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

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1 Maintenance or construction operations on two-lane two-way roadways may require temporary closure of one of the traffic lanes to conduct work operations. When a single lane on a two-lane two-way roadway is closed, One-Lane Two-Way (1L2W) movement through the one-lane section is required. Various temporary traffic control (TTC) methods can be utilized for 1L2W movements. The primary objective of this synthesis was to identify practices and devices used for establishing 1L2W traffic control on rural two-lane highways. Specifically, this synthesis sought to identify practices and lessons learned in many areas, including construction versus maintenance activities, day and nighttime operations, length of lane closures, delay and other operational impacts, treatments for side roads and driveways, corridor management of work zones, and innovative devices used to support 1L2W operations. Information and data were gathered through a literature review as well as a questionnaire- style survey of the U.S. state departments of transportation (DOTs) and Canadian province DOTs. The survey questionnaire was distributed through the AASHTO Subcommittee on Construction. Responses were obtained from 45 state DOTs and 3 Canadian transportation organizations representing Manitoba, Northwest Territories, and Ontario. TTC is critical to minimizing congestion and maintaining mobility during planned and unplanned lane closure activities as well as providing a safe environment for both the road users and workers. During 1L2W operations, TTC plans are required to provide safe and efficient traffic movements through and around TTC zones. Part 6 of the Manual on Uniform Traffic Control Devices (MUTCD) is the U.S. national standard for all TTC devices used during activities such as construction, maintenance, utility, and incident management (FHWA 2009). The MUTCD provides standards, typical applications, and guidelines for 1L2W operations. Some state DOTs have developed practices to supple- ment the MUTCD standards. Vast experience related to one-lane traffic control on rural two-lane highways exists. TTC plans in 1L2W operations can be prepared by using some or all of the following methods: • Human flaggers: traffic may be controlled by either a single flagger or by a flagger at each end of the one-lane section. • Human flaggers with advance flaggers: advance flaggers are positioned at some distance upstream of TTC zones to warn approaching traffic of slow or stopped vehicles ahead. • Flag transfer: the driver of the last vehicle proceeding into the one-lane section is asked to transfer a red flag (or another token) to the flagger at the other end to signify it is safe for the human flagger to reverse the flow of traffic in the open lane. S U M M A R Y Practices in One-Lane Traffic Control on a Two-Lane Rural Highway

2 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway • Automated flagger assistance devices (AFADs): these consist of portable traffic control devices used by flagging personnel to control traffic during 1L2W operations. • Self-managed control: traffic is regulated using STOP and/or YIELD signs at the point where the single-lane operation begins. • Temporary traffic control signals (TTCSs): 1L2W operations are controlled using traffic control signals. • Pilot car operations: a pilot vehicle is used to lead a queue of vehicles through the single-lane section. Note that several of these methods, including pilot car operations, AFADs, flag transfer, and advanced flaggers require human flaggers or another TTC method to be present; thus, these methods are not independent. A comprehensive literature review was conducted to identify published information on 1L2W traffic control practices and procedures. The literature was clear in showing that human flagger control methods are widely deployed in 1L2W operations. Flaggers provide efficient traffic control in 1L2W TTC zones; however, the exposure of flaggers to traffic raises concerns about worker safety. To improve public and flagger safety in 1L2W TTC zones, TTC plans are often supplemented by using different devices such as temporary portable rumble strips (TPRSs) and portable changeable message signs (PCMSs). These devices are intended to inform drivers of a TTC zone ahead where they may be required to slow or stop. Comprehensive evaluations of advance flaggers, flag transfer, and self-managed control methods were missing in the literature. Several studies have evaluated the effectiveness of AFADs in 1L2W operations. Although some studies report noncompliant drivers, AFADs reduce or eliminate the exposure of flaggers to traffic and improve safety. TTCSs and pilot cars are extensively studied in the literature. TTCSs can be effective in supplementing flag- ger operations and controlling