DRAFT FINAL REPORT THE FLORIDA DEPARTMENT OF TRANSPORTATION SYSTEMS PLANNING OFFICE. on Project. Estimation of Capacities on Florida Freeways

Transcription

1 DRAFT FINAL REPORT to THE FLORIDA DEPARTMENT OF TRANSPORTATION SYSTEMS PLANNING OFFICE on Project Estimation of Capacities on Florida Freeways FDOT Contract BDV32 TWO July 22, 2014 by Lily Elefteriadou, Alexandra Kondyli, and Bryan St. George Transportation Research Center The University of Florida

2 DISCLAIMER The opinions, findings, and conclusions expressed in this publication are those of the authors and not necessarily those of the State of Florida Department of Transportation.

3 METRIC CONVERSION CHART U.S. UNITS TO METRIC (SI) UNITS SYMBOL WHEN YOU KNOW LENGTH MULTIPLY BY TO FIND SYMBOL in inches 25.4 millimeters mm ft feet meters m yd yards meters m mi miles 1.61 kilometers km METRIC (SI) UNITS TO U.S. UNITS SYMBOL WHEN YOU KNOW LENGTH MULTIPLY BY TO FIND SYMBOL mm millimeters inches in m meters 3.28 feet ft m meters 1.09 yards yd km kilometers miles mi 3

4 TECHNICAL REPORT DOCUMENTATION PAGE 1. Report No. 2. Government Accession No. 3. Recipient's Catalog No. 4. Title and Subtitle Estimation of Capacities on Florida Freeways 7. Author(s) Lily Elefteriadou, Alexandra Kondyli, Bryan StGeorge 9. Performing Organization Name and Address Transportation Research Center University of Florida 512 Weil Hall, PO Box Gainesville, FL Sponsoring Agency Name and Address Florida Department of Transportation 605 Suwannee Street, MS 30 Tallahassee, FL Supplementary Notes 5. Report Date July 22, Performing Organization Code 8. Performing Organization Report No. 10. Work Unit No. (TRAIS) 11. Contract or Grant No. FDOT Contract BDV32 TWO Type of Report and Period Covered Draft Final 14. Sponsoring Agency Code 16. Abstract Current capacity estimates within Florida s travel time reliability tools rely on the HCM 2010 to estimate capacity under various conditions. Field measurements show that the capacities of Florida freeways are noticeably lower than the values recommended in the HCM 2010, by an order of a few hundred vehicles. In addition, recent research has shown that maximum freeway throughput may differ between undersaturated and oversaturated conditions. The main objective of this research is to collect field data at several urban and rural freeway and multilane locations in Florida in order to measure capacity flows, and to provide recommended capacity values before and after the initiation of oversaturation. The research team obtained data at urban and rural freeways and multilane highway segments across Florida. The urban freeway data were obtained through STEWARD at various types of bottlenecks including merge junctions, weaving segments, as well as geometric bottlenecks (lane drops), while the rural freeway and multilane highway data were obtained from the permanent count stations of FDOT. Incidents and weather data were also obtained to ensure that the final datasets include capacity observations due to excess demand and not due to random events such as incidents or bad weather. Various capacity measures were investigated and it is recommended to define pre-breakdown capacity as the 85th percentile of the 15-min average pre-breakdown flow, and the post-breakdown capacity as the average discharge flow. A clear drop in throughput between pre-breakdown and discharge capacity values was observed. Recommendations on capacity values as a function of the number of lanes and the segment type for both urban and rural locations are offered. This research also proposes revised density thresholds for defining Level of Service at various types of segments consistent with the recommended capacity values. 17. Key Words capacity, bottlenecks, urban freeways, rural freeways, multilane highways, capacity drop 19. Security Classif. (of this report) Unclassified 20. Security Classif. (of this page) Unclassified 18. Distribution Statement No restrictions 21. No. of Pages Price 4

5 EXECUTIVE SUMMARY The Highway Capacity Manual is the publication used most often to estimate capacity. The HCM 2010 indicates that the capacity of a basic freeway segment varies with free-flow speed (FFS) and that under base conditions it ranges from 2,400 pc/h/ln (for FFS 70 or 75 mi/h) to 2,250 pc/h/ln (for FFS 55 mi/h). Similarly, the HCM 2010 indicates that the capacity of a multilane highway segment ranges from 2,200 pc/h/ln (for FFS 60 mi/h) to 1,900 (for FFS 45 mi/h). However, recent research has shown that the maximum freeway throughput may differ between undersaturated and oversaturated conditions, and that the difference may be in the order of a 10% drop in throughput after traffic flow breakdown (i.e., beginning of oversaturated conditions.) Existing models for estimating travel time reliability rely on capacity values in order to estimate travel time under various scenarios, including travel time for undersaturated and oversaturated conditions. Accurate capacity estimates are essential in a) determining whether demand exceeds capacity and congested conditions are to be anticipated, and b) in estimating the expected travel times under various conditions as a function of the demand and the capacity of a segment. Current capacity estimates within Florida s travel time reliability tools rely on the HCM 2010 to estimate capacity under various conditions. Field measurements show that the capacities of Florida freeways are noticeably lower than the values estimated in the HCM 2010, by an order of a few hundred vehicles. Also, field measurements seem to indicate that the capacities at merge junctions are lower than the recommended basic freeway segment capacities. No studies have been identified that estimate or measure the capacity of multilane highways in Florida. The main objective of this research is to collect field data at several urban and rural freeway and multilane locations in Florida in order to capture capacity flows, and to provide recommended capacity values before and after the initiation of oversaturation. The urban freeway data were obtained through STEWARD at various types of bottlenecks including merge junctions, weaving segments, as well as geometric bottlenecks (lane drops), while the rural freeway and multilane highway data were obtained from the permanent count stations of FDOT. In addition to the traffic data, incidents and weather data were also obtained to facilitate the data collection process 5

