This study quantified benefits of ITS deployments for work zone applications and also documented key lessons learned from these deployments and previous experience. This study provides practitioners with information on what to expect when deploying similar systems, and also provides key insights into how to design them and tie the design to the objectives for system operation. Agencies interested in deploying similar systems can benefit from the findings of this study. Interested agencies can also use the lessons learned from the deploying agencies to advance their knowledge and to assist with planning, design, and operation of a work zone ITS deployment. This study helps progress current implementation and supplements current research through findings of a quantitative nature for the effects of mobile traffic monitoring and management systems.
The following sections outline the findings across the sites, provide tips and lessons learned from this study, and show how the findings of this study compare with other studies. This chapter concludes with some ideas for future work.
Several sites in this study (NC, TX, DC) focused on diversion and demand reduction, while one (MI) focused on controlling merge conditions. The Arkansas site focused on general work zone condition information, where surveys proved most useful in capturing information on benefits. This study produced several quantitative benefits and provided information and outcomes similar to those anticipated.
Among the two diversion-based sites with quantitative benefits (TX, DC), the results were somewhat different. TXDOT signed the alternate routes and posted messages specifically advising motorists to take one alternate route. A large portion of the trips along the mainline route were likely through trips. DDOT did not sign specific alternate routes, and posted general messages advising motorists to seek an alternate route. A large portion of the trips along the mainline route in Washington, DC were likely commuter trips. It should be noted that based on the data available, it was not possible to determine what portion of the lower mainline volume observed at the DC site was due to diversion versus demand reduction versus congestion. Some of the lower observed mainline volumes in the District of Columbia were likely due to the high percentage of local trips to total trips, since local drivers are more likely to be aware of the work zone and able to divert to another familiar route to avoid the area. The main trip type is important in determining how to design the diversion plans. The findings from the sites with active diversion noticeably expand the body of knowledge regarding work zone ITS, as quantitative information on diversion rates was not abundant prior to this study.
The Michigan site showed quantitative benefits in smoothing traffic at the merge point. The dynamic lane merge site showed results similar to that of previous studies, while expanding on comparisons between time periods with activation and no activation. The Arkansas site provided information on the opinions and reactions of drivers as stated directly in survey responses and showed benefits based on user surveys that indicated the system helped motorists better plan for and make trips.
Overall, the benefits from this quantitative study were positive. The results of the key measures used in this study are summarized in Table 21.
|Location||Type of System Used||System Objectives||Key Performance Measures||Benefits Based on Relative Change in Measures|
|District of Columbia||Real Time Information System||Provide delay and travel speed information and reduce congestion by actively diverting traffic||Traffic Diversion, Queue Lengths||3% to 90% lower observed mainline volumes (with an average of 52%) over 9 observation periods by warning motorists prior to entering the mainline, compared with similar days of the week*|
|Texas||Delay Monitoring System||Provide delay information and reduce demand and congestion by actively diverting traffic||Traffic Diversion||1% to 28% reduction in mainline traffic volume (with an average of 10% reduction) over 20 observation periods where the system actively diverted traffic during congested periods, lessening the demand for restricted mainline capacity|
|Michigan||Dynamic Merge System||Reduce aggressive driving, smooth traffic flow and reduce delay at merge point||Aggressive Maneuvers||Significant reduction in forced and dangerous merges when flashers were on (by a factor of seven for forced merges, and a factor of 3 for dangerous merges), potentially reducing the risk of rear-end and side-swipe collisions near the merge taper|
|Reduce delay from aggressive passing at the merge area||Travel Times||Increase in travel times (from an average of 4 minutes to 7 minutes) when lights were flashing due to slightly longer queues prior to merge|
|Arkansas||Work Zone Information System||Improve traveler safety by providing real-time information to motorists||Survey Response to Safety-Related Questions||82% of surveyed drivers felt that the ITS system improved their ability to react to stopped or slow traffic. 49% of surveyed drivers agreed that they felt safer traveling through the work zone because of the electronic messages, 17% were neutral, 32% disagreed, and 2% did not answer.|
|North Carolina||Delay Monitoring System||Provide delay information and reduce demand and congestion by actively diverting traffic||Traffic Diversion||N/A – system did not fully activate|
The study team observed several common keys to success and lessons learned across agencies when deploying work zone ITS applications.
A critical element to using work zone ITS successfully is for agencies to map out a decision-making process when planning for ITS for work zone traffic management. The process should involve setting goals and objectives for what the owner-agency wants the system to do. Agencies should consult vendors and inquire about specific solutions, but the solution should match the overall goals and objectives for the deployment that are established by the agency. The goals and objectives should be kept current as the deployment progresses, and agencies should monitor how well the system is meeting the intended goals.
