SW 8th Avenue atSW 91st StreetIntersection Modification

Board of County CommissionersNovember 8, 2011

Outline

RecommendationProject Background and LocationTraffic AnalysisComparison of AlternativesPublic MeetingRecommendation

Recommendation

Direct staff to proceed with the design of a signal with left turn lanes at the intersection of SW 8th Avenue at SW 91st Street and proceed with the bid phase when design is complete

Project Background2005 Tower Road Network Study

Examined intersection capacities on Tower Road and surrounding networkAnalysis based on Comprehensive Plan Policy 1.1.4 which adopts LOS D for motor vehicles as the minimum standard for collector and arterial roadsRecommended intersection modifications on Tower Road and at six other locations on the networkSW 8th Avenue at SW 91st Street included in the six network modifications

Design and construction funded with $500,000 of Impact Fees

Project Background

Alachua County Mobility PlanAdopted in April 2011Places emphasis on an interconnected roadway networkExtends SW 8th Avenue to SW 143rd Street and to SW 20th Avenue to serve as an east-west alternative to Newberry Road

8th Avenue Extension

8th Avenue Connector

8th Avenue and 91st Street Intersection ImprovementsI-75 Overpass Widening

Tower Road From Archer Road to 8th Avenue

SW 8th Avenue

SW 91

st Street

Project Location

Scenic Road Protection Area

Volume

Speeds

ClassificationPosted 85th

Percentile

SW 8th Avenue 5,690 40-45 mph 39 mph Major Collector

SW 91st Street 8,000 30 mph 40 mph Major Collector

Traffic Data

Crash Data (2004-2009)No. Type Fatal Injury Contributing Cause

1 Angle 0 0 Failure to Yield Right-of-Way

2 Left Turn 0 0 Disregard Stop Sign

3 Left Turn 0 0 Failure to Yield Right-of-Way

4 Angle 0 0 Failure to Yield Right-of-Way

5 Ditch 0 1 Brake Failure

6 Angle 0 0 Failure to Yield Right-of-Way

7 Angle 0 0 Failure to Yield Right-of-Way

8 Angle 0 0 Failure to Yield Right-of-Way

9 Ditch 0 0 Disregard Stop Sign

10 Angle 0 0 Failure to Yield Right-of-Way

11 Angle 0 0 Failure to Yield Right-of-Way

12 Rear End 0 0 Careless Driving

13 Angle 0 0 Failure to Yield Right-of-Way

14 Rear End 0 0 Careless Driving

15 Angle 0 0 Failure to Yield Right-of-Way

16 Angle 0 0 Disregarded Stop Sign

17 Sideswipe 0 0 Careless Driving

Signal Warrant AnalysisWarrant Applicable Satisfied Comments

1A Minimum Vehicular Volume Yes Yes-100%The required volumes were met at the 70% level during

the peak hour. The 70% level was used because the 85th-percentile speed is 41 mph.

1B Interruption of Continuous Traffic Yes No The required traffic volumes were met for seven out of

the eight required hours.

2 Four Hour Vehicular Volume Yes YesThe required traffic volumes were met for all four hours at the 70% level. The 70% level was used because the

85th-percentile speed is 41 mph

3A Peak Hour Delay No No This warrant is not applicable because there is not a special condition to warrant its use.

3B Peak Hour Volume No YesThe required volumes were met at the 100% level but

this warrant is not applicable because there is not a special condition to warrant its use.

4 Pedestrian Volume No No Only four pedestrians were observed crossing the intersection during the time period studied.

5 School Crossing No No There is not a school located within walking distance of this intersection.

6 Coordinated Signal System Yes NoThe two closest signals are almost a mile away. This

would reduce the effectiveness of the signals to platoon the traffic

7 Crash Experience Yes No There were not enough correctable crashes at this intersection in 2009.

8 Roadway Network Yes Yes Both roads are major routes.

Roundabout JustificationBased on Florida Department of Transportation Roundabout GuideEvaluates intersection in seven categories

Community enhancementTraffic calmingSafety improvementAll-way stop control alternativeLow volume signal alternativeMedium volume signal alternativeSpecial conditions

Roundabout Justification

Evaluation of contraindications (emergency response, right-of-way, etc.)Results of roundabout justification

Roundabout justified as safety improvement, AWSC alternative and low volume signal alternativeDetermined two possible contraindications

Emergency response routeLimited right-of-way

All contraindicating factors can be mitigated

Comparison of AlternativesCompared five alternatives

Existing stop controlTraffic signal with left turn lanes

Signal Layout

Comparison of AlternativesCompared five alternatives

Existing stop controlTraffic signal with left turn lanesSingle lane roundabout with full right turn slip lane

Roundabout 1 Layout

Comparison of AlternativesCompared five alternatives

Existing stop controlTraffic signal with left turn lanesSingle lane roundabout with full right turn slip laneSingle lane roundabout with modified slip lane

Roundabout 2 Layout

Comparison of AlternativesCompared five alternatives

Existing stop controlTraffic signal with left turn lanesSingle lane roundabout with full right turn slip laneSingle lane roundabout with modified slip laneSingle lane roundabout without slip lane

Roundabout 3 Layout

Comparison of AlternativesCompared five alternatives

Existing stop controlTraffic signal with left turn lanesSingle lane roundabout with full right turn slip laneSingle lane roundabout with modified slip laneSingle lane roundabout without slip lane

Compared alternatives in four areasOperational efficiencyEnvironmental impactsSafetyCosts