6 and ensure that the final datasets include capacity observations due to excess demand and not due to random events such as incidents or bad weather. All capacity measures presented are related to the occurrence of breakdown events at the study sites, which are identified through sharp speed drops (e.g., at least 10 mi/h between two time intervals). At the multilane highway sites, breakdown events were not observed, thus, a thorough capacity analysis was not performed. Various capacity measures were investigated such as the breakdown flow, the maximum pre-breakdown flow, the average pre-breakdown flow, and the average discharge flow, as well as a variety of statistics (e.g., 50 th percentile, 85 th percentile), and as expected, these values were considerably lower than the HCM 2010 values. The relationship between capacity and bottleneck type, number of lanes, and free-flow speed was also investigated. Based on the analysis results it is recommended to define pre-breakdown capacity as the 85 th percentile of the 15-min average pre-breakdown flow, and the post-breakdown capacity as the average discharge flow. A clear drop in throughput between pre-breakdown and discharge capacity values is also observed. This research also offers recommended capacity values as a function of the number of lanes and the segment type for both urban and rural locations. This research also proposes revised density thresholds for defining Level of Service at various bottlenecks as a function of the recommended capacity values. 6

7 TABLE OF CONTENTS DISCLAIMER... 2 METRIC CONVERSION CHART... 3 TECHNICAL REPORT DOCUMENTATION PAGE... 4 EXECUTIVE SUMMARY... 5 TABLE OF CONTENTS... 7 LIST OF FIGURES... 9 LIST OF TABLES INTRODUCTION Background Objectives Report Organization DATA COLLECTION Urban Freeways I 95 NB at Butler Boulevard, Jacksonville, FL I 95 NB at University Boulevard, Jacksonville, FL SR 826 EB at NW 47th Avenue, Miami, FL I 4 EB at SR 408, Orlando, FL I 95 NB at NW 103rd Street, Miami, FL I 95 NB at Philips Highway, Jacksonville, FL I 4 EB at I 75, Tampa, FL I 95 NB at the Turnpike, Miami, FL I 95 NB Between Baymeadows Rd. and Butler Blvd, Jacksonville, FL I 4 WB at Lee Road, Orlando, FL Rural Freeways I 75 at CR 514, West of Coleman, Sumter County, FL Turnpike, South of County Road 468, East of Coleman, Sumter County, FL I 75, North of SR 48, West of Bushnell, Sumter County, FL I 95, North of SR 44, West of New Smyrna Beach Volusia County, FL I 75, North of William Road, South of Ocala, Marion County, FL

8 I 95, South of Florida Georgia State Line, Northwest of Yulee, Nassau County, FL I 75, Between I 10 and US 90, West of Lake City, Columbia County, FL I 95, South of Aurantia Road, North of Titusville, Brevard County, FL I 4, East of Enterprise Road, Deltona, Volusia County, FL Multilane Highways US 98, Pensacola Bay Bridge, South of Pensacola, Santa Rosa County, FL Roosevelt Boulevard, Near St. Petersburg Airport, North of St. Petersburg, Pinellas County, FL SR 212, East of Hopson Road, Jacksonville, Duval County, FL DATA ANALYSIS Capacity Definitions Capacity Estimates Comparison with HCM 2010 and FDOT default values CONCLUSIONS AND RECOMMENDATIONS Recommended Capacity Values by Segment Type Recommended Level of Service Thresholds REFERENCES APPENDIX A A.1. Capacity Definitions in the Literature A.2. Capacity Drop Estimates in the Literature

9 LIST OF FIGURES Figure Description of capacity measurement location by (a) merge bottleneck, (b) diverge bottleneck, and (c) weaving bottleneck Figure Schematic of I 95 NB at Butler Boulevard study section in Jacksonville, FL Figure Schematic of I 95 NB at University Boulevard study section in Jacksonville, FL Figure Schematic of SR 826 EB at NW 47th Avenue study section in Miami, FL Figure Schematic of the I 4 at SR 408 study section in Orlando Figure Schematic of I 95 NB at NW 103 rd Street study section in Miami, FL Figure Schematic of the I 95 NB at Philips Highway study section in Miami, FL Figure Schematic of I 4 EB at I 75 study section in Tampa, FL Figure Schematic of I 95 NB at Florida s Turnpike study section in Miami, FL Figure Schematic of I 95 NB Between Baymeadows Road and Butler Boulevard study section in Jacksonville, FL Figure Schematic of the I 4 WB at Lee Road study section in Orlando, FL Figure Schematic of I 75 at County Road 514 study section, Sumter County Figure Schematic of Turnpike South of County Road 468 study section, Sumter County Figure Schematic of I 75 North of SR 48 study section, Sumter County Figure Schematic of I 95 North of SR 44 study section, Volusia County Figure Schematic of I 75 North of William Road study section, Marion County Figure Schematic of I 95 South of Florida Georgia State Line study section, Nassau County Figure Schematic of I 75 Between I 10 and US 90 study section, Columbia County Figure Schematic of I 95 South of Aurantia Road study section, Brevard County Figure Schematic of I 4 East of Enterprise Road study section, Volusia County Figure Schematic of US 98 at Pensacola Bay Bridge study section, Santa Rosa County Figure Schematic of Roosevelt Boulevard Near St. Petersburg Airport study section, Pinellas County Figure Schematic of SR 212 East of Hopson Road study section, Duval County Figure Capacity measures under consideration Figure Capacity comparison results by bottleneck location for urban freeway segments Figure Capacity comparison results by bottleneck location for rural freeway segments Figure Capacity comparison results by number of lanes for urban freeway segments Figure Capacity comparison results by number of lanes for rural freeway segments Figure Capacity comparison results by FFS for urban freeway sites

