Traffi c Analysis and Roundabout Concept Development for San Marco Avenue (SR A1A)/ Prepared for: San Carlos Avenue/May Street St. Augustine, Florida Revised, March 2014 Florida Department of Transportation District Two Prepared by: HDR Engineering, Inc. TRAFFIC ANALYSIS AND ROUNDABOUT CONCEPT DEVELOPMENT FOR SAN MARCO AVENUE (SR A1A) AT SAN CARLOS AVENUE/MAY STREET ST. AUGUSTINE, FLORIDA PREPARED FOR: Florida Department of Transportation District Two PREPARED BY: HDR Engineering, Inc. 265 SW Malone Street, Suite 111 Lake City, FL 32025-0018 Revised, March 2014 TABLE OF CONTENTS Page Introduction ..................................................................................................................... 1 Traffic Data Collection .................................................................................................... 1 Field Review .................................................................................................................... 3 Operational Analysis Results ...................................................................................... 10 Traffic Analysis Summary and Conclusions .............................................................. 16 Conceptual Design ....................................................................................................... 18 Appendices .................................................................................................................... 19 Appendix A – Traffic Analysis Appendix B – Roundabout Design Criteria Appendix C – Roundabout Conceptual Design Plans Appendix D – WB-50 Vehicle Paths Appendix E – LRE Construction Cost Estimate Revised, March 2014 Traffic Analysis & Roundabout Concept Development San Marco Ave (SR A1A) at San Carlos Ave/May St LIST OF TABLES Page Table 1 - Weekday versus Saturday Total Intersection Volume Comparison ......................... 1 Table 2 – Intersection Operational Analysis Summary ......................................................... 11 Table 3 – Roundabout vs. Signalized Intersection Delay Thresholds by LOS ...................... 12 Table 4 – Queue Analysis Summary ..................................................................................... 12 Table 5 – Travel Time Comparison ....................................................................................... 15 Table 6 – Roundabout Construction Cost and Right of Way Impacts ................................... 18 LIST OF FIGURES Page Figure 1 - Site Location Map ................................................................................................... 2 Figure 2 – Existing Intersection Geometry .............................................................................. 5 Figure 3 – Intersection Signal Phasing ................................................................................... 6 Figure 4 – Trolley and Boat Traffic .......................................................................................... 7 Figure 5 – Westbound Queue between US 1 and San Marco Avenue ................................... 7 Figure 6 – Westbound Queue on May Street .......................................................................... 8 Figure 7 – Predominant Movements and Maximum Observed Queuing ................................ 9 Revised, March 2014 Traffic Analysis & Roundabout Concept Development San Marco Ave (SR A1A) at San Carlos Ave/May St INTRODUCTION The following memorandum documents the analysis conducted in support of a study to determine the need and viability of a single-lane modern roundabout at the intersections of San Marco Avenue (SR A1A) with San Carlos Avenue and May Street (SR A1A) located in St. Augustine, St. Johns County, Florida. Figure 1 shows the location of the study intersections. TRAFFIC DATA COLLECTION Eight-hour intersection turning movement counts were conducted at the San Marco Avenue intersections at San Carlos Avenue and May Street on Saturday, August 31st, 2013 and Tuesday, September 10th, 2013 to document the traffic volumes on both a peak holiday weekend as well as a typical weekday. As shown in Table 1, the total weekday PM peak hour volumes are very similar to the total Saturday PM peak hour volumes, while the total Saturday AM peak hour and midday peak hour (MD) traffic is 15 to 20 percent higher than the total weekday AM and MD traffic. Table 1 - Weekday versus Saturday Total Intersection Volume Comparison San Marco Ave / San Carlos Peak San Marco Ave / May St Ave Hour Period Weekday Saturday % Diff Weekday Saturday % Diff AM 1474 1771 20% 1254 1475 18% MD 1555 1792 15% 1335 1545 16% PM 1795 1784 -1% 1529 1507 -1% Subsequent to the initial traffic counts, an additional eight-hour turning movement count was conducted at the adjacent signalized intersection at US 