Practices in One-Lane Traffic Control on a Two-Lane Rural Highway (2018)

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84 The survey and interview results presented in Chapter 3 showed that 1L2W operations are being more commonly applied at roundabouts. Additionally, applications of TPRSs and DADs are increasing. This chapter describes innovative examples of traffic control used in roundabouts, deployment of TPRSs, and use of DADs in 1L2W operations. Roundabouts Colorado, Pennsylvania, Oregon, and Washington State DOTs are the only responding agencies who have developed typical TTC applications for 1L2W operations in roundabouts. PennDOT has developed typical applications for short-term stationary 1L2W traffic control when work space is on one quadrant of a roundabout (see Figure 4-1), on one entrance of a roundabout (see Figure 4-2), and on one exit of a roundabout (see Figure 4-3). Figure 4-4 illustrates Oregon’s typical application for 1L2W traffic control in roundabouts. When a portion of the roundabout needs to be closed, traffic may be held in place if closure is 20 minutes or shorter (ODOT 2016a). ODOT states that for closures of an approach leg, at least two flaggers shall be used. Additional flaggers for the remaining legs maybe required if approach traffic volumes are high. A typical application for 1L2W traffic control in roundabouts used by Colorado and Wash- ington State are shown in Figure 4-5 and Figure 4-6, respectively. In general, available information on 1L2W traffic control in roundabouts is limited. The typical applications only utilize flagger control, and design thresholds (e.g., maximum allowable traffic volumes on approaches), number of flaggers to provide efficient and safe operations, and managing vehicle flows lack quantifiable guidelines. TPRSs TPRSs are used in 1L2W TTC zone operations mainly to reduce speed and increase driver awareness of upcoming conditions. During the SHRP program, TPRSs were tested in a 1L2W zone in Ohio, and it was shown that use of the TPRS reduced average vehicle speeds and increased driver recognition of TTC zone signing (Stout et al. 1993). In 2010, a field evaluation in Kansas explored the effectiveness of TPRSs in reducing vehi- cles’ speed and affecting drivers’ behavior in flagger-controlled 1L2W zones (Wang et al. 2013). Four different scenarios were evaluated: (1) normal traffic conditions with no main- tenance activity, (2) maintenance activity with standard flagger control, (3) maintenance activity with human flagger control and two sets of TPRSs, and (4) maintenance activity C H A P T E R 4 Case Examples

Case Examples 85 Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. See Table 3-10 for distance and spacing (D, E, and H). 3. Each flagger shall be clearly visible to traffic for a minimum distance of E. 4. Shall be used when making a complete circle in a roundabout or traffic circle is prohibited. 5. If a shadow vehicle is not present, 50 feet are measured from end of taper to beginning of work space. Figure 4-1. Pennsylvania typical application when work is on one quadrant of a roundabout (PennDOT 2014).

86 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. See Table 3-10 for distance and spacing (D, E, and H). 3. Each flagger shall be clearly visible to traffic for a minimum distance of E. 4. Shall be used when making a complete circle in a roundabout or traffic circle is prohibited. 5. If a shadow vehicle is not present, 50 feet are measured from end of taper to beginning of work space. Figure 4-2. Pennsylvania typical application when work is on one entrance of a roundabout (PennDOT 2014).

Case Examples 87 Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. See Table 3-10 for distance and spacing (D, E, and H). 3. Each flagger shall be clearly visible to traffic for a minimum distance of E. 4. Shall be used when making a complete circle in a roundabout or traffic circle is prohibited. 5. If a shadow vehicle is not present, 50 feet are measured from end of taper to beginning of work space. Figure 4-3. Pennsylvania typical application when work is on one exit of a roundabout (PennDOT 2014).

88 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Note: 1. A, B, and C distances are listed in Table 3-16. Figure 4-4. Oregon typical application for 1L2W operations at roundabouts (ODOT 2016a). with human flagger control and three sets of TPRSs. Field data were collected at three sites with speed limits of 55 and 65 mph. The AADT volumes were between 770 and 2,000 vpd. It was found that when standard human flagger control operations were supplemented by TPRSs, average vehicle speeds were reduced between 6 mph and approximately 14 mph. This reduction in average speed was statistically significant. Between 30% and 80% of the drivers activated their brake when they approached the TPRSs, and 5% of the drivers swerved around the TPRSs. Guidance for the Use of Temporary Rumble Strips in Work Zones gives detailed introductions on the features, types, and effectiveness of temporary rumble strips (ATSSA 2013a). Guidelines

Case Examples 89 Note : 1. Distances between signs (A, B, and C) for rural highways are 500 feet. Figure 4-5. Colorado standard plan for 1L2W operations at roundabouts (CDOT 2016). are also provided for when and how to implement TPRSs in TTC zones. The advantages of TPRSs as listed by ATSSA are the following: • Ease of installation and removal compared to permanent rumble strips, • Potential for reuse of rumble strips, • Increased driver awareness of upcoming conditions and compliance with other traffic control devices, and • Increased braking and reduced speeds. The disadvantages of TPRSs were the following: • Potential for erratic or avoidance maneuvers by drivers, • Potential rough ride or hazard for motorcycles and/or bicyclists,

Note: 1. Sign spacing (X) is listed in Table 3-17. Figure 4-6. Washington typical application for 1L2W operations at roundabouts (WSDOT 2015a).