10 LIST OF TABLES Table HCM (TRB, 2010) Values for Capacity on Freeway and Multilane Highway Segments Table FDOT Peak Hour Directional Volumes and Capacity Values on Various Roadways (FDOT, 2013) Table Capacity Measures for Urban Freeway Sites Table Capacity Measures for Rural Freeway Sites Table Analysis Results for Multilane Highways Table Truck percentages at urban freeway sites Table Selected capacity estimates in pc/h/ln for urban freeways Table Selected capacity estimates in pc/h/ln for rural freeways Table Recommended capacity values for various types of segments (pc/h/ln) Table Recommended capacity values for various types of segments (veh/h/ln) Table LOS criteria for basic, weaving, merge/diverge segments (HCM 2010) Table Density at capacity for urban freeway segments (weave, merge/diverge) Table LOS criteria for weaving, merge/diverge segments (urban freeways) Table Density at capacity for rural freeway segments (basic) Table LOS criteria for basic segments (rural freeways)

11 1. INTRODUCTION 1.1 Background The Highway Capacity Manual is the publication used most often to estimate capacity. The current published version of the HCM (2010) defines the capacity of a facility as... the maximum sustainable hourly flow rate at which persons or vehicles reasonably can be expected to traverse a point or a uniform section of a lane or roadway during a given time period, under prevailing roadway, environmental, traffic, and control conditions. The HCM 2010 indicates that the capacity of freeways and multilane highways varies with free-flow speed (FFS). The HCM capacity values for basic freeway and multilane highway segments (in pc/h/ln) are shown in Table The weaving segments methodology in the HCM 2010 calculates weaving segment capacities (HCM 2010, Equation 12-5). Based on this calculation, the weaving segment capacity is always less than the capacity of a basic freeway segment with the same FFS. The merge/diverge segments methodology of the HCM 2010 does not provide capacity at those segments, but rather a maximum flow entering the merge (ramp flow plus flow at lanes 1 and 2) or the diverge (flow at lanes 1 and 2) area, which is a function of the FFS. The capacity values shown in Table 1. 1 as well as those estimated by equations, represent national averages, and the HCM 2010 indicates that any given location may have higher or lower capacities. Table HCM (TRB, 2010) Values for Capacity on Basic Freeway and Multilane Highway Segments Speed (mi/h) Capacity (pc/h/ln) Basic Freeway Segments 70, 75 2, , , ,250 Multilane Highways 60 2, , , ,900 11

12 Basic freeway segments are rarely bottlenecks (they may form bottlenecks when grades are steep or when other geometric elements are restrictive,) and thus the maximum flows observed at these would not represent capacity unless they are followed by oversaturated conditions. It is not clear whether the values recommended by the HCM represent flows before the breakdown, or maximum flows obtained irrespective of breakdowns. The adopted FDOT peak hour directional volumes for freeways and multilane highways are shown in Table They are provided in units of vehicles rather than PCEs (FDOT, 2013) and thus are noticeably lower than the values provided in the HCM The FDOT values assume 4 percent heavy vehicles on urbanized freeways and 2 percent on highways. For example, if we assume 4 percent heavy vehicles on level terrain and commuter traffic, then the corresponding capacity values for a four-lane urban freeway is approximately 2100 pc/h/ln (PHF is assumed to be 1). Table 1. 2 also provides the corresponding FDOT - recommended capacity values in pc/h/ln based on these truck percentages and for PHF = 1. Table FDOT Peak Hour Directional Volumes and Capacity Values on Various Roadways (FDOT, 2013) Urbanized Areas Freeways Non Urbanized Areas Freeways Lanes veh/h/ln pce/h/ln veh/h/ln pce/h/ln 2 1,970 2,010 1,790 1, ,027 2,070 1,847 1, ,055 2,100 1,875 1, ,072 2,120 1,888 1, ,083 2,130 Urbanized Areas Multilane Hwys* Non Urbanized Areas Multilane Hwys* Lanes veh/h/ln pce/h/ln veh/h/ln pce/h/ln 2 1,795 1,820 1,720 1, ,793 1,820 1,723 1,740 * Divided highway The capacity values of Table 1. 2 are a function of the number of lanes, rather than the FFS. This approach is consistent with previous research (Lu and Elefteriadou, 2013) which found that capacity differs by the number of lanes, and is higher for 3-lane facilities than for 2-lane or 4-12

