conversions Conversions Tom Welch, P.E. Tom Welch, P.E. State Traffic Safety Engineer State Traffic Safety Engineer Office of Traffic and Safety Office of Traffic and Safety Iowa Department of Transportation Iowa Department of Transportation [email protected][email protected]
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4-Lane to 3-Lane Conversions - Iowa Department of ... Diet.pdf · 4-Lane to 3-Lane Conversions Troy A. Jerman, P.E. Senior Transportation Engineer Office of Traffic and Safety Highway
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44--Lane to 3Lane to 3--Lane Lane ConversionsConversions
Tom Welch, P.E.Tom Welch, P.E.State Traffic Safety EngineerState Traffic Safety EngineerOffice of Traffic and SafetyOffice of Traffic and Safety
Iowa Department of TransportationIowa Department of [email protected]@dot.iowa.gov
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The Iowa 4 Lane to 3 The Iowa 4 Lane to 3 Lane ExperienceLane Experience
Before
After
Optimization of Pavement to Improve Safety Optimization of Pavement to Improve Safety and Enhance Quality of Lifeand Enhance Quality of Life
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Traditional Improvement to 2Traditional Improvement to 2--Lane Urban Street Lane Urban Street
44--Lane Undivided RoadwayLane Undivided Roadway
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USUS--61 Ft. Madison, Iowa61 Ft. Madison, IowaTwoTwo--Lane to FourLane to Four--Lane WideningLane Widening
Excessive speedingExcessive speedingDifficulty entering and crossing USDifficulty entering and crossing US--7575Fatal and major injury older person pedestrian crashes
25 MPH
Fatal and major injury older person pedestrian crashes
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Sioux Center AfterSioux Center After
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Before / After AnalysisBefore / After Analysis
USUS--75 Sioux Center75 Sioux CenterBeforeBefore After After (2)(2) DifferenceDifference
1. Posted Speed Limit – 25MPH 2. 7 months before and after
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Before / After Public Opinion SurveyBefore / After Public Opinion Survey(1) (1)
USUS--75 Sioux Center 75 Sioux Center
BeforeBefore AfterAfter
Support Support ConversionConversion
18 %18 % 45%45%
NeutralNeutral 37 %37 % 15%15%
Oppose Oppose ConversionConversion
45 %45 % 40%40%
(1) 930 Responses- City Population 6,002
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ArdithArdith LeinLein, Executive Director, Executive DirectorSioux Center Chamber of CommerceSioux Center Chamber of Commerce
Mrs. Mrs. LeinLein stated that:stated that:
The Chamber of Commerce Executive Board, as well as The Chamber of Commerce Executive Board, as well as almost all business owners, prefer the threealmost all business owners, prefer the three--lane highway lane highway to the previous fourto the previous four--lane highway.lane highway.
It has slowed traffic down through the central business districtIt has slowed traffic down through the central business district, , which has improved the shopping environment.which has improved the shopping environment.
Pedestrian crossing of USPedestrian crossing of US--75 are much safer; there have been 75 are much safer; there have been fewer accidents and the emergency vehicles like having the centefewer accidents and the emergency vehicles like having the center r lane available to drive in.lane available to drive in.
““Safety has to be the prioritySafety has to be the priority |over a little extra delay.|over a little extra delay.””
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Harold Harold SchieboutSchiebout, City Manager, City Manager““But we can not have it both ways so we have to But we can not have it both ways so we have to decide which is best overall.decide which is best overall.””
““Currently, the city council supports keeping the Currently, the city council supports keeping the conversion permanent.conversion permanent.””
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Resident, Rod Resident, Rod DeKruyfDeKruyf
Rod Rod DeKruytDeKruyt, had called Mr. , had called Mr. SchieboutSchiebout and and stated: stated:
““I thought all of you were plumb nuts when you proposed I thought all of you were plumb nuts when you proposed changing US 75 from 4 lanes to 3 lanes.changing US 75 from 4 lanes to 3 lanes.““But now I take my hat off to you for being persistent.But now I take my hat off to you for being persistent.””““It is not perfect, but it is much better.It is not perfect, but it is much better.””
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Paul Adkins, Chief of PolicePaul Adkins, Chief of Police
Chief Adkins admitted he was opposed to the four lane to three Chief Adkins admitted he was opposed to the four lane to three lane conversion when it was proposed. lane conversion when it was proposed.
He said it was initially confusing for many elderly drivers, butHe said it was initially confusing for many elderly drivers, butnow he is the biggest advocate. now he is the biggest advocate.
