Blocking Techniques for Roadway Incidents

April 21, 2016
Jack Sullivan illustrates blocking and parking tactics for roadway incidents to protect responders and increase scene safety.

The highway is still one of the most dangerous work areas for firefighters and emergency medical personnel to work. Vehicle fires, motor vehicle crashes, medical assist calls, hazardous materials incidents, brush fires and structure fires can all put emergency personnel at risk of being struck by a vehicle while operating along or near roadways. In 2015, there were nine incidents involving firefighters and/or EMTs who were struck and killed by vehicles. There were many more struck-by-vehicle incidents that resulted in injuries—some very serious-to emergency personnel and/or caused emergency vehicle damage.

Motorists today are more distracted than ever before. Smartphones with all their capabilities are a major contributing cause, but we also have plenty of drivers who are driving while impaired by drugs or alcohol, or lack of sleep. We also have more disgruntled drivers on the road than ever before who completely disregard any authority figures on scene and just do what they want to do, which can put emergency personnel at risk of being struck. Your uniform, personal protective gear, badge or emergency vehicles on scene do not cause people to adjust their driving speed in many cases. Even if they can see you, it does not guarantee that they will slow down and proceed with caution. As a result, it becomes necessary for firefighters and EMTs to take defensive actions as they arrive at incident scenes including using their emergency vehicles for a block to protect responders and the victims they were responding to assist in the first place.


Depending on which document you look at, the term “blocking” might also be described as the “safe parking” or “safe positioning” of emergency vehicles at roadway incidents. In the fire service, the term most often used is “block” or “blocking.” A block is when an emergency vehicle is used to protect an incident work area by parking across a lane or lanes of traffic. The unit should be stopped upstream of the incident area and parked at an angle across a lane or two of the roadway. In many cases, the shoulder of the road will be considered a lane if that is where the original incident is located. Parking at an angle makes it easier for approaching traffic to identify that your unit is stopped, parked and not moving. Units parked in line with traffic, even on the shoulder, are not as easy to identify as stopped and approaching traffic will often not recognize that the unit is parked instead of moving with traffic.    

As an example, a vehicle parked on the left shoulder of the road is on fire. The fire department responds and when the first fire unit arrives on scene, they should park at an angle and block the left shoulder and next adjacent lane of traffic. We refer to this as “Lane +1” blocking. In another example, two cars have a minor crash and pull off onto the right-side shoulder. One passenger complains about neck pain and an ambulance is requested. When responding units arrive on scene, one of the emergency vehicles should block the right shoulder and next adjacent lane of traffic. The Lane +1 block (see Illustration 1) in this case will be the right shoulder and right travel lane. 


There are two ways to park at incident scenes. Most common for fire and EMS services is the “block positioning” as described above. The other way is what we refer to as “linear positioning” or a linear block. Linear positioning places the emergency vehicle upstream of the incident in the same direction of travel in the same lane or shoulder area as the original incident vehicle(s). Linear positioning is most often used in situations like disabled vehicles or traffic stops by law enforcement. As a fire or EMS scene starts to terminate or de-escalate it may be appropriate to move response vehicles remaining on scene to a more linear position to open up some lanes of traffic to reduce the backlog (see Illustration 2).     

Since in most cases in the fire service we will use multi-lane block positioning, let’s look a little more closely at some of the details of setting a proper block. There are a few more things to think about besides just parking at an angle upstream of the incident. For example, you have the choice to block right (angle the front of the blocking unit toward the right) or block left (where the front of the unit is angled to the left). Which way you choose to block is influenced by several things: location and type of incident, traffic pattern and equipment you expect to use off the unit (see Illustration 3).

Common roadway incidents

Incident 1—A car fire on the right shoulder of a two-lane interstate highway (see Illustration 4). As you approach the scene you can see fire showing from under the hood area. You will be pulling a line to extinguish the fire. With these facts in mind, you decide to block right and angle the engine to the right in both the right lane and right shoulder (Lane+1 block). By choosing to block right, you offer the pump operator some protection from oncoming traffic while operating at the scene. It would be best if another unit assisting at the scene parks in a block left position, upstream of the first engine, to indicate to traffic that they should move to the center and left lanes as they pass the incident. 

Incident #2—A two-car rear-end collision in the left lane of a multi-lane interstate highway (see Illustration 5). As your unit approaches the scene you observe two vehicles stopped in the left lane with people walking around outside the vehicles. You decide to block right, upstream of the cars and block the left shoulder and left lane. Your first objective will be to get the people on scene away from passing traffic and into a protected area. If there are no injuries, consider moving the vehicles into the left shoulder if local laws and procedures allow it.

