A rolling road block (also known as a “Slow Roll” or a “Rolling Slowdown”) is a means of slowing and controlling traffic to clear a section of roadway and allow a work operation which requires short duration access to an entire roadway (typically a freeway or other controlled access highway).
A rolling roadblock typically involves:
- A shadow vehicle in each lane
- A shoulder of 8 foot or greater width, possibly assisted by police
- Slowing and pacing upstream traffic at the reduced speed to create a downstream gap in traffic of sufficient duration to accomplish the work in the roadway.
Typically used when:
- Cable, overhead sign structure, bridge beam, traffic counter tubes, pavement monitoring devices; etc.) is being strung/placed across the highway or to change a traffic pattern in a temporary traffic control zone.
- A simpler variation has also been used for post-storm clean-up on elevated segments of freeways with close echelon plowing to pull built-up snow from median barriers to the right side of roadway.
Prior to implementing a Rolling Roadblock
- The Regional Traffic Engineer should be contacted before selecting a rolling roadblock for traffic control in case there may be other preferable traffic management alternatives such as detours and/or other planned events which could further impact traffic operations.
- The Regional Traffic Command Center (TMC) and the appropriate State Police troop and local police agencies must be notified at least 24 hours prior to the closure.
- The region should also consider requiring advance deployment of Portable Variable Message Signs (PVMS) warning of the event several days prior to the event to allow motorists to plan adjustments to their route or time of travel.
Planning the Rolling Roadblock
When determining where/when to start the rolling roadblock, consider the following:
- Duration of work
- Clearance time for last uncontrolled vehicle to pass by work area
- Projected travel time of rolling roadblock - 15 mph= 1 mile in 4 minutes
- Number and location of entrance ramps requiring closures
- Start in a tangent section with adequate sight distance
- Periods of lightest traffic to minimize impacts
- Communication and preparation meeting
Work duration should be kept to a minimum, no more than 15 minutes.
The permittee/contractor should be required to demonstrate that they will deploy the resources necessary to complete the work within the specified time period.
The selection of the speed of the roadblock should consider the work duration and the location of upstream on-ramps which need to be closed but should generally be 15 mph or greater. 15-minute duration would require closure of at least 5 miles of mainline roadway at a 20-mph pace and 3.75 miles at a 15-mph pace plus buffer space, set-up and deceleration distance.
Any on-ramps within the required distance must be closed and traffic either detoured or adequate storage for queued traffic provided on the ramp.
The work requiring the rolling roadblock shall be scheduled during periods of light traffic in order to minimize impacts, typically early Saturday or Sunday mornings (between 6:00 and 8:00 AM) in daylight conditions.
The work shall also be scheduled to avoid inclement weather, adverse environmental or roadway conditions which could ultimately affect visibility, vehicle handling, or the time needed to accomplish the work within the highway.
A preconstruction/preparation meeting with all parties involved is required prior implementing the rolling roadblock. All logistics including communication issues and scheduling issues shall be resolved during this meeting. Also, contingency plans for concerns which could stop the roadblock or delay the operation shall be made. Cell phones or walkie-talkies, if radios are not workable, shall be used to communicate during the rolling roadblock implementation.
For permit work, the permittee or its contractor should provide or ensure a common communication system to all parties.
On contract work, the contractor should provide a common communication system to all parties. The common communication system shall include, workers, clearance vehicle, all rolling roadblock drivers, traffic controllers at on-ramps and, if participating, police. Work should not begin until the Department’s representative on-site is confident that the work can be completed within the specified time and the communication system is adequate to accommodate all reasonably foreseeable scenarios.
Police participation is optional and at the discretion of the Regional Office and the State Police troop or other local police agency. In general, police participation should be unnecessary unless there are site specific enforcement concerns.
- A police car should never be used to close an open lane of traffic.
- A police car may be positioned in front (downstream) of a TMA equipped shadow vehicle and/or on a closed on-ramp. Flashing lights should be placed immediately downstream of the shadow vehicles forming the rolling roadblock to discourage drivers from passing the roadblock.
- Position the police car where it is visible to traffic through the lateral gap between the shadow vehicles to enhance the visibility of the police car. However, gaps between the shadow vehicles should not be wide enough to encourage vehicles to pass between them.
