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

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36 Information on current organizational practices regarding 1L2W operations at rural highway TTC zones was obtained using a survey questionnaire. This chapter summarizes the findings from the survey questionnaire and follow-up telephone interviews and explains organizations’ practices, perspectives, and experiences with 1L2W operations. A survey questionnaire was developed and beta tested among Topic 48-11 panel members. The revised questionnaire, presented in Appendix B, was distributed to transportation organiza- tions through the AASHTO Subcommittee on Construction. An invitation list was further aug- mented by inviting members of the FHWA Work Zone contacts at state DOTs. Responses from 45 state DOTs and Canadian transportation organizations representing Manitoba, Northwest Territories, and Ontario were received (see Figure 3-1). Survey respondents are listed in Appen- dix D. Following the review of survey questionnaire results from responding organizations, seven organizations were identified for telephone interviews to obtain additional information, case examples, and other documents as appropriate. The survey questionnaire was organized into three sections: • Section 1 applied to contractor operations that have been let to bid for highway construction or maintenance work done by contractors. Respondents were asked to complete this section if their organization was involved only with let-to-bid operations or the organization had dif- ferent policies for let-to-bid and in-house operations. • Section 2 applied to in-house staff performing 1L2W traffic control. Respondents were asked to complete this section if their organization was involved only with in-house operations or the organization had different policies for let-to-bid and in-house operations. • Section 3 applied to both in-house and let-to-bid operations. Respondents were asked to complete this section if their organization was involved with both in-house and let- to-bid operations or the organization had similar policies for let-to-bid and in-house operations. Only the Delaware Department of Transportation (DelDOT), the Massachusetts DOT (MassDOT), and WisDOT reported that they perform 1L2W operations only with contractors. Mississippi DOT is the only state that conducts 1L2W traffic control only with in-house staff. Of the 41 states that perform both in-house and let-to-bid operations, 10 state DOTs (includ- ing Alaska, Arizona, Indiana, Kansas, Missouri, Nevada, Oklahoma, Oregon, South Carolina, and Wyoming) reported different policies or standards for the two types of operations. Responses from three Canadian organizations—Manitoba Infrastructure, Northwest Terri- tories Department of Transportation, and Ontario Ministry of Transportation—were received. Manitoba Infrastructure performs both in-house and let-to-bid operations, while the other two organizations only perform let-to-bid operations for 1L2W traffic control. C H A P T E R 3 Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 37 Survey questionnaire responses were analyzed, and documents obtained from responding organizations including typical applications, standards, guidelines, and manuals were reviewed. The rest of this chapter presents the findings with respect to traffic analysis, design thresholds, methods, side road and driveway treatment, end-of-queue management, mandatory use of PCMSs, and project coordination in 1L2W TTC zones. Traffic Analysis Capacity and lane closure analysis for 1L2W operations are often done by consulting the HCM (TRB 2010). Michigan, Missouri, Oregon, Vermont, and Washington State DOTs provide thresholds and/or methods for calculating capacities and vehicle delays in 1L2W TTC zones. For example, the Michigan Department of Transportation (MDOT) requires traffic analysis during the scoping phase of the projects. Mobility impacts of the projects on the transportation system should be reviewed considering the following critical thresholds: • Volume to capacity: greater than 0.80; • Additional delay: more than 10 minutes; and • Level of Service (LOS): lower than or equal to LOS D (or LOS C if the current operation is LOS A). If the mobility impacts of a project are greater than the critical thresholds, the project is deemed “significant,” and a transportation management plan must be developed. MDOT currently Figure 3-1. State DOTs and Canadian transportation organizations that participated in the survey questionnaire.

38 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway allows design engineers to evaluate mobility impacts using Synchro micro-simulation, graphs, or a software tool called Construction, Congestion, Cost (CO3). Figure 3-2 shows a graph devel- oped by MDOT and the University of Michigan to determine capacity of 1L2W TTC zones based on the posted speed limit in the TTC zone and the length of closure. The graph does not apply to roadways that include signalized intersections. CO3 is a software tool that can be used by engineers to estimate the magnitude and impacts of traffic congestion during a construction project (Carr 1998). CO3 measures the impact of congestion in two ways: • Different characteristics of congestion are evaluated considering variables such as delay, diverted vehicles, and backup; and • User costs including direct (due to increased travel distance/time) and indirect costs (due to delays and trip cancellations) are evaluated and compared with construction cost. User manuals and Microsoft Excel spreadsheets for using CO3 are provided on the MDOT website. MDOT states that the tool should be used to estimate travel-time delay in TTC zones for different TTC zone alternatives (MDOT 2010b). MoDOT uses a graph to estimate average peak-hour delay when a TTCS is utilized in 1L2W TTC zones (see Figure 3-3). Average delay greater than 75 seconds in the peak hour is the thresh- old beyond which TTCSs are not recommended. The factors considered are distance between stop bars and construction year ADT. ODOT utilizes a web-based tool to examine work zone traffic analysis (WZTA). The web- based WZTA tool provides lane closure restrictions and delay estimates resulting from construc- tion, maintenance, utility work, or incident response (ODOT 2010). WZTA can be used for various types of TTC zone projects including 1L2W operations. A screenshot of the web-based Figure 3-2. Capacity in 1L2W TTC zones (MDOT 2006).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 39 WZTA is shown in Figure 3-4. To determine lane closure restrictions, capacity of the road segment and expected demand are determined. Lane closure restrictions are recommended if anticipated demand is greater than the maximum amount of traffic a highway can handle while maintaining a free flow situation. During the development of the web-based WZTA tool, ODOT did not follow the HCM methodology for highway capacity analysis. The methodology and thresholds were determined based on experience, technical observations, and engineering judgment. Suggested free flow thresholds for 1L2W TTC zones are listed in Table 3-1. Note that free flow thresholds are in passenger car equivalents (PCEs) per hour and include the combined traffic volume from both directions. Delay functions used in the web-based WZTA tool were estimated using micro-simulation and regression analyses. Over 100,000 combinations of roadway types, traffic volumes, truck percentages, terrain, and staging strategies were simulated in CORSIM, a commonly used micro-simulation software program. Documentation regarding the estimated delay functions was not available. Traffic volume thresholds for lane closures on two-lane highways recommended by the Vermont Agency of Transportation (VTrans) are listed in Table 3-2. The values were deter- mined based on 25 mph speed, volume/capacity less than or equal to one, 50-50 directional split, and two-phase operation. If flagging operations cease during peak hours of traffic [work during hours below design hourly volume (DHV)], ADTs may be exceeded (VTrans 2011). Capacity for rural highways and two-lane roadways suggested by the Washington State Department of Transportation (WSDOT) are 800 and 400 vehicles per hour per lane, respec- tively. However, WSDOT advises that these values are average capacity values and the HCM should be used to determine actual capacities considering factors including traffic speed, truck percentage, type of work, etc. (WSDOT 2015b). Figure 3-3. Average peak-hour delay for TTCSs on 1L2W operations (MoDOT 2017).

40 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Figure 3-4. A screenshot of the web-based TTC zone traffic analysis tool (Toews and Jackson 2008). PCEs per hour Closure Length (mile) 550 1.0 to 2.0 750 0.5 to 1.0 900 < 0.5 > 900 No Closure Typically Allowed Source: (ODOT 2010) Table 3-1. Free flow thresholds for 1L2W TTC zones. Length of Closure (feet) Max DHV Maximum ADT 2,500 500 4,000 1,500 1,000 7,500 1,000 1,500 11,500 Source: (VTrans 2011) Table 3-2. VTrans thresholds for lane closures in 1L2W operations.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 41 Design Thresholds State DOTs use different design criteria for selecting traffic control methods in 1L2W opera- tions. These design criteria commonly include length of closure, vehicle delay, traffic volumes, and speed. State DOTs often require justification and traffic management plans when design criteria are not met. Design thresholds documented in state DOT guidelines/standards for 1L2W operations are listed in Table 3-3. Maximum length of closure varies between 100 feet and 4 miles depending on the traf- fic control method employed. Several state DOTs do not provide length of closure limits in 1L2W operations. Single flagger and self-managed controls have lower length of closure thresholds, while pilot car and human flagger control (one flagger at each end) have higher thresholds. (continued on next page) State Maximum Length of Closure Maximum Vehicle Delay (min) Traffic Volume (vpd) Other Alaska 20 California 2 miles 30 (preferably less than 20) Delaware 1,000 feet Florida 2 miles AFAD: 800 feet TTCS: 0.25 miles Georgia 2 miles Iowa Single Flagger: 100 feet Human Flagger: 2,000 feet Self Managed: 350 feet TTCS: 960 feet TTCS (< 3 days): 1,340 feet Pilot Car (ADT < 2,500): 2.5 mile Pilot Car (ADT 2,500–5,000): 2 miles Pilot Car (ADT > 5,000): 1.5 miles Pilot Car:15 Self Managed & Single Flagger: 2,000 Kansas 15 Maine 5 Michigan 2 miles Single Flagger: 400 Single Flagger: Speed < 45 mph Minnesota Self Managed without STOP: 500 feet Self Managed without STOP: 200 feet Single Flagger: 500 feet (Work area) 15 Single Flagger & Self Managed with STOP sign: 1,500 Self Managed without STOP sign: 400 Missouri Human Flagger and TTCS: 3 miles AFAD: 0.5 miles 20 Montana 15 Nebraska TTCS: 1,500 feet 15 Nevada Pilot Car: 30 Table 3-3. Design thresholds used by state DOTs for 1L2W operations.