Incident #3—A medical assist for possible asthma attack in the vehicle on the right shoulder of the same multi-lane interstate highway (see Illustration 6). Upon approach to the scene you note one car parked on the right shoulder with people standing next to the passenger side of the car waving you in. In this case, you might choose to block left and initially block the right shoulder and right lane. The block right angle upstream sends a message to approaching traffic that your unit is stopped, parked and not moving. The left angle appearance encourages traffic to move left as they approach the scene. 

Incident #4—A two-car rear-end collision in the center lane of the three-lane interstate highway in heavy traffic (see Illustration 7). Upon approach, you observe there is already a significant backlog forming and drivers are dodging between lanes trying to get past the incident. It appears that there is one person still in the passenger seat of the lead vehicle being tended to by others. Expecting an injured patient, you decide to block left and take the right lane and center lane forcing traffic to move toward the far left lane to pass. You want to prevent traffic from passing the incident on both sides in this type of situation. Request another unit to block the right shoulder and right lane upstream of your unit as soon as possible because there will always be that smart driver out there who sees an opening on the right shoulder and decides to blow through it as quickly as possible. Deploy cones and/or flares on the right shoulder before the other unit arrives to prevent that stray motorist from passing on the right. 

After you stop your vehicle

Once you choose your blocking position, there are a couple of other things that need to be done and considered as you park. The driver/operator should turn the front wheels of the unit away from the incident work area in case the unit is struck from behind (see Illustration 8). All firefighters should stay seated and belted until it appears traffic is either stopping or moving around the unit. Watch for approaching traffic before exiting the unit and try to dismount on the side of the unit away from passing traffic wherever possible. The driver/operator should also deploy chock blocks on the unit per local procedures. 

All firefighters on scene should be aware of, and avoid, the danger zone known as the “zero buffer” now that your unit is parked in a blocking position. The zero buffer is anywhere your unit is closest to moving traffic—usually the front bumper or rear step area of the unit (see Illustration 9). We want to make sure all personnel recognize the zero-buffer area and proceed with caution before moving through that area. It would be preferable for personnel to avoid the zero buffer all together by going around the unit the other way if possible to grab equipment from a compartment. If it is not possible to go around, then personnel should stop before entering the zero buffer and look for oncoming traffic before proceeding around the corner. Do not assume that approaching traffic will see you or stop when you come around the zero-buffer area. 

The next thing to consider is what we can do to warn oncoming traffic about our unit parked at the incident scene. First you should be requesting the assistance of law enforcement and/or local transportation or public works units for traffic-control assistance upon arrival on scene and as part of your size-up report. If you are fortunate enough to have safety service patrols operating in your area, be sure to request them to the scene as soon as possible (see Illustration 10). Advise what traffic control assistance you need in specific closed lanes on the highway. Advise dispatch that you are blocking specific lanes as part of your size-up. If you need additional lanes blocked, be sure to specify where you want incoming units to position upon arrival. All efforts should be made to keep all emergency vehicles on one side of the road or the other whenever possible. By advising units where you want them to position before they can see the scene, you will help them position appropriately on approach. 

If possible consider also deploying cones and/or flares behind your unit to get the attention of approaching motorists. If your fire unit is the only emergency vehicle on scene, you are responsible for temporary traffic control until you get law enforcement or another unit on scene to assume that responsibility. In some cases the block positioning may be the best you can do in the first few moments upon arrival at the scene. If you have the personnel available, cones and flares deployed upstream of the unit can help prevent a motorist from running into your emergency vehicle. We have seen a significant increase in the number of emergency vehicles being hit while blocking at emergency scenes. It might be hard to believe that motorists can’t see a large fire vehicle with lots of flashing lights parked in the roadway, but the reality is that some drivers aren’t even looking out of their windshields. In many documented cases the striking drivers are drowsy, drunk, or distracted by something in their vehicle or all of the activity at the incident scene. Cones upstream of the incident can cause drivers to recover before they actually hit the emergency vehicle. 

Blocking with large emergency vehicles is an important and critical aspect of protecting a roadway incident scene. In the early stages of an incident, it is many times the responsibility of the fire department to provide that initial block to protect the victims of the original incident, the emergency personnel on scene and other motorists in the area. Be sure your personnel know the proper way to establish a block and coordinate your policies and procedures with other responding agencies so all personnel are working from the same guidelines. 

We have provided a video that illustrates and reinforces the information in this article at:

JACK SULLIVAN is the Director of Training for the Emergency Responder Safety Institute, a committee of the Cumberland Valley Volunteer Firemen’s Association. Sullivan retired from active service after 25 years as a firefighter, company officer and safety officer. He is also a Certified Safety Professional with 35 years of safety consulting and training experience. He works with several national committees on the subject of highway incident safety and teaches classes and workshops nationwide for emergency services personnel. Sullivan is also a master instructor for the Federal Highway Administration SHRP 2 Traffic Incident Management Train-the-Trainer program.

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