Mobile operations on two-lane two-way roadways present unique problems due to highly variable conditions which are encountered in the field. Variables include the number of vehicles in the work convoy, travel speed of work vehicles, posted speed, roadway geometrics, and average daily traffic on the roadway. Highway agencies are challenged with developing temporary traffic management control (TTC) standards that ensure safe and efficient operations under these highly variable conditions, and consider the safety and mobility of road users.
Workers face many hazards during mobile operations on two-lane roadways. Many of these hazards are a direct result of the fact that motorists do not know how to properly react when encountering a work convoy. Examples of problematic motorist behavior include misunderstanding of traffic control devices, impatience with the delay caused by the slower speed of the mobile operation, inattention, speeding, and entering the convoy.
Temporary traffic control for most mobile operations has been limited to arrow panels and static warning signs mounted on the back of work vehicles. These devices often do not convey sufficient information to the motorist for them to make informed decisions. The truck mounted changeable message sign (TMCMS) is a technology that can improve driver understanding of specific hazards and desired responses to various mobile operations.
TTC for most mobile operations (as shown in Typical Application 17 in MUTCD Figure 6H-17) has historically been limited to a shadow vehicle with an arrow board in caution mode and/or a static sign with legend appropriate for the type of work. These devices often do not convey sufficient information for motorists to make informed decisions (such as when and if it is safe to pass the convoy). There is a need to enhance communication with motorists and provide more positive control of traffic in both directions during mobile operations on two-lane roadways. It is likely that this could be accomplished with the addition of flaggers at each end of the mobile operation to provide periodic passing opportunities for motorists.
Some state departments of transportation have developed enhanced motorist information systems for mobile operations on two-lane roadways. Wyoming DOT uses truck-mounted changeable message signs to relay information about the type of operation and the number of work vehicles involved. Texas DOT uses static CW21-10T signs to communicate how many work vehicles are in the operation. Research sponsored by Texas DOT investigated the use of truck-mounted changeable message signs to communicate information related to passing the work vehicles (i.e., DO NOT PASS, PASS WITH CARE, PASS ON SHOULDER, etc.) but ultimately found that implementation would be difficult because of constantly changing conditions that are inherent to mobile operations. In addition, it would be unwise to grant motorists permission to pass the convoy via changeable messages without fully controlling traffic coming from the opposite direction in the open lane. Other research sponsored by California DOT found that work zone intrusion crashes were caused by motorists entering the convoy (25%); rear-end crashes with a slower vehicle (25%); motorists striking work vehicle when passing (38%); and motorists swerving to avoid an adjacent crash (12%). The proposed research would address the issue of removing opportunities for motorists to make poor decisions by providing adequate opportunities for passing while controlling traffic in both directions.
The objective of this research is to develop TTC alternatives for mobile operations on two-lane roadways. Develop recommendations on communicating information to the motoring public in a manner that is well understood. The work zone devices used in the application should balance safety with the constant movement and/or stop-and-go nature of the work operation.
Possible research tasks may include the following:
- Develop Work Plan
- Summarize State-of-the-Practice
- Develop TTC Alternatives
- Evaluate TTC Alternatives
- Develop Recommendations
- Prepare Project Report