1/San Carlos Avenue on Wednesday, January 8, 2014. This count data was collected to allow the US 1 intersection to be incorporated into the roundabout analysis to determine if it would be negatively impacted by queuing extending east from the US 1 intersection, which is located approximately 370 feet to the west of the San Marco Avenue/San Carlos Avenue intersection. To allow the US 1 intersection traffic data to be correlated to the previously collected traffic data, an additional eight-hour intersection turning movement count was completed at the San Marco Avenue/San Carlos Avenue intersection concurrently with the US 1 intersection traffic count. The differences in the San Marco Avenue/San Carlos Avenue intersection count data were used to adjust the US 1 traffic count data to match it to the traffic levels at the San Marco Avenue/San Carlos Avenue intersection from August and September 2013. Revised, March 2014 Traffic Analysis & Roundabout Concept Development San Marco Ave (SR A1A) at San Carlos Ave/May St 1 PROJECT SITE Figure 1 | Location Map Sources: Esri, DeLorme, NAVTEQ, USGS, Intermap, iPC, NRCAN, Esri Japan, As shown in Table 1, the weekday PM peak hour had the highest traffic volumes, while the Saturday PM peak hour volumes were similar to those during the midday peak hour (the highest Saturday volumes). Because the PM peak hour conditions for the weekday and Saturday days represented the worst case traffic conditions, the traffic analysis and simulation was limited to just the PM peak hour. Figure A-1 and Figure A-2 in Appendix A show the PM peak hour volumes at the three study intersections for the existing weekday and holiday weekend day conditions, respectively. Figure A-3 and Figure A-4 in Appendix A present the same PM peak hour traffic volumes for the existing weekday and holiday weekend day conditions, respectively, but with the two San Marco Avenue intersections converted to a single lane, five-leg roundabout. Field Review A field review was conducted on Saturday, August 31st, 2013 to evaluate the operations of the study intersection over the Labor Day weekend. The field review documented the operating conditions of the study intersections; verified geometric characteristics, signage and traffic signal phasing; and, documented the predominant movements at the intersection and queuing observed. The following subsections present a summary of the field observations. Roadway Network San Marco Avenue (SR A1A) has two closely-spaced intersections at San Carlos Avenue and May Street (SR A1A) which are controlled by two signals. The signals are operated under one controller and have coordinated timing and phasing. The US 1 / San Carlos Avenue intersection, located approximately 370 feet west of the San Marco Avenue/San Carlos Avenue intersection also operates in coordination with these two signals. Downtown St. Augustine is located approximately one mile to the south and the intersections provide a vital link for motorists traveling north-south on San Marco Avenue and east-west between US 1 to the west and the beaches to the east. Two of the study roadways are designated as SR A1A, as the alignment comes from the south on San Marco Avenue and turns east on May Street and heads towards the beaches. Roadway Characteristics San Marco Avenue, San Carlos Avenue and May Street are all two-lane, undivided roadways with low posted speeds ranging from 20 to 30 mph. The drainage systems include both closed (curb and gutter) and open (sheet flow into swales) systems. US 1 is a four-lane divided highway with a posted speed of 40 mph in the vicinity of the San Carlos Avenue intersection. Revised, March 2014 Traffic Analysis & Roundabout Concept Development San Marco Ave (SR A1A) at San Carlos Ave/May St 3 Intersection Geometry The junction of San Marco Avenue with San Carlos Avenue and May Street is formed by the San Carlos Avenue and May Street east-west roadways intersecting the north-south San Marco Avenue roadway. May Street and San Marco Avenue form a T-intersection that is located approximately 160 feet north of the four-leg San Carlos Avenue and San Marco Avenue intersection. At the May Street intersection, there are currently exclusive turn lanes provided for the northbound right turn (channelized), southbound left turn, and westbound left turn. At the San Carlos Avenue intersection, there is an exclusive turn lane provided for the northbound left turn. The US 1 / San Carlos Avenue intersection provides an exclusive southbound left turn lane, but only a single westbound lane on San Carlos Avenue. Figure 2 illustrates the existing intersection geometry. Intersection/Signal Operations The two signalized intersections forming the San Marco Avenue / San Carlos Avenue/ May Street junction operate on one controller