42 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway South Dakota Self Managed: 600 feet 15 Texas Self Managed: 400 feet Self Managed: 2,000 Vermont 1,000–2,500 feet 10 Virginia 2 miles AFADs: 800 feet Flag Transfer: 1 mile 10 (> 500 vpd) 15 (< 500 vpd) Self Managed: 500 AFADs: 12,000 Washington AFADs: 800 feet TTCS: 1,500 feet 20 Wisconsin 800 feet Self Managed: 350 feet 15 Self Managed: 1,000 (or 100 vph) Wyoming 20 North Carolina 1 mile 5 Ohio Human Flagger: 2,000 feet (stationary), 5,000 feet for non- federal aid paving operations, and 9,000 feet for federal aid paving operations Oregon Human Flagger: 1 mile TTCS: 1,000 feet Pilot Car: 3–5 miles Self Managed: 200 feet 20 Self Managed & Single Flagger: 400 TTCS: 3,500 PCE < 900 Single Flagger: Sight distance > 750 feet at each end and posted speed < 40 mph Pennsylvania Pilot Car: 4 miles Self Managed & Single Flagger: 350 feet Self Managed & Single Flagger: 1,500 Pilot Car: 5,000 South Carolina Human Flagger: 2 miles Single Flagger: 200 feet AFADs: 2 miles Human Flagger: 5 (< 1 mile), 7.5 (1–2 miles), 20 (side roads) State Maximum Length of Closure Maximum Vehicle Delay (min) Traffic Volume (vpd) Other New Mexico Single Flagger: 400 Table 3-3. (Continued). When a single flagger is used, length of closure thresholds range between 100 and 500 feet. Length of closure thresholds are slightly greater (200 feet and 600 feet) when self-managed con- trol is used. AFADs are often allowed when the closure length of 1L2W TTC zones is less than 0.5 miles. Maximum lengths of closure with TTCSs are often less than those with pilot car and human flagger control; this is mainly due to communication and excessive delay issues. Com- munication and coordination of TTCSs becomes problematic in long 1L2W sections, especially if there are multiple traffic signals at side roads. If the length of closure is long and a pre-timed signal control is used, unacceptable vehicle delays can occur. When self-managed or single flagger methods are utilized, traffic volumes are commonly less than 2,000 vpd. For example, ODOT requires PCEs of fewer than 900 passenger cars per hour in 1L2W operations. Other methods are open to higher traffic volumes. ODOT allows TTCSs when traffic volumes are 3,500 vpd. VDOT allows AFADs when traffic volumes are as high as 12,000 vpd.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 43 Maximum allowable vehicle delays vary between 5 and 30 minutes. Speed limit is also considered in selecting proper 1L2W methods. For example, MDOT and ODOT require that when a single flagger is utilized, the speed limit should be less than 45 and 40 mph, respectively. Methods Traffic control methods discussed in the MUTCD (FHWA 2009) include human flagger con- trol, flag transfer, self-managed control, AFADs, TTCSs, and pilot car operations. In addition, several state DOTs utilize advance flagger methods. This section describes each of the 1L2W traffic control methods used by state DOTs on two-lane rural highways. Human Flagger Human flagger control is the most common traffic control method for 1L2W operations among state DOTs. Figure 3-5 shows the frequency of human flagger control deployment for various types (only in-house, only let-to-bid, or both in-house and let-to-bid) of 1L2W opera- tions. Thirty-seven state DOTs use human flagger control frequently or exclusively in 1L2W operations. ADOT&PF and MassDOT are the two state DOTs that rarely use human flagger control for let-to-bid operations. MassDOT utilizes police details to flag traffic at most 1L2W TTC zone setups. Important factors considered in selecting human flagger control for 1L2W operations include topography, length of closure (distance), alignment, time of work (daytime, nighttime, working hours, or non-working hours), and work duration (short term or long term). Weather condi- tions tend to be less important factor. Additional details on factors considered are presented in Appendix C (Table C-1). Figure 3-5. Frequency of human flagger method deployment in 1L2W operations by state DOTs.

44 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Flagger stations need to be placed at locations that provide safe operations. For example, several state DOTs, such as the Arizona Department of Transportation (ADOT), state that flagger stations in rolling or mountainous terrain should be placed at the top and bottom of the grade, if possible. When there is a flagger station at the top of a grade, a brake check area should be established (ADOT 2010). Iowa DOT requires that flaggers in rural areas should generally be located a minimum of 350 feet in advance of the work area (Iowa DOT 2015). The Iowa DOT standard for flagger position is shown in Figure 3-6. The MUTCD (FHWA 2009) states that two flaggers (one flagger at each end) should control 1L2W operations. When the length of closure is short enough that a flagger can see from one end to the other, a single flagger can be utilized for traffic control. If a single flagger station cannot maintain good traffic control and visibility, flaggers at each end of the TTC zone should control traffic. State DOTs consider different conditions in using a single flagger: • Iowa DOT indicates that a single flagger can be used if traffic volumes are less than 2,000 vpd, sight distance is adequate, and the length of closure is less than 100 feet. When traffic conflicts and delays become excessive, two flaggers should be utilized (Iowa DOT 2015). • MDOT states that a single flagger can be utilized only if all of the following conditions are satisfied (MDOT 2010a): 1. The work area is short. 2. The work area has good visibility from both approaches and is on a straight section of road. 3. Traffic volumes are less than 400 vpd. 4. Traffic speeds are less than 45 mph. When a single flagger is used (MDOT 2010a): 1. It is recommended to use an oversized STOP/SLOW paddle. 2. The flagger should have a predetermined escape path and should be positioned on the shoulder directly opposite from the work area. 3. Visibility and motorist awareness should be increased by using channelizing devices. 4. While stopping approaching vehicles, the flagger may need to move a short distance toward the end of the TTC zone. 5. Standard flagger control shall be used when traffic fails to understand the single flagger. • In roadways with good visibility and ADT of less than 1,500, MnDOT allows single flaggers to control traffic in 1L2W operations. In this case, the flagger is positioned in the closed lane and Figure 3-6. Iowa standard for flagger position (Iowa DOT 2015).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 45 stops the traffic approaching in the closed lane. Traffic in the opposite direction flows free. The flagger allows traffic in the closed lane to proceed when the open lane is clear. When ADT is less than 400 vpd, fewer advance signs are required. If the decision sight distance beyond the TTC zone is not available, flaggers at each end should be utilized. During high peak periods or in cases where there is a major intersection near the activity area, two flaggers may be required (MnDOT 2014). Figure 3-7 illustrates single flagger typical applications provided by MnDOT. TTC distance charts provided by MnDOT are listed in Table 3-4. • Montana Department of Transportation (MDT) requires that when more than 10 vehicles are stopped at a flag station 50% of the time, a second flagger should be provided (MDT 2014b). • ODOT states that a single flagger can be utilized unless any of the following conditions exist (ODOT 2016a): 1. Nighttime operations. 2. The length of closure is more than 200 feet. 3. The sight distance from each approach through the lane closure is less than 750 feet. 4. ADT is more than 400. Notes: 1. Sight distance shall be at least the Decision Sight Distance. 2. If sight distance beyond the work space is less than the Decision Sight Distance, two flaggers shall be used. 3. The Flagger and Flagger Ahead sign may be omitted if the operation is during daylight hours, 12 hours or less, and traffic is able to self-regulate. 4. When the posted speed limit is 40 mph or less, the ONE LANE ROAD AHEAD sign may be removed. 5. The two-way taper should be 50 feet. 6. If the work space must be left unattended at night use self-regulated control with STOP signs. (a) (b) Figure 3-7. MnDOT single flagger typical application: (a) ADT less than 400 and (b) ADT less than 1,500 (MnDOT 2018).

