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17 4.0 Selection of Treatments for Field Evaluations The list of treatments for field evaluations were identified based on a combination of past research, state survey responses, and input from panel members. This section discusses the initial and final methodology used to select the treatments for field evaluations. 4.1. Initial List of Treatments The FHWA has identified approximately 100 work zone strategies that represent the three main TMP areasâTTC, public information, and TO. It would be ideal to conduct evaluations and/or case studies of all work zone strategies, but of course, this is not practical for any one project. To narrow the strategies for possible field evaluations, it was first necessary to eliminate strategies that had already proved effective or for which a general evaluation is not possible. Several strategies fall within these groups as listed below: â¢ Strategies that are mandated by the 2009 MUTCD or state laws (traffic control devices). â¢ Strategies that are already proven effective or where a wealth of information is currently available (e.g. dynamic speed message signs, portable message signs, night work). â¢ Strategies that cannot be quantitatively evaluated to document the effect on safety or mobility (e.g. social media, project website, real-time video display, freight travel information). â¢ Strategies that are highly specific to a particular location (or specific to the system deployed) and are therefore non-transferrable (e.g. park-and-ride promotion, shuttle services, ITS for traffic monitoring). â¢ Strategies that are dependent on the legislature in that particular state/agency (e.g. automated enforcement, warning lights). â¢ Strategies whose use in work zones could not be found (e.g. High-occupancy vehicle [HOV] lanes, toll/congestion pricing). As noted above, the team focused on a smaller subset of strategies as possible options for field evaluations. This smaller subset was then combined with practitioner survey input and available literature to identify potential treatments for field evaluation. Table 2 highlights the strategies that were explicitly considered. The effectiveness of past research is broken down into high, medium, and low. High previous research indicates more than five past studies, medium is between three and five, and low indicates a single study or none at all. Of the top 27 strategies identified in Table 2, the team determined that 12 strategies were already sufficiently addressed in the literature. The items eliminated from further consideration for Phase II are marked as high previous research in Table 2. Other strategies were found to have research gaps, but study design considerations make it infeasible to assess those strategies effectively as part of this effort. These include:
18 â¢ Literature/instances of the use of HOV lanes and toll/congestion pricing under work zone conditions is nonexistent. â¢ Temporary traffic signals for lane merge control on highways is a theoretical concept and requires considerable research prior to their real-world application. â¢ Although the intrusion alarms system can ideally alert workers when any vehicle intrudes into their work zone, the problems with these systems are evident and numerous. The workers and/or flaggers are unlikely to be able to hear an audible warning over the noise. Also, at issue was the number of times a system could be unnecessarily activated (false positive). Such false positives have the potential to cause workers to ignore the system altogether, thus negating the point of having it as a warning system. Another shortcoming is that some systems use a single detector upstream from the work zone and, thus, it is possible for vehicles to enter the work zone without activating the detector (a false negative). Furthermore, the heat and noise level produced by work zone equipment and vehicles passing by have been shown to interfere with infrared and ultrasonic detectors, again, also causing false positives. The few states that have experimented with intrusion alarms have all reported unreliable performance. â¢ Using automated enforcement in work zones requires state legislation. Currently, only a few states implement ASE programs in work zones and evidence of the programâs effectiveness is widely available. 4.2. Initial List of Treatments Identified for Field Evaluation Based on the above criteria, the team presented the following seven strategies as possible options for field evaluations. The strategies are listed below (in no particular order): â¢ Dynamic Lane Merge System. â¢ Ramp Metering. â¢ Reversible Lanes. â¢ Truck Lane Restrictions. â¢ Variable Speed Limits (VSL). â¢ Temporary Rumble Strips. â¢ Sequential Warning lights. â¢ Queue Warning System.
19 Table 2. Summary of Strategies Considered for Field Evaluation. Strategy Area Strategy Type Previous Research1 Survey Recommended Final Team Recommendation High Medium Low Transportation Demand Management (TDM) 1. Transit service improvements X 2. Transit incentives X 3. Shuttle services X X 4. Ridesharing/carpooling incentives X 5. Park-and-ride promotion X X 6. HOV lanes X 7. Toll/congestion pricing X Corridor/ Network Management Strategies 8. Dynamic lane closure system X X ï¼ 9. Ramp metering X ï¼ 10. Temporary traffic signals X 11. Truck lane restrictions X X ï¼ 12. Reversible lanes X X ï¼ Work Zone Safety Management Strategies 13. Speed limit reduction X 14. VSL X X ï¼ 15. Movable traffic barrier systems X 16. Temporary rumble strips X X ï¼ 17. Intrusion alarms X 18. Sequential warning lights X ï¼ 19. Automated Flagger Assistance Devices (AFADs) X Motorist Information Strategies 20. Portable changeable message signs (PCMS) X 21. Dynamic speed message sign X X 22. CB Wizard Alert System X X Traffic/ incident management and enforcement strategies 23. ITS for traffic monitoring/management X X 24. Cooperative/paid police enforcement X 25. Automated enforcement X X 26. Increased penalties for violations X 27. Queue Warning System X X ï¼ 1 High indicates the presence of more than five past studies, medium is between three and five, and low indicates a single study or none at all.
20 4.3. Panel Comments on Initial List From the teamâs suggested list, the Panel unanimously agreed to remove the following strategies. â¢ VSL: FHWA, as part of Accelerated Innovation Deployment grant, awarded $750,000 to Utah Department of Transportation to test, evaluate, and develop guidelines for the use of VSL in work zones. As a result of this new information, the Panel felt the inclusion of VSL for additional field studies is not the best use of the project resources and agreed to remove it from consideration for field evaluation. â¢ Queue Warning Systems and Dynamic Lane Merge Systems: several states were already implementing and evaluating these strategies. â¢ Sequential warning lights are inexpensive and the Panel considered the needs of the project would be better suited by focusing on other strategies. â¢ Temporary rumble strips are used extensively and several states are currently testing them. 4.4. Final List of Treatments for Field Evaluation The Panel then agreed to evaluate the following strategies that are generally applicable to all DOTs, pending (1) acquisition of evaluation sites and (2) new information (evaluations) available that may eliminate any of these from consideration. 1. Truck Lane Restrictions. 2. Ramp Metering. 3. Reversible Lanes.