The precision immobilization technique (PIT) has been in law enforcement use since the 1980s. PIT is unquestionably an effective tool for ending vehicle pursuits, but not without controversy. A well-executed PIT deployment usually results in the pursued vehicle spinning out to a stop, followed by the arrest of a dazed driver.
There have also been some episodes where the pursued vehicle overturns or strikes an unyielding object, and the driver and passengers of the pursued vehicle or the occupants of an otherwise uninvolved vehicle are injured or killed. News media reporting of these adverse outcomes has caused the PIT and the agencies that employ it to come under scrutiny.
Steps to perform the precision immobilization technique
The PIT requires skill to execute effectively, but it’s not especially difficult to describe:
- The officer intending to use the PIT pulls up behind the target vehicle, offset to the vehicle’s left or right, and overlaps the target vehicle length by two or three feet.
- The officer matches the speed of the target vehicle, then hits the rear quarter panel of the target, just behind the rear wheel, with the patrol vehicle’s right or left front bumper.
- On making contact, the officer turns the patrol vehicle steering wheel one-quarter turn toward the target, then immediately turns the wheel back to the direction of travel.
This impact causes the target vehicle’s tires to break traction and the rear to spin away from the officer’s vehicle. Ideally, the target vehicle should come to rest pointing 180 degrees from the original direction of travel. The officer can then position their patrol vehicle to either provide cover or to hold the driver’s door closed, cutting off the driver’s easiest avenue of escape.
Occasionally, the driver of the target vehicle recovers from the spin and simply drives away, forcing the pursuing officers to try another PIT or resort to some alternative method of stopping the pursued vehicle. In this pursuit video, the California Highway Patrol needed several PIT attempts before the driver was stopped and apprehended:
The final PIT resulted in the target vehicle rolling over multiple times, although the driver suffered no serious injury. Though the steps of performing the PIT are easy to describe it is important for officers to know more about the history of the PIT, other names for PIT and the underlying physics that are involved in a successful PIT.
History of the precision immobilization technique
An article published by the Federal Law Enforcement Training Center (FLETC) credits BSR, Inc. in Summit Point, West Virginia with the development of the PIT in the 1980s. Its true origin may be further back.
A common, but outlawed, tactic in stock car racing is the “bump and run.” One car strikes the one in front of it, connecting at the rear bumper. This causes the target vehicle to lose traction with the pavement and often swerve to the side of the track, leaving room for the rearmost car to pass. The “bump and run” was particularly dangerous because the stock cars were typically moving at very high speeds, making a loss of control or roll over a real possibility.
Other names for PIT
Although the PIT, or precision immobilization technique, is used throughout this article, the method is known by other names, including:
- Pursuit immobilization technique
- Pursuit intervention technique
- Parallel immobilization technique
- Precision intervention tactic
- Tactical car intervention
- Tactical ramming
- Tactical vehicle intervention
- Legal intervention
Physics of PIT
The physics of the PIT are a practical exercise in the conservation of energy. The physicist Émilie du Châtelet postulated in the 18th century that the energy in an isolated system can be neither created nor destroyed; it can only be changed from one type of energy to another. With moving vehicles equipped with internal combustion engines, chemical energy is stored in the fuel tank. As the car is driven, the chemical energy is converted to kinetic energy that propels the vehicle, with a substantial amount of waste heat energy coming off the engine. Most internal combustion engines average only around 20% thermal efficiency.
When the car is slowed or stopped conventionally with the brakes, the kinetic energy is transformed into heat coming off the brake pads or rotors. When police PIT a target car, its tires momentarily lose traction with the road, and the rear end is forced to the side in the direction it was bumped, causing the vehicle to yaw left or right. The kinetic energy still present in the vehicle system continues to force the car in the general direction it was going before it was struck, but the wheels may now be sideways to the force vector. If there isn’t too much kinetic energy to bleed off, the car will skid, usually spinning around as it does so. If there is an excess of kinetic energy because of the velocity of the vehicle before the PIT, the car can roll over, become airborne, or suffer some other undesirable fate.
Another physical law to keep in mind is Newton’s Third Law of Motion, which is that when one body exerts a force on a second body, the second body simultaneously exerts a force equal in magnitude and opposite in direction on the first body. This is possibly easier to envision by playing with a desk toy called Newton’s Cradle, a small frame usually made with five metal balls suspended by thread or fishing line. Bounce the ball on one end against the others, and just the ball on the other end will swing out. Use two balls, and two on the other end react. (Image/DemonDeLuxe via Wikimedia Commons)
Now, instead of little steel balls, imagine that the bodies coming into contact are your patrol car and a heavy-duty pickup truck. You might be expecting the pickup truck to get knocked off course when you PIT it, but it’s more likely your car is going to be the one going sideways. The pickup has considerably more mass than your car, and the force equation is not going to balance in your favor. Pick your PIT targets carefully.
