How Traffic Data is Reshaping Infrastructure Management
Transportation infrastructure improvements are vital for a healthy system, but the construction phase, or an unexpected closure can bring major disruptions to drivers. Today, sophisticated traffic data, like that from the National Transportation & Analytics Solution (NTDAS), is empowering transportation agencies to manage these disruptions more effectively, minimizing congestion, reducing costs, and better informing the public.
Pinpointing the Impact on the Network
The key to managing road closures is understanding how drivers react and what alternate routes they choose. The data from NTDAS, which provides average speeds for vehicles at intervals as short as 5 to 15 minutes, is highly sensitive to changes in congestion and is a direct reflection of vehicle flow and reliability.
- Understanding Congestion: Under congested conditions, speed decreases sharply as traffic enters stop-and-go patterns, allowing analysts to measure changes along and near a transit corridor. The Speed Trend Map tool offers a visual way to see how speeds change in and around a construction project, like the example shown for the California Route 210 expansion.
- Identifying Detour Impacts: Traffic diversions can impact local roads or adjacent major routes as drivers seek new paths around a closure. For instance, a long-term bridge closure on I-276 showed an immediate impact, with increased congestion on nearby bridges like I-295, a change that can be visualized using the Congestion Percent Trend Map tool. Similarly, the short-term closure of the Richmond Bridge led to considerably lower westbound speeds on one alternative route, CA 37.
Enhancing Models with Data Fusion
To gain the deepest insights, NTDAS data is often combined with other sources:
- Volume Counts and Detour Information: Combining the speed data from NTDAS with external data like construction plans, schedules, and volume counts, or bridge count data from tolls and sensors, helps determine where drivers are going and enhances traffic models.
- Environmental and Safety Analysis: The use of speed and travel time data can be foundational for analyzing environmental impacts, such as emissions related to stop-and-go traffic. The data can also be used for advanced safety analyses by providing a clearer picture of traffic performance under stress.
By leveraging tools like the Trend Map and Performance Charts within the National Transportation Data & Analytics Solution (NTDAS), transportation professionals can shift from reactive to proactive traffic management, ensuring that necessary infrastructure work causes the least possible disruption to communities.
Traffic Data Applications: Long-Term vs. Short-Term Closures At-A-Glance
Analyzing traffic patterns before, during, and after disruptions allows transportation agencies to evaluate impacts and implement effective mitigation strategies.
Long-Term Disruption: Roadway Expansion
For a planned, long-term project like a roadway expansion, the focus is on managing the system degradation during construction until the project is complete, and then assessing if the finished system performs as predicted.
Long-Term Disruption: Unplanned Bridge Closure
When an unforeseen, long-term event like an emergency bridge closure occurs, the immediate concern is minimizing the volume impacts on adjacent bridges and quickly putting mitigation measures in place.
Short-Term Disruption: Emergency Bridge Closure
A short-term, critical network disruption, such as a one-day bridge closure, is often evaluated to quantify the overall economic impact and assess network resiliency.
The Conclusion: Optimizing Closures for Minimal Disruption
By analyzing historical traffic data, agencies can make informed, data-driven decisions that reduce the burden on commuters and the environment.
- Finding the Best Time to Close: The ability to look at historic speed and congestion data across different time intervals (5-minute, 15-minute, 1-hour) and over long periods allows agencies to identify the least disruptive times for planned closures. For example, by looking at the daily and weekly patterns, they can identify the off-peak times or seasonal variations where traffic volumes are naturally lower, minimizing the number of drivers affected.
- Quantifying the Cost of Delay: The User Delay Cost Analysis tool is crucial for evaluating the economic impact of a disruption. In the case of the Richmond Bridge closure, the difference in estimated user delay costs was approximately $600,000 higher on the day the bridge was closed, representing a 30% increase compared to a typical day. Quantifying this cost helps justify infrastructure investments and evaluate network resiliency for future incidents.
- Informing Management Strategies: Detailed traffic flow data supports better management of operational controls. This includes improving dynamic message signs to provide real-time guidance, adjusting local roadway signal timing to handle increased detour traffic, and directing police enforcement efforts where congestion is highest.