46 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway • VDOT allows usage of a single flagger for 1L2W traffic control when length of closure is short, sufficient sight distance is available, and traffic volumes are less than 500 vpd. Shadow vehicles are used in the human flagger control method. Standards and guidelines provided by several state DOTs for using shadow vehicles are as follows: • MoDOT allows protective (also called shadow) vehicles for human flagger control operations. When a shadow vehicle is used, the vehicle should be placed at least 150 feet in advance of the activity area. When adequate sight distance exists and work vehicles use activated rotat- ing lights or strobe lights, the shadow vehicle may be eliminated. Protective vehicles are not required for construction operations. For long-term operations, flags and the advance warning rail system (three barricade rails used to enhance the target value of certain signs) shall be used on advance signs (MoDOT 2017). • When human flagger control is used, VDOT requires a shadow vehicle located in advance (80 feet to 120 feet) of the first work crew encountered by traveling motorists (VDOT 2015b). MassDOT, on rare occasions, allows flaggers to control traffic in 1L2W TTC zones. The major- ity of 1L2W operations in Massachusetts are controlled by law enforcement officers. MassDOT policy states that the use of flaggers shall primarily be restricted to roadways with low traffic volume and low speed (less than 45 mph within the limits of the TTC zone). Flaggers can be used on higher speed roadways if ADT is less than 4,000 vpd. Certified flaggers shall be utilized if the requested police detail cannot be filled by a police organization (MassDOT 2011). Flagger Training and Certificate The majority of state DOTs require flaggers to participate in training sessions and obtain cer- tificates. The American Traffic Safety Services Association (ATSSA) and National Safety Council are two national agencies that provide training and certifications for the road safety industry. Table 3-5 summarizes the survey questionnaire results regarding state DOTs’ requirements for flagger training and certificate programs. Posted Speed Limit Prior to Work Starting (mph) Advance Warning Sign Spacing (A) (feet) Decision Sight Distance (D) (feet) Buffer Space (B) (feet Taper Length (L) feet) (G) (feet) 0–30 100 550 200 200 25 35–40 325 700 305 325 25 45–50 600 900 425 600 50 55 750 1,200 500 700 50 60–65 1,000 1,400 650 800 50 70–75 1,200 1,600 820 900 50 Source: (MnDOT 2018) Table 3-4. MnDOT TTC distances. Operation Training/Certificate Yes No Number of Responses In-house Flagger Training 78% 22% 9 Flagger Certificate 78% 22% 9 Let-to-bid Flagger Training 100% 0% 12 Flagger Certificate 92% 8% 12 In-house & Let-to-bid Flagger Training 87% 13% 31 Flagger Certificate 74% 26% 31 Table 3-5. State DOTs’ requirements for flagger training and certificate programs.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 47 Many state DOTs—including Kansas (KDOT 2015a), Maine (Maine DOT 2014), Massachusetts (MassDOT 2011), Montana (MDT 2014b), Nebraska (NDOR 2007), and Virginia (VDOT 2015a)— require flaggers to carry their certification card with them at all times while performing flagging activities. Flagger Apparel (Beyond MUTCD Requirements) The MUTCD provides guidelines for flagger apparel during daytime and nighttime oper- ations. The MUTCD states that flaggers shall wear safety apparel that meets Performance Class 2 or 3 requirements of the ANSI/ISEA 107-2004 publication entitled “American National Standard for High-Visibility Apparel and Headwear” (FHWA 2009). The most recent Ameri- can National Standard for High-Visibility Apparel and Accessories (ANSI/SEA 107-2015) has updated the requirements for high-visibility apparel and accessories; thus, work zone manual flagging practices will require adoption of the ANSI 107-2015 standard. To improve visibility, state DOTs such as VDOT only allow safety apparel that meets Performance Class 3 require- ments. Survey questionnaire results for responding state DOTs that have developed guidelines for flagger apparel are presented in Table 3-6. Flagger-to-Flagger Communication The MUTCD states that when flaggers are utilized, all flaggers should be able to communicate to coordinate the control of the traffic (FHWA 2009). Communication can be oral, electronic, or manual signals. Some DOTs require other methods, in addition to flaggers, in situations where flagger communication is a concern. For example, the Florida Department of Transportation (FDOT) states that if visual contact between flaggers is not available, flaggers should be equipped with two-way radios or pilot vehicles or TTCSs should be used (FDOT 2017c). When visual con- tact between flaggers is not available, MDT states that constant radio contact between flaggers and pilot cars should be maintained using two-way very high frequency or ultra-high frequency FM radios (MDT 2014b). New Mexico Department of Transportation (NMDOT) indicates that pilot car and/or two-way radios should be utilized when flaggers cannot properly communicate through hand signals (NMDOT 2012). Personnel Management The Occupational Safety and Health Administration (OSHA) regulates workers’ health and safety by setting and enforcing standards applicable to work zone operations in all states (OSHA n.d.). Some DOTs also include personnel management guidelines related to topics such as breaks, meal breaks, fatigue avoidance, and heat illness prevention. Arizona, Maine, Missouri, New Jersey, Pennsylvania, South Dakota, Tennessee, Vermont, and Virginia DOTs report guide- lines regarding personnel management procedures. Since continuous flagging operations are required throughout the duration of work activities, adequate certified flaggers shall be avail- able onsite to ensure continuous operations during flaggers’ break periods (Maine DOT 2014). Survey questionnaire results for responding DOTs with personnel management guidelines in each operating method are listed in Table 3-7. Operation Yes No Number of Responses In-house 90% 10% 10 Let-to-bid 75% 25% 12 Let-to-bid & In-house 68% 32% 31 Table 3-6. Flagger apparel guidelines developed by state DOTs.

48 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Night Flagging The MUTCD states that flagger stations shall be illuminated when nighttime flagging is per- formed (FHWA 2009). An average horizontal luminance of 5, 10, and 20 foot-candles can be adequate for general activities, activities around equipment, and activities with a high level of precision and extreme care, respectively. State DOTs including Michigan (MDOT 2010a), Maine (Maine DOT 2014), and Montana (MDT 2014b) require a minimum luminance level of 10 foot-candles at flagger stations. WSDOT indicates that flaggers should be visible and discern- able as a flagger from a distance of 1,000 feet (WSDOT 2016a). For nighttime flagging, flagger apparel should meet the Performance Class 3 requirements (FHWA 2009). Illumination guidelines for nighttime highway work are presented in NCHRP Report 498 (Ellis et al. 2003). Survey questionnaire results for DOTs with night flagging guide- lines are presented in Table 3-8. Human flagger control is widely used by state DOTs due to its many advantages. Thirty-seven state DOTs use human flagger control frequently or exclusively in 1L2W operations. Several state DOTs have provided guidelines to improve the safety and efficiency of human flagger control methods. State DOTs often allow a single flagger to control traffic when sufficient sight distance is available and traffic volumes are below 2,000 vpd. Supporting the health and well-being of flaggers is important, as noted by several state DOTs who have implemented personnel management guide- lines. A sufficient number of certified flaggers is required to ensure continuous flagging operations. Human Flagger with Advance Flagger An advance flagger is not commonly used by state DOTs to control traffic in rural 1L2W opera- tions. Figure 3-8 shows the frequency with which the flagger with the advance flagger control method was used by state DOTs that responded to the survey questionnaire. Arizona DOT often utilizes advance flaggers for let-to-bid operations, and Oklahoma DOT used them for in-house operations. Twenty-three state DOTs indicated that they never utilize advance flaggers in 1L2W operations. Sight distance is the most commonly cited factor for selecting the advance flagger method for 1L2W operations (see Appendix C, Table C-2). Specifically, in cases where the back of the queue extends beyond the initial advance signs and sight distance is limited, an advance flagger is deployed. Several guidelines for using advance flaggers are as follows: • The California Department of Transportation (Caltrans) uses advance flaggers on mountain- ous roads that often do not have enough shoulder and don’t offer appropriate escape room for Operation Yes No Number of Responses In-house 20% 80% 10 Let-to-bid 17% 83% 12 Let-to-bid & In-house 23% 77% 31 Table 3-7. Work zone personnel management guidelines. Operation Yes No Number of Responses In-house 67% 33% 9 Let-to-bid 91% 9% 11 Let-to-bid & In-house 67% 33% 30 Table 3-8. State DOT night flagging guidelines.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 49 flaggers. These roads often have horizontal or vertical curvilinear geometries. In these situations, advance flaggers need to stay in the tangent to maintain some level of visibility, which increases safety concerns. Also, advance flaggers must avoid shadows, which could make it hard for drivers to see them. Caltrans experience shows that when drivers pass the advance flagger and do not see the back of the queue, they often speed up, rendering the advance flagger deployment ineffective. Additionally, a lack of guidelines, policy, or standards for the advance flagger method makes it difficult to determine the advance flagger station location and proper procedures. • When vehicles approaching a TTC zone do not have sufficient sight distance of a flagger or storage space for stopped vehicles, Maine DOT states that additional flaggers shall be utilized at the rear of the stopped vehicles or at a point where approaching motorists have sufficient stopping sight distance to the rear of the stopped traffic (Maine DOT 2014). • In cases with limited sight distance or long traffic queues, MnDOT states that an advance flagger may be utilized. When sight distance is limited, the advance flagger should stop each vehicle and inform the driver of the situation ahead. If there is a long vehicle queue, the advance flagger should move down the vehicle queue and inform each driver of the approxi- mate length of the delay and the reason for the delay (MnDOT 2014). • ODOT requires advance flaggers when traffic queues extend beyond the initial advance warn- ing sign and sight distance from the approaching vehicle and back of the queue is insufficient (ODOT 2016b). Advance flaggers are rarely used by state DOTs. Nevertheless, state DOTs that do deploy this method often utilize it when sight distance is limited or traffic queues may extend beyond the initial advance warning signs. Flag Transfer The flag transfer method is the least common method for 1L2W traffic control. This method provides a means of communication between flaggers by asking the driver of the last vehicle proceeding into the 1L2W TTC zone to transfer a flag to the flagger at the other end of the TTC zone. Figure 3-9 shows the frequency of flag transfer deployment for various types of 1L2W operations among state DOTs. Figure 3-8. Flagger with advance flagger method deployment in 1L2W operations by state DOTs.