13 lane facilities. However, in the FDOT capacity values, capacity increases with the number of lanes even beyond 4-lane facilities. FDOT recommends different capacity values for urbanized vs. non-urbanized facilities. Research on freeway capacity (Cassidy and Bertini, 1999; Lorenz and Elefteriadou, 2001; Persaud et al., 2001; Brilon, 2005) has examined the conditions under which breakdown occurs, and concluded that it does not occur deterministically under a given set of volumes. Also, several of these articles have shown that this maximum value does not necessarily coincide with the breakdown event. Lastly, it has also been shown that regardless of whether one uses the maximum pre-breakdown flow, or the breakdown flow to define capacity, both values vary widely on a daily basis even for the same site and for similar traffic conditions. This is inconsistent with traditional traffic analysis methods (HCM 2000, 2010HCM), which assume that traffic transitions to oversaturated conditions (i.e., breakdown event) when demand reaches a specific maximum value, labeled as capacity. Recent research has shown that maximum freeway throughput may be different in undersaturated and oversaturated conditions, and that the difference may be in the range between -7.76% and 17.3% drop in throughput after traffic flow breakdown. It should be noted though, that the literature focuses primarily on freeway merging segments, while there is limited information about the capacity drop percent at weaving, diverging segments, or at lane drops. Current capacity estimates within Florida s travel time reliability tools rely on the HCM 2010 to estimate capacity under various conditions. Field measurements show that the capacities of Florida freeways are noticeably lower than the values estimated in the HCM 2010, by an order of a few hundred vehicles. Also, field measurements seem to indicate that the capacities at merge junctions are lower than basic freeway segment capacities. No studies have been identified that estimate or measure the capacity of multilane highways in Florida. Existing models for estimating travel time reliability rely on capacity estimates in order to estimate travel time under various scenarios, including travel time for undersaturated and oversaturated conditions. Accurate capacity estimates are essential in a) determining whether demand exceeds capacity and congested conditions are to be anticipated, and b) in estimating the expected travel times under various conditions as a function of the demand and the capacity of a segment. Thus, it is important to obtain accurate capacity estimates considering Florida 13

14 conditions such as driver populations, degree of aggressiveness, area types, etc., as well as different types of facilities prevalent in the State Objectives The main objective of this research is to collect field data at several (urban and rural) freeway locations in Florida in order to measure capacity flows, and to provide recommended capacity and the corresponding speed values before and after the initiation of oversaturation. The research team also identified a limited number of suitable locations along multilane highways to conduct a similar analysis. The urban freeway data were obtained through STEWARD at various types of bottlenecks including merge junctions, weaving segments, as well as geometric bottlenecks (lane drops), while the rural freeway and multilane highway data were obtained from the permanent count stations of FDOT Report Organization The next chapter presents the data collection effort undertaken for this project. Chapter 3 presents the data analysis and derivation of capacity values at each site. Chapter 4 presents the formulated recommendations regarding the measurement of capacity as well as recommended values for various types of facilities and for undersaturated and oversaturated conditions. The literature review conducted for this project related to the capacity drop phenomenon and the definition of capacity is provided in Appendix A. 14

15 2. DATA COLLECTION Data from urban freeways, rural freeways and multilane highways were obtained and analyzed. In addition to the traffic data, incidents and weather data were also obtained to facilitate the data collection process and ensure that the final datasets include capacity observations due to excess demand and not due to random events such as incidents or bad weather. All capacity measures presented are related to the occurrence of breakdown events at the study sites. If these are not present we cannot be certain that capacity has been reached. These breakdown events are identified through sharp speed drops (e.g., at least 10 mi/h between two time intervals) recorded either at the upstream or downstream detector relative to the bottleneck (Figure 2. 1). At ramp merge bottlenecks, the freeway capacity is measured downstream of the on-ramp, which corresponds to the downstream detector shown in Figure 2. 1a. At diverge bottlenecks, the freeway capacity is measured upstream of the off-ramp, which corresponds to the upstream detector shown in Figure 2. 1b. At weaving segments, the freeway capacity is measured within the weave area, which corresponds to the subject detector shown in Figure 2. 1c. Further information on the breakdown identification algorithm used in this study, can be found in Kondyli et al. (2013). 15

16 (a) (b) Figure Description of capacity measurement location by (a) merge bottleneck, (b) diverge bottleneck, and (c) weaving bottleneck. (c) 16

17 2.1. Urban Freeways Ten urban freeway sites were examined. The sites were identified based on the following sources: FDOT (2011); Washburn et al. (2010). These sites were selected based on the following criteria: They experience recurrent congestion due to merging, diverging of weaving operations; These bottlenecks are free from downstream congestion; Data are available for approximately one year, excluding weekends and holidays; Weather and incident data are available; The quality of the data is generally considered good. Speed and flow data were obtained from each site from STEWARD at 1-min increments, excluding days with bad weather or incidents. The weather conditions evaluation was conducted using data from the website Days that experienced precipitation over 0.20 inches or foggy conditions were omitted from the analysis. The incident information was obtained through INRIX and through the CAR database provided by the Florida Department of Transportation (FDOT.) If an incident occurred along the study site and within 5 miles downstream, that day was removed from the analysis. The overall quality of the sensor data was evaluated through various sources, such as INRIX, and the STEWARD quality checks. Truck percentages were also available through FDOT at 1-hour increments. The remainder of this section provides site descriptions for each bottleneck location analyzed, accompanied by a schematic (not drawn to scale). The schematics specify the presence of nearby on- and off-ramps, the location of the detectors used to obtain capacity values, as well as other detectors available along the study site I-95 NB at Butler Boulevard, Jacksonville, FL This site is located in Jacksonville, Florida, just downstream of the on-ramp from Butler Blvd (Figure 2. 2). The bottleneck is activated due to weaving operations, and it consists of three lanes per direction with an auxiliary lane. Data are not available for the auxiliary lane, which was excluded from analysis. The weaving length is 4,400 ft. The speed limit at the segment is 65 mi/h 17