Based on this study, several key considerations are identified that should be considered for every ITS deployment:
- The intensity of construction activities and anticipated traffic mobility and safety impacts.
- The level of demand for the area under construction.
- Availability and adequacy of alternate routes, especially when diversion is planned.
- Needed enhancements to ensure that alternate routes operate efficiently during construction (signal timing changes, minor improvement projects prior to mainline construction, etc.).
- Access to and availability of other mode choices during the construction period.
Assessing these considerations during system design and development is important to help ensure that the ITS is needed and can be used effectively, both of which are key to knowing if an ITS deployment in a particular work zone is likely to be a good investment.
In each site studied, a champion was active in selling the concept and ensuring momentum for the deployment continued at an appropriate pace to lead to the successful deployment of the system. Additionally, each site had the appropriate leadership from a group of individuals within the agency to ensure appropriate levels of communication across different groups with the transportation agency and external to the agency with groups such as law enforcement, contractors, and vendors.
The owner-agencies typically hired a vendor who in turn directly provided or procured the services of a local firm to provide hardware, communications, and on-site maintenance and support. However, in some cases, the construction contractor hired the vendor. Irrespective of the arrangement, proper communication channels should remain open between the owner-agency, the construction contractor, the design consultant (if applicable), and the vendor to ensure system success.
In addition to these overall tips and lessons learned, the study team made some observations that apply to specific aspects of system development and deployment, as outlined in the sections below.
- Agencies should develop goals for the system based on systematic consideration of the potential impacts to traffic from the planned construction activities so that the system design is appropriate for the conditions.
- Goals and objectives for the system should be as specific and detailed as possible (e.g., to reduce aggressive maneuvers at the work zone taper) to maximize benefits from appropriate system design.
- The system concept should be designed around the detailed goals and objectives to ensure adequate mitigation of expected impacts.
- Demand levels and capacity restrictions from construction should be studied early on to identify the potential impacts from construction and validate the need for a portable traffic management system.
- If the agency is also implementing other countermeasures to mitigate traffic impacts (such as night work only), the agency needs to consider how much this will lessen the impact/usage of the ITS system and factor that into its decision on whether to deploy ITS for the given work zone.
- The construction contractor should be involved to the greatest extent possible in system deployment to allow for proper timing in deployment, and to ensure that the contractor understands the importance of the system and the placement of the system components. This may help ensure that the system is active within the appropriate time periods and locations during construction.
- The system deployment schedule should be tied to the construction activity schedule to ensure that the system is deployed at the right time to maximize the effectiveness of the investment.
- Adequate time should be allotted for system procurement, installation, and testing so that the deployment covers early construction impact periods.
- Right–of-way use permits may be required prior to equipment installation, may take extra time to complete, and should be accounted for to ensure the deployment covers the early construction impact periods.
- All stakeholders should be involved early in system planning and throughout design to ensure roles and responsibilities are adequately communicated.
- Educating stakeholders who may not be familiar with work zone ITS, such as the media, the public, and law enforcement, is important in ensuring the cooperation needed for system success.
- Agencies should design work zone ITS systems with flexibility in mind since work zones are highly variable environments and system adjustments may be needed during deployment.
- Adequate communication must occur between communications experts (ITS vendors) and traffic and construction engineers (owner-agency) to effectively plan, design, operate, and maintain the system.
- Vendors can assist agencies with determining the best design for a deployment by gaining a solid understanding of the owner-agency's goals for alleviating impacts from the work zone.
- The system design should include proper evaluation of detector spacing and coverage to obtain the accuracy and precision of data needed for the system, particularly if system goals include displaying real-time travel time information.
- Agencies should consider effects on local streets from diverting traffic around the work zone.
Operation and Maintenance
- Agencies can benefit from hiring a software/system vendor that has a local partner company that supplies hardware, message boards, and can be more readily available to perform routine inspection and maintenance of the system.
- Leasing system components from a vendor or local hardware company can save on long-term maintenance and replacement costs.
- Agency personnel should validate system detector data through various means, such as observation of field volumes compared with data archived from the same time period, as a check that the system is functioning as intended.
Prior to starting this study, the study team assumed that work zone ITS systems would be "off-the-shelf," tested, proven solutions. This proved to not be the case in several instances. While the hardware, software, and communications technology may be tested and may operate correctly, these systems must be planned and designed from scratch for each work area to have the maximum effectiveness. Sensor location, message board location, types of information posted, and algorithms for calculating the metrics upon which the system will activate could benefit from standardization or guidance. Vendors have proprietary solutions that likely differ in process. Uniform guidance on planning and designing the systems would likely prove useful for agencies.Previous | Next