50 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway The MUTCD requires that this method be employed only when the one-lane section is relatively short, usually less than one mile in length (FHWA 2009). A major drawback of the flag transfer method is that drivers may not hand in the flag at the other end, and conse- quently, flaggers lose effective communicate and efficiencies. State DOTs such as California (Caltrans 2014a) and Texas (TxDOT 2011) DOTs have removed flag transfer method from their guidelines due to its drawbacks. MnDOT policy states that the flag transfer method may be used when two flaggers are used and two-way radios are unavailable (MnDOT 2014). Flag transfer is not utilized by the three Canadian organizations that responded to the survey questionnaire. Self-Managed Control In self-managed control, traffic is regulated by STOP signs or YIELD signs without the pres- ence of a flagger. In cases with very low traffic volumes, traffic is provided with only advance signing without the use of STOP or YIELD signs. The frequency of self-managed control deploy- ment for various types of 1L2W operations is shown in Figure 3-10. A majority of state DOTs do not utilize self-managed control for 1L2W operations. WisDOT and ADOT are two DOTs that use self-managed control in let-to-bid operations. The most pertinent factors considered in choosing the self-managed control method are topography, length of closure, sight distance, and duration of work (see Appendix C, Table C-4). Self-managed control can be effectively used in short-term 1L2W operations where length of closure is short and sufficient sight distance is available. Specific examples of state DOT metrics for selection of self-managed control include the following: • When the activity area is less than 200 feet and ADT is less than 1,500 vpd, MnDOT allows STOP sign control in 1L2W TTC zones, as shown in Figure 3-11 (MnDOT 2018). If ADT is less than 400 vpd, the length of the activity area is less than 500 feet, and duration of work is 12 hours or less, during daylight traffic can be regulated by advance signs only. If traffic cannot regulate itself, a single flagger control [see Figure 3-7 (a)] should be used. Figure 3-9. Flag transfer method deployment in 1L2W operations by state DOTs.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 51 • In Missouri, MoDOT utilizes self-managed control when all of the following conditions exist (MoDOT 2017): 1. The highway does not have edgelines (see Figure 3-12). 2. Sufficient sight distance is available, and drivers from both directions can see through and beyond the work site. 3. Workers are not present. • In Oregon, ODOT uses self-managed control if all of the following conditions are met (ODOT 2016a): 1. The length of work space is less than 200 feet. 2. The posted speed limit is 40 mph or less (unless not posted and speed governed by basic rule). 3. ADT is less than 400 vpd. 4. Sight distance at each end is more than 750 feet. • The Pennsylvania Department of Transportation (PennDOT) provides typical applications for self-managed stop control, which can be applied when ADT is not more than approxi- mately 1,500 vpd and sight distance between the two STOP signs is unobstructed (PennDOT 2014). • For long-term operations in Texas, TxDOT states that self-managed traffic control should be limited to roadways with ADT less than 2,000 vpd and work spaces less than 400 feet long. Otherwise, traffic should be controlled by portable traffic signals (TxDOT 2012b). • In Virginia, VDOT implements self-managed control in 1L2W TTC zones when traffic vol- umes are less than 500 vpd (VDOT 2017). Additionally, PennDOT and MoDOT have developed standards for short-term and long- term traffic control using self-managed control as follows: • For work operations that last more than 3 days, MoDOT requires a stop bar to be installed (see Figure 3-12). Temporary pavement markings should be installed as soon as practicable, and existing conflicting markings should be removed (MoDOT 2017). Advance warning sign spacing and distances recommended by MoDOT are listed in Table 3-9. Figure 3-10. Self-managed method deployment in 1L2W operations by state DOTs.

52 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Notes: 1. Approach signs are the same in both directions. 2. STOP signs shall be 48 x 48 inch. 3. If adequate sight distance is not available, two flaggers or TTCS should be used. 4. When the posted speed limit is 40 mph or less, the ONE LANE ROAD AHEAD sign may be removed. 5. The two-way taper should be 50 feet. 6. A and G distances are listed in Table 3-4. 7. Type A low-intensity flashing warning light shall be visible on a clear night from a distance of 3,000 feet. Figure 3-11. Minnesota typical application for self-managed control for operations lasting less than 3 days (MnDOT 2018).

Note: 1. S and B distances are listed in Table 3-9. Figure 3-12. Missouri typical application for self-managed yield control (MoDOT 2017). Permanent Posted Speed (mph) S* (feet) B* (feet) 0–35 200 280 40–45 350 400 50–55 500 560 60–70 1,000 840 Source: (MoDOT 2017) *See Figure 3-12. Table 3-9. MoDOT advanced warning sign distance and spacing reference.

54 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway • PennDOT has provided typical applications for self-managed stop control in short-term station- ary (see Figure 3-13) and long-term stationary (see Figure 3-14) 1L2W operations (PennDOT 2014). The STOP sign shall be visible for a minimum distance of E (see Table 3-10). If an existing passing zone is present, a no passing zone shall be established in long-term stationary operations using a NO PASSING ZONE sign and a temporary double yellow pavement marking line, as shown in Figure 3-14. Advance warning sign spacing and distances recommended by PennDOT are listed in Table 3-10. Shadow vehicles are utilized by TxDOT when self-managed control is used. For roadways without paved shoulders, TxDOT states that a shadow vehicle should be used if it can be posi- tioned 30 to 100 feet in advance of the work crew without lowering the performance or quality of work. If workers are not present, channelizing devices may be substituted for the shadow vehicle (TxDOT 2012a). Self-managed control is the least expensive traffic control method used in 1L2W operations. In addition to advance warning signs, self-managed control often includes YIELD or STOP signs to control traffic at the TTC zones. When a YIELD sign is used, it is most often placed on the closed lane approach. When STOP signs are utilized, the signs are often used in both directions. State DOTs utilizing self-managed control often deploy the control method in short TTC zones (less than 600 feet long) with low traffic volumes (less than 2,000 vpd). Sufficient sight distance is required. If traffic cannot regulate itself, a single flagger or another TTC method is necessary. AFADs AFADs are not commonly used in 1L2W operations. However, many state DOTs are consid- ering the use of AFADs, and Mississippi DOT and ADOT report frequent utilization of AFADs for 1L2W operations. The frequencies of AFAD deployment in 1L2W operations are shown in Figure 3-15. The most common factors in selecting AFADs for 1L2W operations are topography, length of closure, sight distance, and duration of work (short-term or long-term operation) (see Appen- dix C, Table C-5). AFADs are often utilized in short-term operations where length of closure is relatively short, and sight distance is sufficient. In accordance with MUTCD Section 6E.04, several state DOTs have developed policies/guidelines for AFADs: • FDOT requires AFADs to be positioned at places where they are clearly visible to oncoming traffic (FDOT 2017c). If AFADs have successfully passed AASHTO’s Manual for Assessing Safety Hardware crash test TL-3 criteria, they can be positioned on the centerline. When a single AFAD placed on a shoulder is utilized to control one direction of traffic, a gate arm is required. In Florida, a remotely controlled STOP/SLOW AFAD mounted on either a trailer or a movable cart system, or a remotely controlled Red/Yellow Lens AFAD may be used. AFADs may be used as a supplement or as an alternative to flaggers in accordance with plans, design standards, and vendor drawings (FDOT 2017c). • MoDOT states that AFADs shall not be utilized in long-term stationary operations. When AFADs are utilized in 1L2W operations in Missouri, MoDOT requires flaggers to have an unobstructed view to the AFAD and approaching traffic (MoDOT 2017). The maximum length between AFADs can be 0.5 miles. AFAD operators shall be trained as certified flaggers. A protective (shadow) vehicle may be positioned at least 150 feet in advance of the activity area. • VDOT allows AFADs only when all of the following conditions exist (VDOT 2015a): 1. The TTC zone is 1L2W. 2. There is only one lane in the direction to be controlled. 3. ADT is less than 12,000 vpd.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 55 Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. Attach red flashing lights on stop signs. 3. See Table 3-10 for spacing D. Figure 3-13. Pennsylvania typical application for self-managed stop control in short-term stationary operations (PennDOT 2014).

Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. Attach red flashing lights on stop signs. 3. See Table 3-10 for spacing D. 4. If a shadow vehicle is not present, 50 feet are measured from end of taper to beginning of work space. D Max Figure 3-14. Pennsylvania typical application for self-managed stop control in long-term stationary operations (PennDOT 2014).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 57 Speed (mph) D* (feet) E* (feet) H* (feet) 25 50 155 150 30 60 200 150 35 70 250 150 40 80 305 150 45 90 360 150 50 100 425 250 55 110 495 250 Source: (PennDOT 2014) *- Applicable to Figures 3-13, 3-14, 3-22 to 3-26, 3-31, 3-32, and 4-1 to 4-3. Table 3-10. PennDOT advanced warning sign distance and spacing reference. Figure 3-15. AFAD method deployment in 1L2W operations by state DOTs. 4. An unobstructed view of the AFADs and approaching traffic in both directions is available. 5. For multiple operators and closures greater than 800 feet, an engineer approval is required. VDOT also states that AFADs shall not be used as a substitute or replacement for a continu- ously operating TTCS. Consistent with other states, VDOT requires that AFADs be operated by certified flaggers. Shadow vehicles may be used with AFADs in 1L2W operations. Figure 3-16 shows a typical application for Red/Yellow lens AFADs provided by VDOT. Buffer lengths and spacing of advance warning signs recommended by VDOT are listed in Table 3-11 and Table 3-12, respectively. State DOT recommendations for using a single flagger to operate a pair of AFADs include the following: • In Florida, when a single AFAD is used, FDOT requires that the device be placed at one end of the TTC zone and a flagger be placed at the other end. A single flagger may operate two AFADs, or a single AFAD may be used if all of the following conditions exist (FDOT 2017c): 1. An unobstructed view of the AFAD(s) is available. 2. An unobstructed view of approaching traffic in both directions is available. 3. The distance between two AFADs or the AFAD and the flagger is less than 800 feet. 4. Two flaggers are available on site who can control traffic if an AFAD malfunctions.

58 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Notes: 1. Buffer lengths are listed in Table 3-11. 2. Sign spacing is provided in Table 3-12. Figure 3-16. Virginia: Red/Yellow lens AFADs (VDOT 2015a).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 59 • KDOT allows a single flagger to operate two AFADs when (KDOT 2015a): 1. An unobstructed view of the AFAD(s) is available. 2. An unobstructed view of approaching traffic in both directions is available. 3. The flagger can accurately read the AFADs’ indicators. • MnDOT allows a single flagger to operate two AFADs. When a single operator is used, the operator shall see both AFAD locations (MnDOT 2014). Figure 3-17 illustrates a typical appli- cation for AFAD operation in 1L2W TTC zones provided by MnDOT. • ODOT requires one AFAD operator per AFAD trailer for work zones on state highways (ODOT 2016b). ODOT disallows the use of AFADs when a single AFAD at one end of the work area is operated by a flagger who is simultaneously flagging traffic at the other end of the work area. A single flagger is not allowed to operate two AFADs. • VDOT allows a single operator to control two AFADs only if the operator has an unobstructed view of the AFADs and approaching traffic in both directions (VDOT 2015a). Costs of AFADs are handled in different ways. For example, AFADs in Florida are not paid for separately, and the cost for AFADs needs to be included in Maintenance of Traffic, Lump Sum (FDOT 2017c). In Kansas, AFADs may be used at the contractor’s discretion, and such use of AFADs in addition to flaggers will be subsidiary to other contract items and will not be paid for separately (KDOT 2015a). In Missouri, all TTC devices are paid for at the contract unit price for each of the pay items included in the contract, and no direct payment is made for AFADs (MoDOT 2016). AFADs have higher device costs and setup/removal times than flagger control. For short- term operations, contractors often prefer human flagger control due to these drawbacks of Posted Speed Limit (mph) Buffer Space (feet) 20 115–120 25 155–1651 30 200–210 35 250–260 40 305–3251 45 360–380 50 425–445 55 500–5301 60 570–6001 65 645–675 70 730–760 75 820–850 Source: (VDOT 2015a, VDOT 2015c) Note: 1. These distances should be increased for downgrades and other geometric conditions that affect stopping distance. Table 3-11. Buffer lengths provided by VDOT. Road Type Spacing (feet) Urban street with 25 mph or less posted speed 100–200 Urban street with 30 to 40 mph posted speed 250–350 All other roadways with 45 mph or less posted speed 350–500 All other roadways with greater than 45 mph posted speed 500–800 Limited-access highways 1,300–1,500 Source: (VDOT 2015a) Table 3-12. Spacing of advance warning signs provided by VDOT.

60 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Notes: 1. Approach signs are the same in both directions. 2. When the posted speed limit is 40 mph or less, the ONE LANE ROAD AHEAD sign may be removed. 3. The two-way taper should be 50 feet. 4. Flagger position when single operator is used. 5. Appropriate sign on the AFAD should be used. 6. A, B, and G distances are listed in Table 3-4. Figure 3-17. MnDOT typical application for AFADs in 1L2W operations (MnDOT 2018).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 61 AFADs. State DOTs have developed or are developing standard plans and guidelines for the use of AFADs. DOTs allow AFADs to be used when 1L2W TTC zones are up to 0.5 miles in length. A single flagger often can operate the devices if an unobstructed view of the AFADs and approach- ing traffic is available. TTCSs TTCSs are commonly utilized in 1L2W operations. TTCSs can be fixed support or portable (pedestal-mounted or trailer-mounted). The frequency of TTCS deployment in 1L2W opera- tions by state DOTs is shown in Figure 3-18. Indiana and South Carolina DOTs are the only two indicating that TTCSs are not utilized for their in-house operations. Length of closure, duration of work, sight distance, and topography are important factors con- sidered in selecting TTCSs for traffic control in 1L2W TTC zones (see Appendix C, Table C-6). TTCSs are often utilized in long-term and/or nighttime operations. The considerable effort required to set up and take down TTCSs makes them less suitable for short-term operations. Policies/guidelines recommended by state DOTs for the use of TTCSs include: • In Florida, when distance between signals is more than 0.5 miles, FDOT requires a combi- nation of manually controlled TTCSs and a pilot car to control traffic in 1L2W operations (FDOT 2017b). FDOT states that TTCSs are to be used only when workers are present so traf- fic can be controlled by flaggers when TTCSs malfunction (e.g., because of a power failure). Figure 3-19 illustrates a typical application for TTCSs in 1L2W TTC zones in Florida. This typical application is slightly different from the typical applications provided by other state DOTs. FDOT requires that traffic in the open lane perform a lane change maneuver as with a traffic chicane, when it is allowed to proceed. • Iowa DOT provides guidelines for equipment and operational requirements of TTCSs (Iowa DOT 2017). For actuated signals used in 1L2W operations, “green revert” and “rest in absence of actuation” should be applied. In “green revert,” during the All-Red clearance time (if used), if a vehicle is detected in the approach that is losing the right-of-way and there are no vehicles detected in the opposite direction, the All-Red clearance time should be terminated and the right-of-way should be reverted to the previous traffic phase. In “rest in absence of Figure 3-18. TTCS method deployment in 1L2W operations by the state DOTs.