Case Examples 91 • Potential for movement of rumble strips due to inadequate installation, and • Noise complaints by nearby residents. Five types of TPRSs introduced in the ATSSA guidance were (1) preformed thermoplastic, (2) pavement marking tape, (3) adhesive, (4) manually adhesive, and (5) portable reusable rumble strips. Features of the five types of temporary rumble strips are the following: • Preformed thermoplastic rumble strips do not require the roadway to be pre-heated and have the benefits of flexibility and conforming to the roadway, which make them durable and resistant to movement on the roadway. • Pavement marking tape can be layered and built up to the desired thickness, which is between 8 and 10 mm. The tape is generally highly adhesive, but still depends on pavement conditions and vehicle movements. • Adhesive rumble strips are manufactured with a removable adhesive backing and can be cut to desired lengths. Several studies showed that a thickness of 0.25 inches was enough to produce an alert sound level comparable to that of permanent rumble strips, with the effectiveness of reducing car speeds by less than 2 mph, reducing truck speeds by 3 to 5 mph, and reducing the percentage of vehicles exceeding the posted speed limit in the advanced warning area. • Manually adhesive rumble strips were tested in Wisconsin at a rural intersection, but no significant changes in vehicle speeds were found after using the rumble strips. Manu- ally adhesive rumble strips can also produce a sound level comparable to that of perma- nent rumble strips, and the multiple colors and reflective features potentially make this type of rumble strip provide good visual cues for both daytime and nighttime TTC zone operations. • Portable reusable rumble strips do not need adhesives, which is convenient for situations where daily installation and removal are needed. In terms of producing sound and vibration, this type of rumble strip performed better than adhesive rumble strips and manually adhesive rumble strips. In terms of reducing vehicle speeds, this type of rumble strips helped reduce vehicle speeds by a range of 4 to 10 mph, with different thicknesses (0.8125 inches or 0.83 inches) and different spacing and grouping. In 1L2W operations, Caltrans requires two sets of TPRSs be placed on each direction (Caltrans 2015). Figure 4-7 illustrates Caltrans’ typical application for 1L2W traffic control using TPRSs. Buffer space distances recommended by Caltrans are listed in Table 4-1. TPRSs are positioned near the FLAGGER AHEAD [C29 (CA)] and ONE LANE ROAD AHEAD (W20-4) signs. If one of the following conditions is met, TPRSs are not required: • Work duration of 4 hours or less, • Speed limit below 45 mph, • Emergency work, and • Snow or icy weather conditions. In Kansas, KDOT employment of TPRSs in 1L2W operations is optional (KDOT 2015b). When the roadway width (including paved shoulder) is 30 feet or less, TPRSs may be used instead of lead-in channelizing devices. TPRSs may be used in Ohio when 1L2W operation is short-term stationary, and work crews are present and working within the traveled way (Ohio DOT 2017). Ohio DOT does not allow the use of TPRSs during wet or icy pavement conditions, on chip seal surfaces, or on road- way surfaces with rutting that negatively affects the surface contact area between the TPRS and the roadway. In cases where erratic driver behavior (e.g., avoidance measures and hard brak- ing) becomes apparent, TPRSs and related signs shall be completely removed. TPRSs shall be used with the human flagger control method and shall occur after deployment of all required

Notes: 1. For rural roadways, spacing of advance warning signs (A, B, and C) is 500 feet. Buffer space distances (D) are listed in Table 4-1. 2. C9A(CA) and C45(CA) are California signs. Figure 4-7. Traffic control in 1L2W operations with rumble strips adopted from California Standard Plan T13 (Caltrans 2015).