18 and the AADT is 112,000 vehicles. Speed data were collected for both detectors shown in red in order to identify the breakdown events. Capacity information was collected from the downstream detector, as indicated earlier and in Figure 2. 1c. I 95 NB N Butler Blvd (EB) Butler Blvd (WB) Bowden Road Detector locations Detectors used Figure Schematic of I 95 NB at Butler Boulevard study section in Jacksonville, FL I-95 NB at University Boulevard, Jacksonville, FL This site is also located in Jacksonville, Florida (Figure 2. 3). The bottleneck occurs due to an on-ramp merge from University Boulevard. The site has three lanes per direction. The posted speed limit is 65 mi/h and the AADT is 118,000 vehicles. Capacity values are measured according to Figure 2. 1a, for merge sites. Both detectors displayed in red were used to obtain speed data and identify the breakdown events. I 95 NB N Bowden Road Detector locations Detectors used University Blvd (WB) University Blvd (EB) Figure Schematic of I 95 NB at University Boulevard study section in Jacksonville, FL 18

19 SR-826 EB at NW 47th Avenue, Miami, FL This site is located in Miami, Florida. The bottleneck is the result of a merge (Figure 2. 4). The mainline has three lanes per direction. It has a speed limit of 55 mi/h and the AADT is 142,500 vehicles. Figure 2. 4 displays a schematic of the study site. Both detectors shown in red were used to evaluate traffic operations and breakdown events at the merge bottleneck. The final capacity values correspond to the detector located downstream of the merge junction with NW 47 th Avenue. SR 826 EB N NW 57 th Ave NW 47 th Ave NW 37 th Ave Detector locations Detectors used Figure Schematic of SR 826 EB at NW 47th Avenue study section in Miami, FL I-4 EB at SR-408, Orlando, FL This site is located in Orlando, Florida along the eastbound direction. The bottleneck occurs due to an on-ramp merge from the intersection with SR-408, as well as a left side on-ramp merge with South Street (Figure 2. 5). The site has three lanes with an auxiliary on the right side; data were not available for this auxiliary lane. The speed limit is dictated by Variable Speed Limit signs, and its base line speed limit is 50 mph. The AADT is 140,000 vehicles. Figure 2. 5 illustrates the study area, along with the detector used. No data were available for the detector located upstream of the Anderson Street ramp. The detector located downstream of the merge from SR-408 WB is used for the capacity analysis. 19

20 I 4 EB N South St S Garland Ave SR 408 EB Anderson St SR 408 WB Detector locations Detectors used N Garland Ave Figure Schematic of the I 4 at SR 408 study section in Orlando I-95 NB at NW 103rd Street, Miami, FL This segment is located in Miami, Florida, and the bottleneck occurs due to the NW 103rd Street on-ramp (Figure 2. 6). The segment has four lanes per direction as well as two HOT lanes; these were not analyzed in this project as they operate independently. The speed limit along the corridor is 55 mi/h and the AADT is 216,000 vehicles. Both detectors shown in red provided speed data to determine breakdown events, while the detector located downstream of the merge is used to gather capacity data. I 95 NB N Turnpike NB NW 81 st St NW 95 th St NW 103 rd St NW 119 th St NW 125 th St NW 135 th St NW 151 st St I 95 NB Detector locations Detectors used Figure Schematic of I 95 NB at NW 103 rd Street study section in Miami, FL I-95 NB at Philips Highway, Jacksonville, FL This segment is located in Jacksonville, Florida. The bottleneck forms due to the on-ramp from Philips Highway (Figure 2. 7). The segment has four lanes along the mainline and the posted speed limit is 65 mph. The AADT is 108,500 vehicles. Speed data were collected at both detectors shown in red, while the detector downstream of the Philips Highway on-ramp was used to gather capacity values. 20

21 I 95 NB N I 295 SB Philips Highway Southside Blvd Detector locations Detectors used Figure Schematic of the I 95 NB at Philips Highway study section in Miami, FL I-4 EB at I-75, Tampa, FL This site is located in Tampa, Florida along the eastbound section of I-4. A bottleneck occurs at the on-ramp merge junction from I-75 NB onto I-4 EB (Figure 2. 8). The speed limit is 70 mph. The bottleneck section has four lanes downstream of the merge and three lanes upstream (lane addition). The AADT is 143,000 vehicles. Both of the detectors shown in red were used to identify breakdown events, while capacity data were collected from the downstream detector. I 4 EB N Detector locations Detectors used I 75 SB I 75 NB Figure Schematic of I 4 EB at I 75 study section in Tampa, FL I-95 NB at the Turnpike, Miami, FL This site is located in Miami, Florida. The section is a major diverge bottleneck located along Florida s Turnpike (Figure 2. 9). The site has three lanes along the mainline, with two lanes exiting towards the Turnpike. The speed limit at the site is 55 mi/h and the AADT is 225,000 21