Figure 3-19. Florida typical application for TTCSs (FDOT 2017b).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 63 actuation,” the right-of-way indication dwells in All-Red when there are no detected vehicles or recall switches. If an additional phase is utilized for a side road movement, there should be one long All-Red interval between active phases on each side of the work area. If TTCSs malfunc- tion, flaggers should be placed. At least two traffic signal heads should be used per approach. • KDOT allows TTCSs utilized in 1L2W operations to be left unattended if each approach is visible to the other (KDOT 2015c). When unattended TTCSs are not allowed, signals shall be manually operated, directly or by remote, by a trained flagger. KDOT requires that when TTCSs are utilized, all signals shall be capable of actuation. In Kansas, a single flagger is allowed to simultaneously operate multiple signals when: 1. An unobstructed view of the signals is available. 2. An unobstructed view of approaching traffic in each direction is available. 3. The flagger can accurately read the signals’ indicators (KDOT 2015a). • In Manitoba, Canada, Manitoba Infrastructure and Transportation has provided a typical application for TTCSs in roadways with more than 60 vehicles per hour (vph) and works longer than 4 hours (Manitoba 2015). The typical application includes several supporting advanced warning signs. • For maintenance operations in Missouri, MoDOT positions a protective (shadow) vehicle at least 150 feet in advance of the work space (MoDOT 2017). For construction operations, the protective vehicle is not required. Signal timing parameters are altered for each location. Stop bar shall be installed if the TTCS is in place for more than 3 days, and conflicting markings should be removed. For long-term operations, flags and an advance warning rail system (three barricade rails used to enhance the target value of certain signs) shall be used on advance signs. Figure 3-20 and Figure 3-21 illustrate typical applications for TTCSs in maintenance and con- struction 1L2W operations provided by MoDOT. Sign spacing and buffer lengths proposed by MoDOT are listed in Table 3-13. • PennDOT has provided typical applications for pedestal-mounted portable traffic control signals, trailer-mounted portable traffic control signals for conditions such as complex, non- complex, short-term, long-term, and manually controlled signals (PennDOT 2014). PennDOT defines a non-complex condition as a condition where driveways and/or side roads do not exist in the TTC zone. The minimum All-Red clearance interval and minimum signal face visibility distance required by PennDOT are listed in Table 3-14 and Table 3-15, respectively. The Penn- sylvania typical applications for short-term pedestal-mounted, short-term trailer-mounted, alternate trailer-mounted, long-term on fixed support, and long-term trailer-mounted TTCSs are shown in Figure 3-22, Figure 3-23, Figure 3-24, Figure 3-25, and Figure 3-26, respectively. In 2016, Caltrans conducted a cost analysis on human flagger control versus TTCSs. For flaggers in California, the prevailing wage was $51.24/hour. For 24 hours/day operations, three flaggers are required (one flagger provides relief). Therefore, cost of flagging (72 hours/day of flagging) without overtime shifts on weekends or extended shifts on weekdays (such as 12-hour shifts) is $3,689.00/day. The cost of flagging was $2,500.00/day when two flaggers per day were used, and relief was sent from work crew. For portable TTCSs, the rental rate for two signals was $6,000.00/month. The operational costs of TTCSs were not provided; however, it was concluded that the benefit-cost ratio for using a portable TTCS was positive. Caltrans’ conclu- sions were based on the assumption that flaggers are not required to operate TTCSs. In states that require flaggers to be present to operate TTCSs, the operational costs of TTCSs may increase. Survey questionnaire results indicated that TTCSs are being more frequently utilized by state DOTs. TTCSs can be on fixed support or trailer- or pedestal-mounted. Various signal control plans including pre-timed, actuated, or manual are currently being used. The maximum length of closure with TTCSs is often less than with pilot cars and human flagger control, which is mainly due to com- munication and excessive delay concerns. Communication and coordination of TTCSs becomes problematic in long 1L2W sections, especially if there are multiple traffic signals at side roads.

64 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Note: 1. S and B distances are listed in Table 3-13. Figure 3-20. Missouri typical application for signal control in maintenance operations (MoDOT 2017).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 65 Note: 1. S and B distances are listed in Table 3-13. Figure 3-21. Missouri typical application for signal control in construction operations (MoDOT 2017). Posted Speed Limit (mph) Sign Spacing (S) feet Buffer Space (B) feet 0–35 200 280 40–45 350 400 50–55 500 560 60–70 1,000 840 Source: (MoDOT 2017) Table 3-13. Missouri sign spacing and buffer lengths.

66 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Length (feet) Minimum All-Red interval (sec) Speed: 15 mph Speed: 20 mph Speed: 25 mph 1,000 45 34 27 950 43 32 26 900 41 31 25 850 39 29 23 800 36 27 22 750 34 26 20 700 32 24 19 650 30 22 17 600 27 20 16 550 25 19 15 500 23 17 14 450 20 15 12 Source: (PennDOT 2014) Table 3-14. PennDOT required minimum All-Red clearance interval. Normal Speed Limit (mph) Minimum Visibility Distance (feet) 25 215 30 270 35 325 40 390 45 460 50 540 55 625 Source: (PennDOT 2014) Table 3-15. Pennsylvania minimum signal face visibility distance. Pilot Car Pilot cars are commonly used by state DOTs in 1L2W operations. Pilot cars are used in con- junction with flaggers to help control traffic passing through 1L2W TTC zones. The goal of using pilot cars is to provide guidance to drivers on travel path and speed through the TTC zone. The frequency of pilot car deployment in 1L2W operations is shown in Figure 3-27. MassDOT and DelDOTs never use pilot cars for let-to-bid operations. Indiana and South Carolina DOTs never utilize pilot cars for in-house operations. For both in-house and let-to-bid operation, six state DOTs including Ohio, Vermont, Rhode Island, Tennessee, New Jersey, and Connecticut never use pilot cars for 1L2W traffic control. All other state DOTs responding to the survey questionnaire use some form of pilot car operations. Length of closure and sight distance are the most common factors when considering the use of pilot cars (see Appendix C, Table C-7). Pilot cars are often used in long TTC zones and help maintain vehicle speeds. In TTC zones with complex situations, where motorists might get con- fused, pilot cars are often utilized. State DOT policies/guidelines for utilizing pilot cars include the following: • ADOT requires that flagger stations and pilot car turn-around areas should be placed at loca- tions that provide the safest operations (ADOT 2010). Flagger stations and pilot car turn- around areas in rolling or mountainous terrain should be placed at the top and bottom of the grade, if possible. When there is a flagger station at the top of a grade, a brake check area should be established.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 67 Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. See Table 3-10 for spacing D. 3. For manual control, if an unobstructed view of both traffic traveling through the one-lane section and traffic on the approach to each portable traffic control signal unit is available, a single operator may be used. Otherwise, a separate operator is required at each signal unit, and communications between operators must be maintained. 4. In non-complex conditions: • A TTCS will control no more than two approaches to the work zone • No at-grade railroad crossing within the 1L2W section and within 300 feet of a TTCS • No roadway approach on a downgrade of 5% or more if the normal speed limit is greater than 35 mph • No intersections or uncontrolled commercial driveways within the 1L2W section. (a) (b) Figure 3-22. Pennsylvania typical application for a short-term pedestal-mounted TTCS (a) non-complex conditions and (b) complex conditions (PennDOT 2014).

(a) (b) Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. See Table 3-10 for spacing D. 3. For manual control, if an unobstructed view of both traffic traveling through the one-lane section and traffic on the approach to each portable traffic control signal unit is available, a single operator may be used. Otherwise, a separate operator is required at each signal unit, and communications between operators must be maintained. 4. In non-complex conditions: • A TTCS will control no more than two approaches to the work zone • No at-grade railroad crossing within the 1L2W section and within 300 feet of a TTCS • No roadway approach on a downgrade of 5% or more, if the normal speed limit is greater than 35 mph • No intersections or uncontrolled commercial driveways within the 1L2W section • ADT is 1,000 vpd or less and the length of 1L2W section is 1,000 feet or less. Figure 3-23. Pennsylvania typical application for a short-term trailer-mounted TTCS: (a) non-complex conditions and (b) complex conditions (PennDOT 2014).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 69 Note: 1. Optional signal configurations shall only be used when the primary configuration is unreasonable due to physical obstructions. Figure 3-24. Pennsylvania typical application for an alternate trailer-mounted TTCS placement (PennDOT 2014).

Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. See Table 3-10 for spacing D. Figure 3-25. Pennsylvania typical application for a long-term TTCS on fixed support (PennDOT 2014).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 71 Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. See Table 3-10 for spacing D. Figure 3-26. Pennsylvania typical application for a long-term trailer-mounted TTCS (PennDOT 2014).