Case Examples 93 signs. To maintain the required spacing and orientation, TPRSs shall be periodically inspected. Figure 4-8 shows typical application of TPRSs recommended by Ohio DOT. Depending on ADT and length of work area, one or two sets of TPRS arrays may be used in 1L2W operations in Texas (TxDOT 2012c). TxDOT states that TPRSs may be used with human flagger, AFAD, or TTCS control methods. The RUMBLE STRIPS AHEAD sign should be located after the ROAD WORK AHEAD sign. When the vehicle queue is expected to extend beyond the TPRSs, the RUMBLE STRIPS AHEAD sign and the first TPRS array may be located upstream of the ROAD WORK AHEAD sign. The TxDOT standard for TPRS application is shown in Figure 4-9. The number of rumble strip arrays, distance between strips in an array, and sign spacing required by TxDOT are listed in Table 4-2, Table 4-3, and Table 4-4, respectively. The distance between the TPRSs and the flagger station varies in the typical applications pro- vided by Caltrans, KDOT, Ohio DOT, and TxDOT. In addition, conditions under which state DOTs require TPRS deployment are different. DADs A DAD is a TTC device that is designed to regulate driveway traffic in 1L2W TTC zones. Various types of DADs have been tested or are being currently tested by state DOTs. TxDOT conducted a motorist survey and a field test to evaluate experimental devices and strategies to control traffic entering from low-volume access points (Finley et al. 2014). Two sets of devices were tested in field: (1) a modified traffic control device called a “modified hybrid device” that had a circular red and two yellow arrow indications (see Figure 4-10) and (2) a “blank-out sign device” that had a circular red indication and two illuminated blank-out signs (see Figure 4-11). According to a laptop-based motorist survey carried out in 2012 that queried motorists’ understanding of the modified hybrid and blank-out sign devices, both of the device types could be adequately understood by motorists when displaying messages to proceed in a certain direction. However, the modified hybrid device was not as well understood as the blank- out sign device under the stop condition. Results from a field study carried out by the same group of researchers suggested the same conclusion. To further understand the benefits and costs of TTC devices for access points, TTI research- ers carried out a delay analysis in the same study (Finley et al. 2014). Five scenarios were created in Vissim micro-simulation software to reflect different strategies used in TTC zone and access point traffic control, as shown in Table 4-5. Posted Speed Limit (mph) Min D (feet) Downgrade Min D (feet) −3% −6% −9% 20 115 116 120 126 25 155 158 165 173 30 200 205 215 227 35 250 257 271 287 40 305 315 333 354 45 360 378 400 427 50 425 446 474 507 55 495 520 553 593 60 570 598 638 586 65 645 682 728 785 70 730 771 825 891 75 820 866 927 1,003 Source: (Caltrans 2015) Table 4-1. Buffer space recommended by Caltrans.

Figure 4-8. Typical application for TPRSs in Ohio (Ohio DOT 2017).

Notes: 1. Each rumble strip array should consist of three rumble strips spaced center to center at the spacing shown in Table 4-3, placed transverse across the lane at locations shown. 2. See Table 4-4 for sign spacing distance (X). Figure 4-9. TxDOT standard for TPRSs in 1L2W operations (TxDOT 2012c).

96 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Flagger to Flagger (Length of Work Area) (mile) ADT Number of Rumble Strip Arrays 1/8 4,500 1 4,500 2 1/4 3,500 1 3,500 2 1/2 2,600 1 2,600 2 1 1,600 1 1,600 2 > 1 NA 2 Source: (TxDOT 2012c) Table 4-2. Number of rumble strip arrays required by TxDOT. Speed (mph) Distance Between Strips (feet) 40 10 40 & 55 15 55 20 Source: (TxDOT 2012c) Table 4-3. Approximate distance between strips in an array recommended by TxDOT. Posted Speed (mph) Sign Spacing (feet) Suggested Longitudinal Buffer Space (feet) 30 120 90 35 160 120 40 240 155 45 320 195 50 400 240 55 500 295 60 600 350 65 700 410 70 800 475 75 900 540 Source: (TxDOT 2012c) Table 4-4. TxDOT sign spacing and suggested buffer space. (a) (b) Figure 4-10. Modified hybrid device tested in Texas: (a) stop phase and (b) left-turn phase. (Finley et al. 2014).