22 vehicles. Detector data upstream of the diverge were not available, therefore, the detector used for analysis is located immediately downstream of the diverge. I 95 NB N Turnpike NB NW 135 th St Detector locations Detector used NW 151 st St I 95 NB Figure Schematic of I 95 NB at Florida s Turnpike study section in Miami, FL I-95 NB Between Baymeadows Rd. and Butler Blvd, Jacksonville, FL This study site is located in Jacksonville, Florida between Baymeadows Road and Butler Boulevard. The bottleneck is caused by the diverge at Butler Boulevard. The freeway has three lanes per direction and a speed limit of 65 mph. The AADT is 89,500 vehicles. The detectors used for identifying the breakdown events are shown in Figure Since this is a diverge bottleneck, the detector located upstream of the Butler Blvd off-ramp was used to calculate all capacity values. I 95 NB N Baymeadows Road Butler Blvd (EB) Butler Blvd (WB) Detector locations Detectors used Figure Schematic of I 95 NB Between Baymeadows Road and Butler Boulevard study section in Jacksonville, FL 22

23 I-4 WB at Lee Road, Orlando, FL This site is located along a section of I-4 in Orlando, Florida in the westbound direction. The bottleneck occurs due to a reduction in lanes from four to three downstream of an off-ramp onto Lee Road (Figure 2. 11). The speed limit is dictated based on Variable Speed Limit signs, and the baseline speed limit is 50 mph. The AADT is 165,500 vehicles. Capacity values were obtained based on the detector located downstream from the lane drop, while speed information was collected from both detectors labeled in red. I 4 WB N Detector locations Detectors used Lee Road Figure Schematic of the I 4 WB at Lee Road study section in Orlando, FL 2.2. Rural Freeways A total of nine rural freeway sites were analyzed. In contrast to the urban freeway sites, these rural freeways do not experience breakdown regularly, and are not located along bottlenecks. The source of congestion at these sites is the same as in urban sites, which is increased demand. Therefore the focus of the analysis is on obtaining flow data during some of the highest demand days of the year in an effort to approximate capacity values. The study sites were selected based on the results of a previous study (Washburn et al., 2010). In that study, data were collected between November 25, 2009 and November 30, With the help of FDOTs permanent count stations, additional data were collected at the same sites (both directions of travel) between November 2013 and January 2014, in order to record data during the highest demand period at these facilities. All data were available at 10- or 15-min increments. With respect to the data, incident information was not readily available, but after consultation with FDOT the research team was able to remove days with incidents in the vicinity of the sites. Days that experienced poor weather conditions (precipitation over 0.20 inches or 23

24 foggy conditions) were also omitted from the analysis. Weather conditions were evaluated using information from the website Since the permanent count stations were programmed by FDOT to collect data at the study sites for this specific project, the research team did not receive any indication by FDOT personnel regarding bad detector quality, and as such all data are considered to be of good quality. The research team does not have any information on incidents and data quality for the 2009 data. Truck percentages were also available for these sites through FDOT at 1-hour increments. The remainder of this section describes each of the rural freeway study sites and provides the respective schematic (not drawn to scale.) The schematics include nearby on- and off-ramps, as well as the location of the detectors (FDOT s permanent count stations) used for obtaining the speed and flow data I-75 at CR 514, West of Coleman, Sumter County, FL This site is located along I-75 in Sumter County in the vicinity of CR 514 (also called Warm Springs Avenue). The site has two lanes per direction, and its speed limit is 70 mph. The AADT is 40,900. There is a junction at SR-44 approximately 4.8 miles north of the site, and a junction with N CR 470 approximately 3.1 miles to the south. These are not shown in the schematic since they are very unlikely to affect operations (Figure 2. 12). I 75 N I 75 SB I 75 NB Detector used County Road 514 Figure Schematic of I 75 at County Road 514 study section, Sumter County 24

25 Turnpike, South of County Road 468, East of Coleman, Sumter County, FL This site is located along the Turnpike in Sumter County, south of County Road 486 (also called SR-91). It has two lanes per direction, and a speed limit of 70 mph. The AADT is 37,893 vehicles. The Turnpike rest area on- or off-ramps are located nearby (Figure 2. 13). Turnpike N Main Street Turnpike SB Turnpike Rest Area Turnpike NB Detector used County Road 468 Main Street Figure Schematic of Turnpike South of County Road 468 study section, Sumter County I-75, North of SR-48, West of Bushnell, Sumter County, FL This site is located along I-75 in Sumter County, west of Bushnell, FL. It is north of a major junction with SR-48, with on- and off-ramps in close proximity to the study site. The AADT is 38,720 vehicles. The site has two lanes per direction and a 70 mi/h speed limit (Figure 2. 14). I 75 N SR 48 I 75 SB I 75 NB Detector used SR 48 Figure Schematic of I 75 North of SR 48 study section, Sumter County 25

26 I-95, North of SR-44, West of New Smyrna Beach Volusia County, FL The site is north of SR-44 along I-95 in Volusia County, west of the city of New Smyrna Beach. It has two lanes per direction and a speed limit of 70 mph. The AADT is 36,601 vehicles. SR-44 is the nearest junction and is located approximately 2.7 miles north of the site (Figure 2. 15). I 95 N SR 44 SR 44 SR 44 I 95 SB I 95 NB Detector used SR 44 SR 44 Figure Schematic of I 95 North of SR 44 study section, Volusia County I-75, North of William Road, South of Ocala, Marion County, FL This site is located along I-75 in Marion County, south of Ocala, FL. It has three lanes per direction and its speed limit is 70 mi/h (Figure 2. 16). The detector used is approximately 0.35 miles north of William Road. The AADT is 77,544 vehicles. A junction at SW College Road, downstream of the site in the northbound direction, is the access point. I 75 N SB Service Plaza SW College Road I 75 SB I 75 NB Detector used NB Service Plaza William Road SW College Road Figure Schematic of I 75 North of William Road study section, Marion County 26