72 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Figure 3-27. Pilot car method deployment in 1L2W operations by state DOTs. • When nighttime operations are conducted or when approaching vehicles cannot see from one flagger station to the other, ODOT states that pilot cars should be considered (ODOT 2016a). Depending on traffic volumes and roadway geometry, pilot car operation should be limited to 3 to 5 miles. Reliable communications such as radios shall be utilized between flaggers, pilot car and work superintendent or designated worker, at all times. No motorists should be allowed to pass the pilot car. ODOT states that pilot cars are effective for a variety of work types including striping operations, paving operations, complex temporary alignments, longitudinal excavations, shoulder work, and night work. Figure 3-28 shows a typical applica- tion provided by ODOT for pilot car operations in 1L2W TTC zones. Specifically, ODOT uses pilot cars when (ODOT 2016b) 1. The length of closure is greater than 0.5 mile and sight distance between flagger stations is obscured by a. Roadway topography/geometry—horizontal/vertical curvature, foliage. b. Geography—terrain that limits communication (cell coverage, radios, etc.). 2. Workers are immediately next to high-speed traffic that is not separated by a barrier system. 3. There are multiple isolated activities occurring within a single, longer TTC zone. ODOT limits the maximum length of TTC zones in pilot car operations based on (ODOT 2016b) 1. An operating speed of 25 to 30 mph. 2. Maximum allowable vehicle delay of 20 minutes. 3. Number of access points and intersections. • When pilot cars are used in Kansas, flaggers or AFADs with flaggers should be available (KDOT 2015a). Pilot car operations should be maintained continuously without causing additional delays to motorists for reasons such as breaks or refueling. Pilot cars should coordinate the work and should not be used for other purposes. The contractor’s company logo and contact information should be displayed on pilot car vehicles. The maximum speed of pilot cars in TTC zones is 40 mph. In the vicinity of workers, speeds should be restricted to 20 mph. • MnDOT states that all vehicles should follow the pilot car and remain in a tight group to prevent motorists from separating (MnDOT 2014). If the last car in the group has proceeded more than 300 feet from the flagger station, the flagger should not allow additional vehicles to proceed to keep the traffic tight.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 73 Notes: 1. A, B, and C distances are listed in Table 3-16. 2. The PILOT CAR FOLLOW ME sign is MUTCD G20-4 sign. Figure 3-28. Oregon typical application for pilot car operation in 1L2W TTC zones (ODOT 2016b).

74 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway • The Nebraska DOT requires pilot cars to make a round trip in 15 minutes or less (NDOR 2007). Pilot cars shall be used exclusively to lead and assist traffic movements. Pilot cars shall operate continuously and avoid delays to motorists due to refueling, driver relief, etc. Pilot car drivers shall be certified flaggers and shall be properly licensed. The drivers are subject to prosecution for all violations. • The Nevada Department of Transportation (NDOT) requires a 30 MINUTE DELAY POSSIBLE sign to be placed in advance of the closure (NDOT 2017). Pilot cars are frequently used by state DOTs especially when the work area is long and com- plex, sight distance is limited, or it is critical to maintain a desirable vehicle speed within a 1L2W section. The MUTCD requires flaggers to be present when a pilot car is utilized. Reliable com- munications should be utilized between flaggers and the pilot car operator. Other The DOTs in states such as Connecticut and Rhode Island use law enforcement to help con- trol traffic in 1L2W operations. Massachusetts is the only state that controls traffic in 1L2W TTC zones with a police detail. Most traffic control in 1L2W TTC zones in Massachusetts is conducted by law enforcement, and standard flaggers are not available. Until 2008, MassDOT was required by law to use police details in 1L2W operations. Human flagger control was allowed in Massachusetts when a regulation (701 C.M.R. § 7.00) went into effect on October 3, 2008. Very few areas in Massachusetts may use flaggers for controlling traffic. The effective- ness of police details in comparison to standard human flagger control for providing safe and efficient operations has not been evaluated due to limited human flagger control experience in Massachusetts. Side Road and Driveway Treatment Numerous driveways and side roads can add challenges to the overall traffic control plan in TTC zones. Policies/guidelines provided by state DOTs for treating side roads and driveways in 1L2W TTC zones include the following: • In 1L2W TTC zones with several side roads or driveways, a pilot car shall be used in Cali- fornia. Caltrans’ mandatory pilot car utilization is not included in the written documents. When a pilot car is used, a TRAFFIC CONTROL—WAIT AND FOLLOW PILOT CAR sign Posted Speed (mph) Spacing Between Signs (feet) Buffer Space (feet) A B C 20 100 100 100 50 25 75 30 100 35 350 350 350 125 40 150 45 500 500 500 180 50 210 55 250 60 700 700 700 285 65 325 70 365 Source: (ODOT 2016a) Table 3-16. ODOT sign spacing and buffer lengths.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 75 should be placed at all intersections, driveways, and alleys. The supplementary sign is not a standard MUTCD sign, and it is not included in the MUTCD. If traffic cannot be effectively self-managed, at least one flagger shall be used at each intersection within a 1L2W work area (Caltrans 2015). • FDOT states that signing for the control of traffic at intersections shall be adequate to inform motorists of TTC zone conditions (FDOT 2017a). The ROAD WORK AHEAD sign should be placed on side streets if work operations exceed 1 hour. Figure 3-29 shows Florida typical applications for side road control when TTCSs are used. Vehicles traveling in the open lane of the main road should perform a crossover maneuver. • KDOT places flaggers at all highway and major collector intersections and at-grade railroad intersections (KDOT 2015a). At minor side road intersections, a flagger may be used. When a pilot car is used, a WAIT FOR PILOT CAR sign shall be positioned at side roads. • MDOT requires flaggers to be placed at intersecting roads and/or significant traffic generators (mobile home parks, shopping centers, etc.) (MDOT 2010a). Flaggers at side road intersections within the TTC zone are responsible for controlling traffic movements. MDOT requires that flaggers 1. Use a STOP/SLOW paddle. 2. Be in radio or visual contact with other flaggers. 3. Do not stop the mainline flow of traffic. 4. Allow traffic to proceed in either direction after the mainline flow of traffic passes their station. 5. Inform other flaggers about the last vehicle added to the traffic flow in each direction. 6. Be positioned at a location close to the intersection with a clear view to traffic in all direc- tions and with an ability to safely stop motorists at the intended stopping point. • MDT states that when a TTCS is used for 1L2W traffic control, side approach traffic should be incorporated by using TTCSs, devices, etc. (MDT 2014a). • NDOT requires a WAIT FOR PILOT CAR sign to be placed at side roads in Nevada. Placing a 30 MINUTE DELAY POSSIBLE sign at side roads is optional (NDOT 2017). • ODOT requires human flagger control when the TTC zone is short and there is one side road. If there is more than one side road and the TTC zone is long, pilot car operations are used. When pilot cars are used, the WAIT FOR PILOT CAR sign may be used on side roads or access when the following conditions are met (ODOT 2016a): 1. The access or side road is a dead-end facility or has no immediate alternate access, does not access public service facilities (e.g., utility hubs, parks, treatment plants, rest stops, landfills, waysides, ranger stations, etc.), and has ADT of less than 100 vpd. 2. The additional delay for side road traffic is less than 20 minutes. When side road traffic volumes are between 100 vpd and 400 vpd, a pilot car sign may be used only if traffic compliance, operation, and safety are frequently checked and monitored. If operational issues are observed, the pilot car sign should be replaced by flaggers or other traffic control methods (ODOT 2016a). • WSDOT states that side roads and approaches should be closed or controlled by a flagger or by proper approved signing (WSDOT 2016a). If there is a line of sight between the side road and end flaggers, flaggers should coordinate the movements. If the end flagger cannot be seen from the side road flagger station, a pilot car should be used. Figure 3-30 shows a typical application provided by WSDOT for side road treatment in 1L2W operations when human flagger control is utilized. Sign spacing and buffer lengths recommended by WSDOT are listed in Table 3-17 and Table 3-18. When side roads intersect with 1L2W TTC zones, state DOTs require additional traffic con- trol devices and proper signs to be placed at the side roads. Traffic control methods utilized at side roads include self-managed, flagger, TTCS, and pilot car.

Figure 3-29. Florida typical applications for side road treatment (FDOT 2017a).

Notes: 1. Sign spacing (X) is listed in Table 3-17. 2. Buffer lengths (B) are listed in Table 3-18. Figure 3-30. Washington State plan for side road operations with flaggers (WSDOT 2016b).

