Traffic Incident Management
USDOT Congestion Initiative Focus
Traffic Incident Management
You're driving in rush hour traffic, traffic is heavy, but it's still moving. Then, all of a sudden, traffic comes to a stand still. You wonder why. When you finally make it to the "problem" it seems to be nothing more than a flat tire. Often, there will be no apparent reason for the slowness and traffic returns to its normal speed. What happened? Why did such a small event cause such a big problem?
Lane-blocking incidents affect traffic flow far out of proportion to the number of lanes blocked. An incident blocking one lane out of three on a freeway reduces the capacity of that facility by approximately 50 percent. Blocking two lanes of three reduces capacity by nearly 80 percent.
If a lane is blocked when traffic flow is at or near the capacity of a facility the queue of traffic that accumulates behind the incident will not dissipate after the incident is removed until the traffic flow into the queue decreases - in other words until the peak period ends. Thus a standing queue of traffic may exist for several hours, even after the incident is removed, depending on when the incident occurred, how many lanes were blocked, and how long the blockage lasted. In general, each minute of lane blockage creates 4 minutes of congestion after the incident is cleared.
The safety of responders, such as the law enforcement, fire, and emergency medical services personnel shown here, continues to be of utmost importance under Federal and State initiatives on incident clearance.
Not surprisingly, of all the reasons for traffic congestion, traffic incidents cause approximately 25 percent of total delay. For this reason the Federal Highway Administration (FHWA) has in place a robust Traffic Incident Management (TIM) program to assist State and locals transportation agencies in reducing the time it takes to restore capacity following a traffic incident. TIM is a planned and coordinated process to detect, respond to, and remove traffic incidents and restore capacity as safely and quickly as possible. Quick clearance of traffic incidents also reduces the likelihood of secondary incidents such as crashes, or stalls from overheating or running out of gas. Quick and coordinated clearance also increases safety for travelers and incident responders. Promoting more aggressive and widespread traffic incident management is an important strategy to lessen the effects of nonrecurring congestion as well as provide a safer driving environment.
Under the banner of the USDOT Congestion Initiative FHWA signaled out TIM four strategies for particularly intense focus:
- Full-Function Service Patrols
- Driver Removal ("Move It") Laws
- Safe, Quick Clearance Policy Agreements
- Integrated Communications for Transportation and Public Safety Agencies
These strategies complement the recently ratified National Unified Goal (NUG) for Traffic Incident Management. The NUG, developed through the efforts of the National Traffic Incident Management Coalition (NTIMC), is intended to improve safety for incident response personnel and facilitate clearing incidents as quickly as possible. The NTMIC includes 20 national transportation, public safety, and private sector associations working together to improve traffic incident management in the United States.