27 I-95, South of Florida-Georgia State Line, Northwest of Yulee, Nassau County, FL The site is about 2 miles south of the Florida-Georgia State line along I-95 in Nassau County. The nearest town is Yulee, FL to the southeast of the site. The site has three lanes per direction with a speed limit of 70 mph. The AADT is 55,500 vehicles. The detector used is located just downstream of the junction with US-17, in the northbound direction (Figure 2. 17). I 95 N US 17 I 95 SB I 95 NB Detector used US 17 Figure Schematic of I 95 South of Florida Georgia State Line study section, Nassau County I-75, Between I-10 and US-90, West of Lake City, Columbia County, FL The site is located in Columbia County, along I-75, between the I-10 and US-90 interchanges. The nearest city is Lake City to the east. It has three lanes per direction, with a speed limit of 70 mi/h (Figure 2. 18). The AADT is 44,727 vehicles. I 75 N US 90 I 10 I 75 SB I 75 NB Detector used US 90 I 10 Figure Schematic of I 75 Between I 10 and US 90 study section, Columbia County 27

28 I-95, South of Aurantia Road, North of Titusville, Brevard County, FL This site is located along I-95 in Brevard County. It has two lanes per direction with a speed limit of 70 mph. The AADT is 26,000 vehicles. The closest major city is Titusville, FL to the south. The detector is located approximately 0.9 miles south of Aurantia Road, which passes underneath I-95. It is also north of a Service Plaza exclusively for use by the southbound lanes (Figure 2. 19). I 95 N SB Service Plaza I 95 SB I 95 NB Detector used Aurantia Road Figure Schematic of I 95 South of Aurantia Road study section, Brevard County I-4, East of Enterprise Road, Deltona, Volusia County, FL This site is located along I-4 in Volusia County, east of the Enterprise Road overpass in Deltona, FL. It has three lanes per direction, with the Debary Avenue junction closest to the site. The speed limit is 70 mi/h (Figure 2. 20). The AADT is 96,379 vehicles. I 75 N Debary Ave I 4 SB I 4 NB Detector used Debary Ave Enterprise Road Figure Schematic of I 4 East of Enterprise Road study section, Volusia County 28

29 2.3. Multilane Highways Analysis was also performed at three multilane highway sites in Florida. The sites were chosen based on information provided by FDOT, given that these should be at least two miles away from signalized intersections to be categorized as multilane highways according to the HCM 2010 (TRB, 2010). The data were collected between November 21, 2013 and January 6, 2014 for all three sites. All data were available at 15-min increments. Incident information was not readily available along those sites, but after consultation with FDOT we were able to remove data with incidents occurring in the vicinity of the study sites. Days that experienced poor weather conditions (precipitation over 0.20 inches or foggy conditions according to were also omitted from the analysis. Since the permanent count stations were programmed by FDOT to collect data at the study sites for this specific project, the research team did not receive any indication by FDOT personnel regarding bad detector quality, and as such all data are considered to be of good quality. Truck percentage data were not available at these sites. Every site description is accompanied by a schematic of the study site (not drawn to scale.) The schematics include nearby on- and off-ramps, as well as the detector location US-98, Pensacola Bay Bridge, South of Pensacola, Santa Rosa County, FL This site is located along US-98 in Santa Rosa County, and it is at the start of the southern end of the Pensacola Bay Bridge, also known as the Three Mile Bridge. The section has two lanes in each direction and has several driveways in its vicinity, leading to marinas as well as residences. The detector is located approximately 0.7 miles north of the nearest signalized intersection, Northcliff Drive/Fairpoint Drive (Figure 2. 21). The AADT is 51,831 vehicles. The nearest signalized intersection north of the site is approximately 3.3 miles away, at N 17th Avenue. These intersections are not presented in the figure as they are very unlikely to affect operations at the site. The speed limit along the bridge is 45 mph. 29

30 US 98 N Driveway Driveway US 98 SB US 98 NB Driveway Detector used Figure Schematic of US 98 at Pensacola Bay Bridge study section, Santa Rosa County Roosevelt Boulevard, Near St. Petersburg Airport, North of St. Petersburg, Pinellas County, FL This site is located along Roosevelt Boulevard in Pinellas County. It is east of the signalized intersection with 58 th Street North. The detector is placed near an unsignalized intersection, along a section with three through lanes and a speed limit of 45 mph. The AADT is 33,346 vehicles. The eastbound direction also has a left-turn lane at the detector location. The site is very close to the St. Petersburg Airport, and it has many unsignalized intersections along its length (Figure 2. 22). 30

31 Roosevelt Boulevard N Bay Vista Dr Alma Ave Roosevelt Blvd WB Roosvelt Blvd EB 58 th Street N Avalon Ave Detector used Signalized intersection Figure Schematic of Roosevelt Boulevard Near St. Petersburg Airport study section, Pinellas County SR-212, East of Hopson Road, Jacksonville, Duval County, FL The site is located along SR-212, also called Beach Boulevard, in Duval County. It is east of Hopson Road, which provides access to a marina (Figure 2. 23). The site is also just east of the Intercoastal Waterway. It has three lanes per direction and the speed limit is 45 mph. The AADT is 39,301 vehicles. The nearest signalized intersection west of the site is San Pablo Road, approximately 1.4 miles from the detector location, which is shown in the schematic of the site. Hopson Rd SR 212 N SR 212 WB SR 212 EB Detector used Signalized intersection Hopson Rd 20 th Street N Figure Schematic of SR 212 East of Hopson Road study section, Duval County 31