78 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway End-of-Queue Management End-of-queue management is primarily performed using additional advance signs or increas- ing sign spacing. When traffic queues extend beyond initial advance warning signs, extended queue signing is utilized in states including California, Oregon (ODOT 2016a), and Colorado (CDOT 2016). Also, advance warning signs are utilized when sight distance is limited (FDOT 2017a). The advance flagger method also has been used to manage the end of queues. In Minnesota, MnDOT requires flaggers to observe traffic back up distances during flagging operations. If the traffic back up distance is long, the flaggers should notify their immediate supervisor for instructions on how to maintain shorter vehicle queues (MnDOT 2014). The defi- nition of “long” and what instructions and flagger methods were used to reduce the queue length were not provided. In Montana, MDT recommends that when more than 10 motorists are stopped at a flagging sta- tion 50% of the time, a second flagger should be provided to inform traffic of the delay. An additional sign should be placed 500 to 1,000 feet in advance of the end of the vehicle queue (MDT 2014b). Mandatory Use of PCMSs Percentages of state DOTs that have mandated the use of PCMSs in work areas are listed in Table 3-19. For instance, in California, Caltrans requires PCMSs per Special Provisions and they are used in advance of the first sign for each closure in each direction of travel. Project Coordination When there are multiple 1L2W TTC zones in close proximity, they should be coordinated to ensure efficient and safe operations. Survey questionnaire results for project coordination guidelines developed by state DOTs are listed Table 3-20. Type Speed (mph) Sign Spacing (feet) RURAL HIGHWAYS 60 and 65 800 ± RURAL ROADS 45, 50, and 55 500 ± RURAL ROADS & URBAN ARTERIALS 35 and 40 350 ± RURAL ROADS, URBAN ARTERIALS, RESIDENTIAL & BUSINESS DISTRICTS 25 and 30 200 ± URBAN STREETS 25 100 ± Source: (WSDOT 2016b) Table 3-17. WSDOT sign spacing. Speed (mph) 25 30 35 40 45 50 55 60 65 70 Length (feet) 155 200 250 305 360 425 495 570 645 730 Source: (WSDOT 2016b) Table 3-18. WSDOT buffer lengths. Operation Yes No Number of Responses In-house 10% 90% 10 Let-to-bid 8% 92% 12 Let-to-bid & In-house 29% 71% 31 Table 3-19. Mandatory use of PCMSs.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 79 For projects in close proximity, California requires a dedicated Traffic Manager to be assigned to coordinate the closures to maximize throughput and minimize traffic delays. Vermont and Georgia DOTs require the distance between consecutive lane closures to be at least 1 mile (VTrans 2011, GDOT 2012). Special Roadway Geometrics In unique situations such as intersections and roundabouts, 1L2W traffic control requires appropriate guidelines. This section describes reported policies/guidelines for 1L2W traffic con- trol at special roadway geometries. Intersections Policies/guidelines provided by state DOTs for 1L2W traffic control at intersections include the following: • The Colorado Department of Transportation (CDOT) suggests considering closing one or more of the intersection approaches (CDOT 2013). When closing approach(s) is impractical, through vehicular traffic should be directed to other roads or streets. Flagger(s) or uniformed law enforcement, depending on conditions, should be utilized at intersections. • DelDOT states that when work is performed in an intersection that creates the need to over- ride the existing traffic control, a minimum of one flagger shall be placed at each intersection approach. An additional flagger as the primary flagger may be provided. When the primary flagger is used, the primary flagger shall control the traffic and direct the actions of the other flaggers. On roadways with ADTs of more than 2,000, the operations shall be coordinated with DelDOT’s Traffic Safety Section. The approach flaggers are required to monitor queue lengths and shall provide operations with minimal practicable delay (DelDOT 2012). • The Georgia Department of Transportation (GDOT) states that when lane closures at inter- sections occur that prevent the actuated traffic signal from guiding the traffic, off-duty police officers shall be used (GDOT 2012). • The Indiana Department of Transportation (INDOT) has provided various plans for 1L2W operations under various conditions, including short duration (less than 1 hour), short-term stationary (1 to 12 hours), works in advance of an intersection, works beyond an intersection, and works at the side of an intersection. • For 1L2W operations at intersections in Oregon (ODOT 2016a) 1. Traffic signals shall be turned off during flagging operations. 2. When there are multi-lane facilities, those approaches shall be reduced to a single lane. 3. One flagger should be located at each approach. When intersection traffic volume is less than 400 vpd, a single flagger may be used. 4. It is optional to use ONE LANE ROAD AHEAD sign. This sign should be considered when traffic volumes are high, roadway speed is high, or when queues may extend. • PennDOT has provided typical applications for short-term stationary 1L2W traffic control at three-leg (see Figure 3-31) and four-leg (see Figure 3-32) intersections (PennDOT 2014). Operation Yes No Number of Responses In-house 20% 80% 10 Let-to-bid 42% 58% 12 Let-to-bid & In-house 42% 58% 31 Table 3-20. Project coordination guidelines developed by state DOTs.

80 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. For operations of 15 minutes or less: (a) the ROAD WORK, ONE LANE ROAD, BE PREPARED TO STOP, and flagger symbol signs are not required, and (b) if a shadow vehicle is present, channelizing devices may be eliminated. 3. See Table 3-10 for distance and spacing (D, E, and H). 4. If a shadow vehicle is not present, distance E is measured from end of taper to beginning of work space. Figure 3-31. Pennsylvania typical application for three-leg intersection flagging (PennDOT 2014).

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 81 Notes: 1. For rural roadways, suggested spacing of advance warning signs (A, B, and C) is 500 feet. 2. For operations of 15 minutes or less: (a) The ROAD WORK, ONE LANE ROAD, BE PREPARED TO STOP, and flagger symbol signs are not required, (b) if a shadow vehicle is present, channelizing devices may be eliminated. 3. See Table 3-10 for distance and spacing (D, E, and H). 4. If a shadow vehicle is not present, distance E is measured from end of taper to beginning of work space. Figure 3-32. Pennsylvania typical application for four-leg intersection flagging (PennDOT 2014).

82 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway In the typical applications, a flagger is stationed at the center of the intersection. It is stated that each flagger shall be clearly visible for a minimum distance of E (see Table 3-10), each flagger shall be in constant communication with all other flaggers, and the buffer space shall be extended to provide adequate sight distance in horizontal or vertical curves. Roundabouts Roundabouts are becoming more common across the United States, and several state DOTs have developed typical TTC applications for 1L2W operations at roundabouts. These typical applications are discussed in greater detail as a case example in Chapter 4. Proper guidelines and policies are needed to control 1L2W operations in unique situations such as intersections and roundabouts. States DOTs including Delaware, Indiana, Oregon, and Pennsyl- vania use flaggers to control traffic in 1L2W TTC zones at intersections. At signalized intersections in Georgia, when lane closure prevents the actuated traffic signal from guiding traffic, off-duty police officers are used. The number of required flaggers and the position of the flaggers vary among DOTs. The location of the flaggers also varies. In Pennsylvania, a flagger is stationed at the center of the intersection while other state DOTs position the flaggers only on the approaches. Speed Control Methods PCMSs and TPRSs are the most common speed control methods used by state DOTs in 1L2W operations. Results of the survey questionnaire for these two methods are listed in Table 3-21. Further information on current speed control methods is provided in NCHRP Synthesis 482: Work Zone Speed Management (Shaw et al. 2015). ITSs ITSs such as variable speed limits (VSL), queue warning, and automated enforcement are rarely used in 1L2W operations. The most common ITS utilized in 1L2W TTC zones is the real- time traveler information system (e.g., 511 system). Some state DOTs, including FDOT, require work crews to feed real-time traveler information systems during work activities. Summary Information on current organization practices regarding 1L2W operations in rural highway TTC zones was obtained using a survey questionnaire distributed to transportation organiza- tions through the AASHTO Subcommittee on Construction. Responses from 45 state DOTs and 3 Canadian transportation organizations were received. Method Operation Yes No Number of Responses PCMS In-house 55% 45% 11 Let-to-bid 46% 54% 13 Let-to-bid & In-house 55% 45% 31 TPRS In-house 45% 55% 11 Let-to-bid 31% 69% 13 Let-to-bid & In-house 53% 47% 30 Table 3-21. PCMS and rumble strip methods utilized by state DOTs.

Survey Questionnaire and Interview Summary: An Overview of the Current State of Practice 83 Survey questionnaire results indicated that human flagger control is the most common traffic control method utilized in 1L2W operations among the state DOTs, while advance flaggers, flag transfer, self-managed, and AFADs are not frequently utilized. Pilot cars and TTCSs are commonly used by state DOTs. Information on current organizational practices in 1L2W operations including typical applications, design thresholds, applica- tions in special roadway geometries, and traffic analysis were obtained from the state DOTs and presented.