other work zone access points. Pilot car operations have been found effective in maintaining safe vehicle speeds and guiding motorists through complex TTC zones. Information on current organization practices regarding 1L2W operations in rural highway TTC zones was obtained using a survey questionnaire. After a comprehensive review of the survey questionnaire by the Topic 48-11 panel, pilot survey questionnaire tests among panel members were completed, and the survey questionnaire was distrib- uted to state DOTs and Canadian transportation organizations through the AASHTO Subcommittee on Construction. The list of survey questionnaire recipients was further augmented by inviting FHWA TTC zone contacts to assist in identifying appropriate state DOT representatives. Responses from 45 state DOTs and three Canadian transportation organizations were received. Following the review of survey questionnaire results from responding organiza- tions, DOTS in California, Florida, Kansas, Massachusetts, Michigan, Oregon, and Rhode Island were identified for telephone interviews to obtain additional and more detailed information together with case examples or other documents related to current practices. The survey questionnaire was broken into three sections pertaining to how work zone operations were managed: (1) let-to-bid operation procedures, (2) in-house operation pro- cedures, and (3) joint let-to-bid and in-house operation procedures. Nearly all responding DOTs noted that they use both bid operations and in-house operations. Only Delaware, Massachusetts, and Wisconsin DOTs reported that they perform 1L2W operations only with contractors. Mississippi DOT was the only state that uses only in-house staff to per- form 1L2W traffic control. Of the 41 states that perform both in-house and let-to-bid opera-

Summary 3 tions, approximately 25% (10 states) of the DOTs reported different policies or standards for the two types of operations. Survey questionnaire results indicated that human flagger control is the most common traffic control method utilized in 1L2W operations. Advance flaggers, flag transfer, and self- managed controls are not as frequently utilized. In fact, California and Texas DOTs have removed the flag transfer method from their guidelines due to the potential safety issue of drivers who do not hand in the flag at the other end and, consequently, prevent flaggers from communicating efficiently and safely. Self-managed control methods have been uti- lized in TTC zones with short closure length and very low traffic volumes. AFADs are not commonly used by state DOTs. One of the primary reasons noted for lim- ited deployment is that AFADs, in comparison to human flagger control, require additional devices, which increase project cost. Deployment of AFADs may not reduce labor cost in comparison to human flagger control since at least one flagger is required on site to operate the devices. For short-term operations, contractors often prefer human flagger control due to higher setup and removal times of AFADs. The MUTCD states that a state or local agency should adopt a detailed policy before using AFADs. Florida, Kansas, Minnesota, Missouri, Oregon, and Virginia DOTs have developed plans and guidelines for the use of AFADs. Pilot cars and TTCSs are frequently used by state DOTs. When it is critical to maintain a desirable vehicle speed within a 1L2W section, or when the work area is long and complex, pilot car operations are often utilized. When multiple side roads exist within 1L2W TTC zones, several states require pilot car deployment. TTCSs are suitable for longer term opera- tions. Long setup and removal time as well as high equipment costs make the TTCSs a less preferred method in shorter term 1L2W operations. Law enforcement is used to help flaggers control traffic in 1L2W operations, especially in the New England states. For example, Massachusetts DOT typically utilizes law enforcement details to flag traffic in 1L2W TTC zones. Until 2008, Massachusetts DOT was required by law to exclusively use police details in 1L2W operations. Non-law-enforcement flagger con- trol was first allowed in Massachusetts in 2008 for low-speed (less than 45 miles per hour) and low-volume roadways. Over 66% of the reporting state DOTs use design criteria such as maximum length of clo- sure, maximum traffic volumes, maximum target vehicle delays, and maximum speed limit for selecting the traffic control method in 1L2W operations. Maximum length of closure allowed by state DOTs varied greatly—between 100 feet and 4 miles—depending on the traf- fic control method employed. Single flagger and self-managed controls have lower distance thresholds, while pilot car and flagger control (one flagger at each end) have greater distance thresholds. Maximum lengths of closure with TTCSs are often less than maximum lengths of closure with pilot cars and human