He suggested that any city that is considering a conversion to cHe suggested that any city that is considering a conversion to call all him at him at ((------) ) ------ --------
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Blue Grass Blue Grass -- US 61 (9,000 ADT)US 61 (9,000 ADT)Speeds regulated much betterSpeeds regulated much betterAccidents have decreased Accidents have decreased significantlysignificantlyReduction in capacity is not Reduction in capacity is not an issue.an issue.
Sanford Sanford RemlyRemly, Public Works Director, Public Works Director
Osceola Osceola -- US 34 (11,000ADT)US 34 (11,000ADT)““I was skeptical but have since I was skeptical but have since changed my mind.changed my mind.””Initial reactions are positiveInitial reactions are positiveCapacity has not been Capacity has not been adversely affectedadversely affectedOverall a successOverall a success
Brad Wright, City Administrator
Osceola
Brad Wright, City Administrator
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IOWA 4-LANE TO 3-LANE CONVERSION STUDYSUMMARY OF STUDY RESULTS
"Before" cases based on 5 years of data (except Storm Lake); "after" cases based on 1 to 5 years of data. Year of conversion is not included in the data analysis. Storm Lake "before" data 1991 and 1992 only; conversion in 1993. Clear Lake conversion completed in 2003, after data not available. AADT reported for year of conversion where available. Storm Lake AADT not available for 1993; value shown represents first available year (1996). Council Bluffs AADT not available for 2000; value shown represents 1996.
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IOWA 4-LANE TO 3-LANE CONVERSION STUDY
SUMMARY OF STUDY RESULTSBEFORE AND AFTER CONVERSION
"Before" cases based on 5 years of data (except Storm Lake); "after" cases based on 1 to 5 years of data. Year of conversion is not included in the data analysis. Storm Lake "before" data 1991 and 1992 only; conversion in 1993. Clear Lake conversion completed in 2003, after data not available. AADT reported for year of conversion where available. Storm Lake AADT not available for 1993; value shown represents first available year (1996). Council Bluffs AADT not available for 2000; value shown represents 1996.
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ModelModel1st Level
⎟⎠⎞
⎜⎝⎛1000
~ ititit
vPoiy λ
( )iititit
ttittttiitit
idXXX
IttXtXItttXii
++++
−++−+++= >>
493827
)(01615)(043121 00)()(log
βββ
ββββββλ2nd Level
where:
( )( )12,0~ −
bwi Nid τ⎩⎨⎧
≤>
=> t tif 0, t tif 1,
0i
0i)( 0 ittI,
, and
τ2bw is the between-site precision
9 to1 from for ,)1000,0(~ jNjβ )01.0,01.0(~2 gammabwτand
Priors:
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Results/DiscussionResults/Discussion
25.2% (23.2% 25.2% (23.2% -- 27.8%) in 27.8%) in crashes/milecrashes/mile
25%25%
18.8% (17.9% 18.8% (17.9% -- 20.0%) in 20.0%) in crash ratecrash rate
ThreeThree--Lane Cross Section Lane Cross Section with Bike Laneswith Bike Lanes
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Potential DisadvantagesPotential Disadvantages
1.1. Increased delay at Increased delay at unun--signalizedsignalized access access points.points.
2.2. Loss of passing opportunitiesLoss of passing opportunities•• Aggressive DriversAggressive Drivers•• Slow Moving VehiclesSlow Moving Vehicles
3.3. Increased Travel DelayIncreased Travel Delay
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Supplementary Right Turn LanesSupplementary Right Turn Lanes
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Access Control ConsiderationsAccess Control Considerations
Eliminate, consolidate and relocate drivewaysEliminate, consolidate and relocate driveways
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CautionsCautions
ADT greater than 15,000ADTADT greater than 15,000ADTAt grade rail crossingsAt grade rail crossingsSchool bus stopsSchool bus stopsCurbside mailboxesCurbside mailboxes90 degree turns along corridor90 degree turns along corridorHigh volume of slowHigh volume of slow--moving agricultural vehiclesmoving agricultural vehiclesOffset side streets or major access pointsOffset side streets or major access pointsHigh volume turning trucksHigh volume turning trucks
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Which is the Priority?Which is the Priority?
Improving traffic and pedestrian safety while Improving traffic and pedestrian safety while maintaining acceptable traffic flowmaintaining acceptable traffic flow
OrOr
Moving traffic with a minimum amount of delay Moving traffic with a minimum amount of delay and accepting higher safety risksand accepting higher safety risks
????????
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44--Lane to 3Lane to 3--Lane Lane ConversionsConversions
Troy A. Jerman, P.E.Troy A. Jerman, P.E.Senior Transportation EngineerSenior Transportation Engineer
Office of Traffic and SafetyOffice of Traffic and SafetyHighway DivisionHighway Division
Iowa Department of TransportationIowa Department of Transportation800 Lincoln Way800 Lincoln Way