- A police car may also be positioned, with lights flashing, on an on-ramp which will be closed to discourage ramp traffic from passing the flagger. If there are multiple on-ramps within the roadblock limits, deploying the police car at the downstream ramp may better enable it to stop a vehicle which has breached the gap between the work area and the roadblock.
The drawings show the closure of a two-lane roadway; however, three and four lane roadways can be closed by either adding additional shadow vehicles or by closing lanes using a typical lane closure set-up, which will reduce the number of shadow vehicles needed. At some sites, it may be preferable to use typical lane closures to reduce the traffic flow to one lane before deploying the rolling roadblock.
- All traffic control devices used to warn or to guide traffic shall comply with the National Manual on Uniform Traffic Control Devices (MUTCD).
- Advance warning signs or portable VMS (SLOW TRAFFIC AHEAD/BE PREPARED TO STOP) should be on the right side of the roadway one mile upstream of initial position of roadblock vehicles. Permanent VMS controlled by the TMC can also be used, if appropriate.
- An additional portable VMS either on a trailer hitched to a truck or mounted on the truck should be located on the right shoulder 1500 feet upstream of the initial roadblock location and should move as necessary to remain approximately 1500 feet upstream of the queue.
- A police car (if available) on the shoulder near the upstream end of the queue can enhance queue warning.
- Advance warning signs or VMS on both sides of the road is desirable. If there is not enough room on the shoulder, a lane closure to accommodate the VMS may be appropriate, especially for three-lane, or wider, roadways. If a VMS is used on the left side of the roadway, it should be placed ½ mile upstream of the initial roadblock position and not directly across the roadway from the first VMS. Offsetting the VMS boards from each other will avoid confusion which can result from two VMS boards directly across the roadway from each other displaying different portions of their message at any given instant.
- All required VMS and advance warning signs shall be in place prior to implementing the rolling roadblock.
- Advance warning signs shall be placed on affected on-ramps and the crossroad to warn approaching vehicles of stopped traffic on the ramp or of a ramp closure. The signing will depend on site specific conditions including the expected length of queued traffic and the length of the ramp. If the queued traffic on the ramp will affect traffic operations on the crossroad, signing will be needed on the crossroad. A W20-7 flagger sign and a W3-4 BE PREPARED TO STOP sign would be the minimum advance warning needed on the ramp.
The rolling roadblock should be staged from the right shoulder if no on-ramp or rest area is available. The upstream shadow vehicle should close the shoulder (if shoulder is 8 ft. or wider) or the right lane (if the shoulder is less than eight feet wide). The second downstream shadow vehicle should then close the next lane to the left and so on.
Step 1: The rolling roadblock shall form near the designated starting point and any on-ramps shall be closed simultaneously or very shortly after, depending on how far downstream the on-ramp is (see Step 2).
Step 2: On-ramp traffic shall be stopped and held by a properly trained traffic controller (flagger).
Step 3: A clearance vehicle initially positioned immediately downstream of the rolling road block shall follow the last vehicle traveling in advance of rolling road block to ensure that there are no moving or parked cars and no open on-ramps or other access points, and to notify the work crew that road is closed and free of traffic.
Step 4: Work in the roadway begins. The clearance vehicle should stop and hold its position immediately upstream of the work site until the work is done to provide a visual cue to the approaching roadblock whether the work is done, and the roadway cleared.
The roadblock shall proceed downstream at the pre-determined speed and be in constant communication with the work site. The speed of the roadblock can then be adjusted to accommodate the pace of the work. A truck either with a mounted VMS or towing a trailer mounted VMS positioned on the right shoulder should maintain an approximately 1500-foot following distance behind (upstream of) the end of the queue. As the roadblock passes an on-ramp, ramp traffic can be released when the mainline queue dissipates or moves downstream, and mainline traffic flow can safely accommodate the merge from the on-ramp. The procedure and timing of the release of vehicles held on the ramps should be determined at the preconstruction/preparation meeting.
Step 5: Once the need for closure has ended, the work crew shall notify the rolling roadblock and the clearance vehicle should pass the site. The blocking vehicles should gain speed and pull over to right side of roadway starting from the left lane. Police, if used, should continue with flow of traffic to ensure controlled acceleration of released vehicles. Inactivate or modify PVMS as appropriate.