flagger control; this is mainly due to communication and excessive delay issues. Communication and coordination of TTCSs become problematic in long 1L2W sections, especially if there are multiple traffic signals at side roads. If the length of closure is long and pre-timed signal control is used, unacceptable vehicle delays may occur. Maximum allowable targeted vehicle delays vary between 5 and 30 minutes. Capacity and vehicle delays in 1L2W TTC zones are often determined using the Highway Capacity Manual (HCM) methodology (TRB 2010). Several state DOTs, including Oregon and Michigan DOTs, use additional software programs for calculating capacities and vehicle delays in 1L2W TTC zones. Oregon DOT utilizes a web-based software program to con- duct work zone traffic analysis (WZTA). The web-based WZTA tool provides lane closure restrictions and delay estimates resulting from construction, maintenance, utility work, or incident management. Michigan DOT uses a software tool called Construction, Congestion,

4 Practices in One-Lane Traffic Control on a Two-Lane Rural Highway Cost (CO3) to estimate the magnitude and impacts of traffic congestion during a construc- tion project. State DOTs frequently use a combination of self-managed control, flagger, and TTCSs to control traffic on side roads within a single-lane TTC zone. When traffic volumes are low, self-managed control may be used. If traffic cannot be effectively self-managed, often flag- gers are utilized at side roads. When TTCSs at side road intersections are used, these signals are coordinated with signals located at both ends of a 1L2W section. Deploying 1L2W traffic control at intersections is discussed in guidelines provided by several state DOTs. Delaware, Indiana, Oregon, and Pennsylvania DOTs, among others, use flaggers to control traffic in 1L2W TTC zones at intersections. At signalized intersections in Georgia, when lane closure prevents an actuated traffic signal from controlling traffic, TTC by off-duty police officers is required. The number of required flaggers and the position of flaggers within the intersection vary among state DOTs. For example, a flagger is often stationed at the center of the intersection in Pennsylvania, while Delaware, Indiana, and Oregon DOTs position the flaggers only on the approaches. Roundabouts are becoming more common across the United States. Necessary TTC lane closures in roundabouts are not uniformly designed, as only four state DOTs reported having developed typical applications of 1L2W operations and TTC applications at roundabouts, and all four use only human flagger control. Handling different roundabout configurations, proper design thresholds, and managing vehicles that make a complete circle require further investigation. In a similar way, the application of TTC devices, such as the use of TPRSs in 1L2W opera- tions, are increasing. Developed typical applications for TPRSs in 1L2W operations vary in terms of the location of TPRSs and conditions for their use. Experiments with novel TTC devices have been tested to control traffic at access points and driveways within 1L2W TTC zones. Texas DOT tested driveway assistance devices (DADs) such as modified hybrid devices and blank-out sign devices to regulate traffic entering from low-volume access points. Michigan DOT started testing DADs in 2015, but no reports have been published. DADs have been tested in New Jersey and North Carolina as well. DAD experiments across the United States indicate that proper standards and guidelines for designing and implementing the devices have not been developed. The devices tested in Texas, North Carolina, Michigan, and New Jersey vary in terms of supple- mentary signs and direction indicators. Sufficient field data to evaluate the effectiveness of the devices in regulating traffic are required. Location of the devices, managing existing signs and traffic control devices, and understanding driver behavior when DADs are uti- lized require further investigation. Other states, including Florida and Massachusetts, are in early stages of testing DADs. Moving forward, the safety of 1L2W traffic control methods when utilized under different conditions (e.g., different traffic volumes and various lengths of closure) requires additional research. Various combinations of 1L2W traffic control methods such as utilizing pilot cars with TTCSs or AFADs where a pilot car driver can control TTCSs or AFADs also require further investigation. Traffic control for 1L2W operations in roundabouts requires further study to evaluate different traffic control methods, handle various roundabout configura- tions, determine proper design thresholds, and manage vehicles that make a complete circle. With regard to DADs, the effectiveness of the devices, location of the devices, management of existing signs and traffic control devices, and drivers’ behavior need to be explored.