Although it seems like the only PIT maneuvers we hear about are the ones that go wrong, the PIT is actually a useful and usually safe method for ending pursuits. Do a little internet searching, and you can find lots of them that had a force equation in favor of the patrol vehicle. Here’s a video of some successful PITs:
PIT training
PIT is not an especially difficult or complex technique, but it does require training. The training course is typically one or two days, with refreshers every one or two years. One obstacle to training is the wear and tear on patrol cars. A car used in a PIT exercise, either as the target or the police vehicle, will sustain body damage. Some agencies maintain a few cars specifically for PIT training. Reinforced metal bumpers may be in place all the way around the car to protect the body from the worst of the damage.
The training can be done on any open, paved roadway or other surfaces. Some agencies use aircraft landing strips, industrial parks on days where there is little traffic or streets in residential subdivisions where homes have not yet been built.
PIT instructors emphasize that the technique requires finesse. Done right, the driver of the target vehicle barely feels the PIT contact. Instead, the target vehicle driver simply finds themselves spinning out of control, coming to rest facing the wrong direction and looking at police officers ready to make an arrest. Some instructors want to see between six and a dozen successful PITs before they will sign off on a student officer’s competence with the technique.
Alternatives to PIT
Pursuit termination measures used by police fall into two main categories: active and passive. Active measures partially or completely disable the vehicle so that it is more difficult or impossible to drive. The most common active measure in use is tire spikes. An officer, positioned on the side of the road, throws the tire spike carrier, typically an expanding frame or a collapsible tube, into the path of the vehicle being pursued. The tire spikes themselves are hollow pointed quills that puncture and deflate the tires slowly, so there is not a sudden and catastrophic blowout.
The use of tire spikes is not risk-free. The officer deploying the spikes has to be very close to the path of the target vehicle, and the driver of the target is looking for the spikes and will try to avoid them. Each year, multiple officers are injured or killed while trying to deploy spikes when they are run over by the target vehicle.
Tire spikes are also not 100% effective. Desperate drivers continue to flee even after the tires have been ripped from the wheels, running on the rims which may set the vehicle on fire. The target vehicle is often destroyed in the process.
Another anti-pursuit device category is a net or mat made of high-tensile fabric that wraps around the target vehicle’s wheels and immobilizes them. One product requires laying the mat on the roadway so that the target will run over the mat. Another uses a mechanical arm mounted on a police vehicle to thrust the net under the target’s chassis while the vehicles are in motion. The nets are very effective in stopping the target vehicles safely, but they still require getting very close to the target, and the cost of the net, a single-use item, can be prohibitive for some cash-strapped agencies.
Another passive anti-pursuit device is StarChase. StarChase-equipped patrol cars have a launcher mounted on the front grille or bumper. There is also a shoulder-fired version. The launchers shoot a projectile about the size of a softball at the target. The projectile is coated with a heavy-duty adhesive, so it sticks to the target vehicle’s body. When fired, a GPS transmitter inside the projectile begins to transmit the target’s location in real-time. The police can then back off and wait for the target to stop moving before approaching. The StarChase system allows for damage-free recovery of the target, but often without the driver, who may abandon the car.
All these devices are effective in their own way, but few law enforcement agencies can afford to equip all of their patrol vehicles with tire spikes, StarChase or high-tensile mats. Deployment often requires getting dangerously close to the target vehicle, placing the life of the officer in jeopardy from collision or assault.
Advantages of PIT
Absent one of the PIT alternatives, the police agency that chooses to pursue a fleeing vehicle can pursue the driver until they get tired or run out of gas, or attempt a more decisive tactic like the PIT.
Advantages of using the PIT include:
- Immediate termination of the pursuit
- Minimal damage, when done properly, to target and police vehicles
- Police determine where and when pursuit will end
- No extra equipment required
- Minimal training requirement
- Target vehicle occupants are on scene at the termination of pursuit and can be arrested
Disadvantages of PIT
Potential drawbacks to the PIT are:
- Possibility of catastrophic collision, especially when high speeds are involved
- Possibility of heavy damage and/or complete loss of target and patrol vehicles
- Training must be updated periodically
Possible conditions for PIT use
The Fairfax County (Virginia) Police Department was the first to use the PIT in the field. The PIT has since come into widespread use nationally, although some law enforcement agencies prohibit its use, and others set down restrictive conditions where the PIT may be used. These conditions for use or limiting factors include some or all of the following:
- Reason for the pursuit (simple traffic violation, intoxicated driver, stolen car, felony crime, etc.).
- Target vehicle speed at the time the PIT is attempted.