32 3. DATA ANALYSIS This section first provides a description of the six different definitions of capacity for oversaturated and undersaturated conditions. Next, it presents the resulting numerical values for each capacity definition for all study segments Capacity Definitions Based on the literature review findings, six definitions were considered and their respective values were obtained from the data: A. Breakdown flow: the 1-minute flow per lane immediately before the breakdown event (i.e., before the abrupt speed drop). B. Maximum 1-min pre-breakdown flow within 15 minutes: the 1-min highest flow that occurs during the 15 minutes before the breakdown, i.e., during undersaturated conditions. C. Maximum 5-min pre-breakdown flow within 15 minutes: the 5-min highest flow (rolling average) that occurs during the 15 minutes before the breakdown, i.e., during undersaturated conditions. D. Average 5-min pre-breakdown flow: the average 5-minute flow per lane immediately before the breakdown during undersaturated conditions. E. Average 15-min pre-breakdown flow: the average of the 15-minute flow per lane immediately before the breakdown during undersaturated conditions. F. Average discharge flow: the average flow per lane during oversaturated conditions (i.e., the time interval after breakdown and prior to recovery). Figure 3. 1 identifies the data points that correspond to each of the above capacity definitions in a time series plot. 32

33 Speed (mi/h) C E B D A 14:52:0 14:57:0 15:2:0 15:7:0 15:12:0 15:17:0 15:22:0 15:27:0 15:32:0 15:37:0 15:42:0 15:47:0 15:52:0 15:57:0 16:2:0 16:7:0 16:12:0 16:17:0 16:22:0 16:27:0 16:32:0 16:37:0 16:42:0 16:47:0 16:52:0 16:57:0 17:2:0 17:7:0 17:12:0 17:17:0 17:22:0 Time F Flow (veh/h) Figure Capacity measures under consideration. For urban freeways we report the following pre-breakdown capacity measures: breakdown flow, maximum 1-min or 5-min pre-breakdown flows, the average 5- and 15-minute pre-breakdown flows. For the rural freeways and multilane highways 5- minute data were not always available, therefore these were analyzed in 10-minute or 15-minute intervals depending on data availability. All capacity measures presented are related to the occurrence of breakdown events at the study sites. When breakdown does not occur, we cannot be certain that the demand has been high enough so that capacity can be reached. Breakdown events are identified through sharp speed drops (e.g., at least 10 mi/h between two time intervals) recorded either at the upstream or downstream detector relative to the bottleneck, as discussed in the previous chapter Capacity Estimates This section provides a summary of the data analysis performed to extract the capacity measures specified earlier: breakdown flow, maximum (1-min or 5-min) pre-breakdown flow, average (5- min or 15-min) pre-breakdown flow and average discharge. Table 3. 1 presents the average, minimum, maximum, standard deviation, and 50 th and 85 th percentiles of the breakdown, prebreakdown, and discharge capacity measures for the ten urban freeway sites. The results 33

34 presented in this table are divided into groups based on the type of bottleneck and the number of lanes. Table Capacity Measures for Urban Freeway Sites Site I-95 NB, At Butler (Jacksonville) I-95 NB, At University (Jacksonville) SR-826 EB, At NW 47 th Ave. (Miami) I-4 EB, At SR-408 (Orlando) I-95 NB, At NW 103 rd St (Miami) Capacity Values (veh/h/ln) Pre-Breakdown 5-Min Avg Number of Observations (breakdowns) Statistic Breakdown 5-Min Max 1-Min Max Weave, 3 Lanes on Mainline with an Auxiliary Lane 15-Min Avg Discharge Average Min Max St. Dev th Percentile th Percentile Merge, 3 Lanes on Mainline Average Min Max St. Dev th Percentile th Percentile Average Min Max St. Dev th Percentile th Percentile Composite (Right followed by left side) Merge, 3 Lanes on Mainline Average Min Max St. Dev th Percentile th Percentile Merge, 4 Lanes on Mainline Average Min Max St. Dev th Percentile th Percentile

35 Site I-95, At Philips Hwy (Jacksonville) I-4 EB, At I- 75 (Tampa) I-95 NB, At Turnpike (Miami) I-95 NB, at Baymeadows and Butler (Jacksonville) I-4 WB, At Lee Road (Tampa) Number of Observations (breakdowns) Capacity Values (veh/h/ln) Pre-Breakdown Statistic Breakdown 5-Min Max 1-Min Max 5-Min Avg 15-Min Avg Discharge Average Min Max St. Dev th Percentile th Percentile Merge, 3- to 4-Lanes (lane addition) Average Min Max St. Dev th Percentile th Percentile Major Diverge, 5 Lanes, 3 Lanes on Mainline Average Min Max St. Dev th Percentile th Percentile Diverge, 3 Lanes on Mainline Average Min Max St. Dev th Percentile th Percentile Diverge, 4 to 3 Lanes (lane drop) Average Min Max St. Dev th Percentile th Percentile Table 3. 2 presents the capacity measures for the rural freeway sites. The raw data were provided at a 10- or 15-minute aggregation level; therefore the capacity measures reported 35