Case Examples 97 (a) (b) Figure 4-11. Blank-out sign device tested in Texas: (a) stop phase and (b) left-turn phase (Finley et al. 2014). Main Road Access Point Flagger Flagger PTCS Flagger PTCS PTCS PTCS Modified Hybrid Device PTCS Blank-Out Sign Device Source: (Finley et al. 2014) PTCS = portable traffic control signal Table 4-5. TTC methods. The results of the analysis showed that the use of a portable traffic control signal (PTCS) (without vehicle detection) increased delay for the main road and the access point traffic (Finley et al. 2014). The modified hybrid device and blank-out sign device used in the study could work in conjunction with PTCS; therefore, they did not impact primary road delay. The hybrid devices needed between 1 to 4 years for financial recovery (e.g., cost payback). Although safety was not quantified and considered in the study, it is essential when making decisions about access point traffic control devices. TxDOT submitted a FHWA request to experiment with DADs and received approval on June 27, 2013 (Finley et al. 2014). The field study site was at an intersection (Road 916 and County Road 418) on a two-lane rural road with a posted speed limit of 60 mph and an AADT of 1,450 vpd. The length of the lane closure was approximately 4,500 feet. Only one of the two ends of the lane closure was visible to drivers on the side road (County Road 418). Each traffic control device was deployed on the side road over 1 day. Researchers examined motorist understand- ing of the two prototype devices using a controlled study. Researchers also conducted a non- controlled field study focusing on the drivers that had no prior knowledge of the device. For the controlled study, 16 participants were recruited. During the controlled test, all of the participants reacted correctly to the blank-out test while only 57% of participants reacted correctly to the modified hybrid device (Finley et al. 2014). During the non-controlled test, 23% and 13% of the drivers did not comply with the blank-out sign device and the modified hybrid device, respectively. Overall, the analysis showed that the flashing yellow arrow indications used with the modified hybrid device were not well under- stood by drivers. The circle/slashes used over the directional arrows on the blank-out sign device helped drivers to understand the sign.

98 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway The New Jersey Department of Transportation deployed DADs while repairing roadways damaged by Hurricane Sandy (see Figure 4-12). From late 2013 to early 2015, 31 DADs were implemented and no incident or crash was reported (Finley 2017). Devices used in New Jersey were horizontal, including one circular red and two flashing red arrow indications. The supple- mentary signs were a NO TURN ON RED sign and a YIELD IN DIRECTION OF FLASHING RED ARROW AFTER STOP sign. MDOT is testing a DAD design that consists of a red circular and two flashing red arrow indications. Circular red indications inform motorists that they should not enter the TTC zone. Flashing red arrow indications inform motorists of the direction of traffic traveling within the TTC zone. The supplementary signs are a NO TURN ON RED sign and a PROCEED ON FLASHING RED ARROW AFTER STOP sign. Figure 4-13 illustrates an example of DADs implemented in Michigan. MDOT submitted a request to experiment to FHWA to test DADs. With FHWA approval, MDOT officially started to test DADs on July 23, 2015. Several locations—including M-68 in Tower, Michigan—were selected for evaluation. Although DADs are designed to regulate traffic at driveways, MDOT tested their efficiency on specific side roads with low traffic volumes (ADT less than 400). Preliminary results indicated that the DADs oper- ated well and provided sufficient access for given traffic volumes. DADs are also being tested in North Carolina. The supplementary signs used by the North Carolina Department of Transportation are a NO TURN ON RED sign and a TURN ONLY IN DIRECTION OF ARROW sign (see Figure 4-14). Other state DOTs, including Florida and Massachusetts, are also considering the utilization of DADs and are in early stages of testing. The initial implementation of DADs clearly shows the need for standards and guidelines describing uniform design and implementation. Variation in the DADs testing to date is signifi- cant. Texas and North Carolina DOTs tested DADs with yellow arrows while Michigan and New Jersey DOTs tested devices with red arrows. The supplementary signs and location of DADs are not consistent. It is not clear how existing signs and traffic control devices should be managed, especially when they conflict with DADs. Driver understanding and comprehension of DADs also requires further investigation. Figure 4-12. DADs implemented in New Jersey (Finley 2017).

Case Examples 99 Summary Roundabouts are becoming more common across the United States requiring a uniform approach to 1L2W operations at and through roundabouts. The use of TPRSs and DADs in 1L2W operations are also increasing. A limited number of state DOTs have developed standards, guidelines, and typical applications to address these implementations. Only four state DOTs are known to have developed typical applications for lane closures in roundabouts. All four states have considered only human flagger control applications. Handling Figure 4-13. An example of a DAD implemented in Michigan (Brookes 2017). (a) Stop Phase (b) Proceed Phase Figure 4-14. DADs implemented in North Carolina (Courtesy: North Carolina DOT Work Zone Traffic Control Section).

100 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway different roundabout configurations, proper design threshold, and managing circulating vehi- cles requires further investigation. Caltrans, KDOT, Ohio DOT, and TxDOT have developed typical applications for TPRSs in 1L2W operations. These typical applications vary in terms of the location of TPRSs and condi- tions for utilizing them. DAD experimentation across the United States shows that standards and guidelines for designing and implementing DADs are lacking. Texas, North Carolina, Michigan, and New Jersey DADs vary in terms of supplementary signs and directional indications. Sufficient field data to evaluate the effectiveness of the devices in regulating traffic are required. Further investigation is required regarding locating the devices, managing existing signs and traffic control devices, and understanding drivers’ behavior when DADs are utilized.