- Roadway environment: interstate highway, local street, presence of other vehicles or pedestrians, physical obstructions, adverse weather conditions, etc.
- Known occupants of the target vehicle: driver only, adult or children passengers.
- Whether the patrol vehicle driver has been trained in the technique, and how recently.
If there is a single critical factor for using the PIT to achieve the desired outcome, it’s probably speed. While some agencies, state police and highway patrols in particular, do not incorporate the speed of the cars at the time the PIT is attempted into their policies, others forbid officers from attempting a PIT at a speed above 40 miles per hour. The reasoning behind this is clear after viewing a few dash cam videos of PITs gone wrong. One of the more graphic examples is this pursuit by the Arkansas State Police, where a trooper executed a PIT at 109 miles per hour:
In this case, not only was the target vehicle destroyed, but the trooper’s vehicle vaulted up and over the target vehicle, getting enough altitude to clip some streetlights. The driver of the fleeing vehicle was killed; the trooper suffered “non-life-threatening injuries.”
Legal concerns
Police are clearly empowered to pursue fleeing vehicles to apprehend the driver or occupants for crimes directly connected with the pursuit or unrelated. In 2007, the Supreme Court of the United States decided in Scott v. Harris (550 U.S. 372) a police officer’s attempts to terminate a high-speed car pursuit do not violate the search and seizure provisions of the Fourth Amendment, even if the pursuit places the occupants of the speeding vehicle at risk of death or injury.
In March 2001, a deputy sheriff in Georgia attempted a traffic stop on a car traveling 73 miles per hour in a 55 MPH zone. Deputy Timothy Scott assisted in the pursuit, momentarily boxing in the suspect vehicle in the parking lot of a shopping center. The driver, Victor Harris, was able to drive away after striking Deputy Scott’s patrol car. The pursuit resumed, covering almost ten miles of road. Deputy Scott requested and was given permission from his supervisor to use the PIT to end the pursuit. However, Scott decided on a different approach and struck the rear of Harris’ vehicle with his patrol car’s push bumper.
Harris lost control of his car, which left the roadway, continued over an embankment, and rolled. Harris was rendered a quadriplegic as a result of his injuries. Harris filed a lawsuit against Deputy Scott and the sheriff’s office that employed him, complaining that Harris’ pursuit and push bar tactic amounted to excessive force and was an unreasonable seizure under the Fourth Amendment.
The court ruled against Harris with unusual unity of opinion, as the late Associate Justice John Paul Stevens was the lone dissenter. The court specifically addressed the hazard to uninvolved innocent persons created by a fleeing motorist as justification to use the potentially deadly force of a police pursuit.
Effects of electronic stability control
One last issue to address is the effect that electronic stability control (ESC) systems have on vehicles impacted during a PIT maneuver. ESC is a computer-managed system that activates when it senses that the vehicle’s tires have broken traction and are skidding. Most commonly, it activates when a vehicle is accelerating on a wet or icy road, and the car begins to fishtail. The effect can be startling. It’s as if the hand of God reached down and grabbed your car before it ran off the road. The skid or fishtail stops immediately, and control of the car is returned to the driver. ESC systems are increasingly becoming standard on new motor vehicles, even the more “no-frills” base models, as it makes cars considerably safer to drive.
ESC is designed to prevent exactly the same loss of control a law enforcement officer is trying to induce in a PIT maneuver. The issue has not gone unnoticed by the automotive engineering community. A highly technical article, Vehicle Dynamics in Response to the Maneuver of Precision Immobilization Technique, analyzes how ESC systems impact the effectiveness of the PIT. Their conclusion is that an ESC system will moderate the effectiveness of a PIT attempt, but not overcome it altogether.
Mercifully, four law enforcement officers in Oregon published a considerably less technical article on the same topic, Effects of Electronic Stability Control on the Pursuit Intervention Technique. The FLETC article referenced at the beginning of this article also addresses ESC and its effect on the PIT.
In summary
The Precision Immobilization Technique is a useful and usually safe procedure for ending vehicle pursuits without causing injury or substantial property damage. Officers using the PIT need to be mindful of the parameters put in place by their agencies and the dangers that can come with going outside the envelope of agency policy or procedures” especially with regard to speed.
Bibliography
Burleson T, Covelli E, Westerberg S, Brady M. September 2015. Effects of Electronic Stability Control on the Pursuit Intervention Technique. Portland Police Bureau Training Division.
Giovengo R, Tortorell P. January 2017. Electronic Stability Control and the Precision Immobilization Technique.
Zhou J, Lu J, Peng H. October 2008. Vehicle Dynamics in Response to the Maneuver of Precision Immobilization Technique. 2008 ASME Dynamic Systems and Control Conference.
