It’s 7:45 AM on a freeway outside a major city. Inbound traffic slows from 65 mph to a crawl as three lanes of vehicles merge with a busy on-ramp. Within minutes, the backup stretches for miles. Thousands of commuters check their phones, wondering how late they’ll be.
This scene plays out frequently on highways across America. Congestion is frustrating.
But on a few highways—like Virginia’s I-95—something different is happening. As traffic begins to build, digital signs automatically adjust speed limits from 65 to 55 mph and ramp meters control the amount of traffic merging in. Traffic flow smooths out and the bottlenecks are drastically reduced. In some cases, the bottlenecks never form.
This could be the result of a transportation initiative called Active Transportation and Demand Management (ATDM). ATDM is transforming how transportation agencies manage congestion.
What is ATDM?
ATDM represents a fundamental shift in traffic management philosophy. According to the Federal Highway Administration, it’s “the proactive and dynamic management, control, and influence of travel demand, traffic demand, and traffic flow of transportation facilities.”
ATDM is about actively managing traffic in real-time—not reacting after problems occur. Traditional traffic management waits for congestion to happen, then responding by building new roadway infrastructure.
ATDM takes a different approach. It starts with smart infrastructure upgrades that can be deployed quickly—like hardened shoulders, variable message signs, and detection systems. Then it uses real-time data to actively manage these assets, making dynamic adjustments before congestion spirals out of control.
It’s like using air traffic controllers instead of building bigger airports. Air traffic controllers guide planes around weather and traffic moment by moment. ATDM does the same thing for highways.
There are many proven ATDM strategies. Four of the most common approaches include:
- Part-Time Shoulder Use (PTSU): Opening shoulders for traffic during peak hours
- Variable Speed Limits (VSL): Dynamically adjusting speed limits to smooth traffic flow
- Queue Warning Systems: Alerting drivers to slowdowns ahead before the end of a dangerous queue
- Adaptive Ramp Metering: Controlling on-ramp traffic to manage freeway congestion
Each strategy responds to conditions as they change—hour by hour, even minute by minute.
How These Strategies Work
Part-Time Shoulder Use turns existing shoulders into travel lanes during peak demand periods. On Ohio’s I-670 SmartLane, for example, the DOT opens the shoulder during afternoon rush hours, giving drivers an extra lane when it’s needed. The approach is simple and cost-effective. And it works.
Variable Speed Limits change speed limits based on prevailing traffic conditions. This helps prevent the traffic queues that disrupt traffic flow. When sensors detect congestion building, agencies lower speed limits for approaching traffic. This gradual reduction keeps traffic flowing smoothly.
Queue Warning Systems solve a visibility problem by showing a “queue ahead” warning to traffic approaching an end of queue. Drivers can’t see unexpected congestion around curves or over hills until it’s too late. One implementation, PennDOT’s virtual queue protection system, detects where traffic is backing up and warns drivers miles in advance. The result? Fewer rear-end collisions.
Adaptive Ramp Metering works like a valve, letting more cars onto the highway when there’s room and holding them back when it’s crowded—preventing additional congestion caused by excessing merging. For example, California’s I-80 system uses real-time data to adjust metering rates throughout the day.
ATDM Proven Results
The results from ATDM implementations tell a compelling story.
Virginia DOT’s variable speed limit implementation on I-95 near Fredericksburg reduced fatal and serious crashes by 13% in the VSL zones. Travel times became more predictable and there were 22% fewer instances of vehicles traveling 10+ mph over the speed limit.
Ohio’s I-670 SmartLane project delivered similar success. Using part-time shoulder lanes, the DOT increased average travel times from a 10–20-minute trip to a consistent 5-6 minute trip.
PennDOT’s queue warning system has seen impressive safety improvements. Truck-related fatal crashes fell by 41% and the system is estimated to save over $50 million annually through crash reductions. These improvements represent lives saved, injuries prevented, and secondary crashes avoided.
These aren’t pilot projects anymore. They’re proven solutions.
Where Data Fits In
Behind every successful ATDM deployment is a foundation of accurate, timely data. From initial planning to daily operations, agencies rely on traffic intelligence to make these strategies work.
Think of ATDM implementation as a continuous cycle—what transportation professionals call the “project lifecycle.” Data drives decisions at every stage of this lifecycle.
The lifecycle begins with identifying problem areas where agencies analyze years of historical data to find patterns. Where does congestion consistently form? Which merge points see the most crashes? What times of day are worst? This level of analysis reveals which ATDM strategies to deploy and where they’ll have the most impact.
Once a solution is deemed feasible and deployed, real-time operations depend on continuous data streams. INRIX probe data detects changes in traffic conditions across the entire corridor—tracking speed changes by lane, identifying where queues are forming, and pinpointing bottleneck locations. When speeds drop below thresholds or new queues develop, operators see it immediately. This real-time visibility lets them activate variable speed limits, update queue warning messages, or adjust metering rates.
The cycle completes with performance measurement. Using INRIX data, agencies can track the benefits and performance of their implementations—measuring crash reductions, travel time improvements, and throughput gains. When agencies can show reduced congestion, increased travel times or improved safety, the business case for expanding adoption strengthens. Success begets more ATDM implementations.
The Path Forward
Every day, transportation professionals face the same challenge: how to manage growing traffic with limited funding. ATDM offers a practical approach—leveraging existing infrastructure with smart technology to deliver results that once required costly expansions.
In our next post, we’ll dive deeper into specific ATDM use cases. You’ll learn when to deploy each approach, what data you need, and what results to expect based on real-world deployments.
The future of traffic management is proactive, not reactive. And it’s happening now on highways across America.
If you’re interested in finding out how INRIX can help you implement or improve ATDM strategies book a demo to learn more.