TRAFFIC CONTROL CONCEPTS FOR INCIDENT CLEARANCE
6.0 MONITORING AND ADJUSTING TRAFFIC CONTROL
On-scene traffic control needs can change dynamically as the response efforts progress. The first priority upon arrival is to establish initial traffic control to provide a safe work area for responders and minimize chances of secondary crashes. As resources with traffic control devices/equipment arrive, the traffic control can be adjusted to a more “standard” format. Traffic management hierarchy at an incident scene includes: 31
- Establishing initial traffic control,
- Managing roadway space by opening and closing lanes,
- Blocking the area of the scene needed for victim and responder safety,
- Parking vehicles to minimize impacts,
- Deploying personnel to assist,
- Using intelligent transportation systems (ITS) field devices as support, and
- Using detour routes when necessary.
Traffic control device placement is impacted by the expected duration of the incident. Upon arrival, responders should make an estimate of the magnitude of the incident and then estimate an expected duration for recovery; traffic control can then be set up based on this estimate. Expected durations of an incident are defined as follows: 2
- Minor – Under 30 minutes
- Intermediate – From 30 minutes to 2 hours
- Major – Over 2 hours
Responders without the understanding of basic traffic control concepts may prefer to block all lanes, which may unintentionally increase the chances of secondary crashes. A preferred sequence would be to go from full roadway closure to directional lane closure to multiple lanes to single lane and to shoulder closure until the incident is fully resolved and traffic flow returns to normal.
The roadway lane closure must be managed so that only the lanes absolutely necessary for protection of the responders and victims are closed. Every effort should be made to minimize the times these lanes are closed. The number of closed lanes may change several times during clearance efforts, so traffic control needs to be established and then monitored/changed to fit changing conditions.
Traffic control devices need to be adjusted, as warranted and as conditions change, by personnel familiar with their use. Incident responders responsible for traffic management need to stay informed about recovery operations, and they need to continually assess incident impacts on traffic flows and monitor the traffic queues. Incident responders need to pass this information on to traffic management center staff, charged with passing this information on to motorists. On-scene traffic control needs can change dynamically as the response efforts progress. As resources with traffic control devices/equipment arrive, the traffic control can be adjusted to a more “temporary work zone” format.
Alternate routes can be used when necessary. For example, they may be used with full roadway closure, in either or both directions, especially when long duration closures are expected, such as when there is roadway or structural damage. Agencies that implement detour/alternate routes need to be engaged in the planning process and be knowledgeable of the implementation procedures. Traffic control may also be needed on these detour/alternate routes because of abnormal traffic conditions as vehicles divert around an incident in search of a less congested way to travel.