Operational Impacts

Performed capacity analysis based on Comprehensive Plan Policy 1.1.4

Based on Highway Capacity Manual methodolgiesAnalyzed all options during the AM and PM peak hours in the current year and design year

Reviewed anticipated capacity of SW 24th Avenue at 91st Street roundabout vs. actual

Operational Analysis

Current Year (2010) Design Year (2033)

AM Peak PM Peak AM Peak PM Peak

OverallLOS

OverallAverage

Delay(s)

OverallAverage

Delay(s)

OverallAverage

Delay(s)

OverallAverage

Delay(s)

OverallAverage

Delay(s)

Overall LOS

OverallAverage

Delay(s)

AWSC F 61.1 C 24.2 F 459.4 F 347.2

Signal A 8.2 A 7.4 B 19.1 B 10.3

Roundabout 1 A 6.7 A 7.1 C 25.0 B 14.5

Roundabout 2 A 6.8 A 7.1 C 25.3 B 14.6

Roundabout 3 B 10.0 A 8.6 E 79.9 C 24.4

SW 24th Avenue at SW 91st Street

Year

PM Peak

OverallLOS

Overall Delay Volume

Original Study 2005 A 2.3 1494HNTB Study 2005 B 15.0 1325

Environmental Impacts

Evaluated three areas of environmental impactsPotential tree impactsStormwater runoffGasoline consumption

Tree Impacts - Signal

Tree Impacts – Roundabout 1

Tree Impacts – Roundabout 2

Tree Impacts – Roundabout 3

Tree Impact Summary

IntersectionType

Number of Trees Impacted

AWSC 0

Signal 0Roundabout 1 50-60Roundabout 2 40-50Roundabout 3 40-50

Stormwater - SignalStormwater Impacts – Signal

Stormwater Impacts – Roundabout 1

Stormwater Impacts – Roundabout 2

Stormwater Impacts – Roundabout 3

Stormwater Summary

IntersectionType

Increase in Impervious Area

(Square Feet)AWSC 0Signal 15,500

Roundabout 1 19,800Roundabout 2 13,500Roundabout 3 10,500

Gasoline Consumption

IntersectionType

Gasoline Consumption (gallons)

2010 2033

AM PM AM PM

AWSC 68.0 49.0 319.0 148.0Signal 47.0 39.0 75.0 65.0

Roundabout 1 23.9 24.8 53.4 42.3Roundabout 2 23.9 24.8 53.5 42.3Roundabout 3 30.1 25.3 69.6 45.4

SafetySafety benefits of signals

Potential to reduce head-on, angle and left turn crashesPositive direction to motorists, bicyclists and pedestriansAlerts visually-impaired pedestrians

Safety benefits of roundaboutsLower speeds through intersectionProvides pedestrian refugeReduces conflict pointsSafety benefits decrease as more lanes are added

Comparison of Intersections

IntersectionCrashes Rates (2004-2009)

Total Rate Injury Rate

SW 91st at SW 24th .66 .04

SW 75th at SW 24th 1.23 .27

SW 91st at SW 8th .47 .03

CR 241 at NW 39th .39 .20

Costs

Evaluated total life-cycle costs taking into account:

Right-of-way acquisitionDesignConstructionOperation and maintenance

Right-of-Way - Signal

Existing Right-of-way

Right-of-Way – Roundabout 1

Existing Right-of-way

Proposed Right-of-way

Right- of Way – Roundabout 2

Existing Right-of-way

Proposed Right-of-way

Right-of-Way – Roundabout 3

Existing Right-of-way

Proposed Right-of-way

Right-of-way Needs Summary

IntersectionType

Additional Right-of-way Needed

(Acres)AWSC 0Signal 0

Roundabout 1 .50Roundabout 2 .33Roundabout 3 .25

Operation and Maintenance SummaryIntersection

Type Electric Maintenance Annual Total

Annual Growth

Rate20-year Life

AWSC $ 650 $ 400 $1,050

2%

$26,000Signal $ 650 $ 4,850 $ 5,500 $ 134,000

Roundabout 1 $2,700 $1,500 $ 4,200 $ 102,000Roundabout 2 $2,700 $1,500 $ 4,200 $ 102,000Roundabout 3 $2,700 $1,500 $ 4,200 $102,000

Total Life-Cycle Costs

AWSC Signal Roundabout 1 Roundabout 2 Roundabout 3

Right-of-Way $ - $ - $ 123,000 $ 87,000 $ 78,000

Construction $ - $ 462,000* $ 614,000 $ 435,000 $ 390,000

Design $ - $ 69,000 $ 92,000 $ 65,000 $ 59,000

O&M $ 26,000 $ 134,000 $ 102,000 $ 102,000 $ 102,000

Total Costs $ 26,000 $ 665,000 $ 931,000 $ 689,000 $ 659,000

* Assumes steel mast arm construction

Comparison of AlternativesOperations Safety Environment Costs

AWSC

Signal

Roundabout 1

Roundabout 2

Roundabout 3

Public MeetingHeld on August 18, 2011Noticed through e-mail, mailouts, press releaseOver 60 people in attendanceReceived written comments from 26 individualsPrimary concerns included

Preserving scenic quality of 91st StreetIncreased runoffCostsRight-of-way aquisitionSplit preference between keeping AWSC and roundabout

Recommendation

Direct staff to proceed with the design of a signal with left turn lanes at the intersection of SW 8th Avenue at SW 91st Street and proceed with the bid phase when design is complete

Questions ?