Study: How to maneuver suspects to a stop
By Becky Lewis
The police cruiser closes in on the fleeing suspect vehicle and sends it into a spinning stop as the backup vehicles close in and surround it, preventing escape. That’s the way it happens in the movies and on television, anyway.
In reality, law enforcement officers know that the PIT Maneuver is an extremely dangerous tactic with a small window of effectiveness, and recent research by the National Institute of Justice (NIJ) Weapons and Protective Systems Technology Center of Excellence (WPSTC) attempts to quantify its potential for effective employment.
In October 2012, WPSTC Pursuit Management Technology staff partnered with the Michigan State Police (MSP) Precision Driving Unit (part of the state police academy) to characterize vehicle dynamics during the use of the PIT Maneuver. Their principal concern was the behavior of vehicles equipped with electronic stability control technology. Using a combination of vehicle types (neither car with electronic stability, both with electronic stability), instructors and students from the MSP’s Pit Maneuver Training Courses ran vehicles through the test protocol at a variety of speeds. WPSTC compiled results using Video VBOX, a commercially available data collection system, to capture the behavior of vehicles during testing via both video and data.
Engineering Project Manager Mike Hendrickson says that finding the appropriate testing venue and vehicles proved the biggest stumbling blocks in conducting the testing, and the partnership with MSP not only provided the right kind of course, it also gave the center access to the Dodge Chargers and Ford Crown Victorias commonly used by law enforcement agencies. (MSP conducts annual testing of new police vehicle models and has an ongoing relationship with the manufacturing community.) VBOX USA also contributed to creating the right testing environment by renting its GPS-based equipment to WPSTC and providing a technician who assisted with data collection.
“The number-one thing we looked at in the study was the difference between vehicle dynamics in cars that have electronic stability control systems and cars that do not,” Hendrickson says.
Over a period of four days, WPSTC instrumented five different types of vehicles, starting with an MSP vehicle used during a pursuit course being conducted at the same time as the testing. Researchers used results from this car as a baseline for comparison, then conducted testing on the other vehicles to obtain stability control comparison results. Key observations include:
1. The amount of steering input required of the pursuit vehicle to induce an effective spin is dependent on whether the target vehicle is equipped with stability control technology; interestingly, employing PIT at lower speeds with aggressive steering input caused significant damage to the target vehicle.
2. In a vehicle equipped with stability control, it is imperative that the steering input occurs after the pursuing vehicle’s front bumper has “mated” with the target vehicle’s rear bumper; “Double Tap” impacts are likely and serious damage to both vehicles is possible if the PIT maneuver is employed incorrectly.
We weren’t trying to come back with recommendations on what law enforcement should do,” Hendrickson says. “We observed and characterized our observations scientifically so agencies can make informed decisions on employment and pursuit policy. They could possibly use these results to determine whether to change their tactics, such as deciding whether to use the PIT Maneuver at various speeds.”
Testing came about as the result of meetings between the WPSTC’s Pursuit Management Technology Working Group (TWG) and the instructors at the Federal Law Enforcement Training Center (FLETC), whose members and respective agencies had serious questions about the effectiveness of the PIT Maneuver against vehicles with stability control. Lt. Jim Flegel, director of the MSP Precision Driving Unit and a member of the Pursuit Management TWG, facilitated the testing by providing the venue and driving instructors. WPSTC staff compiled results during the remainder of 2012. A 15-minute DVD and a more detailed technical report will be released in 2013.Theirreleasewill be announced via www.justnet.org, the website of the National Law Enforcement and Corrections Technology Center System and its social media channels.
During initial research, WPSTC researchers uncovered a study from the University of Michigan, “Active Safety Measures for Vehicles Involved in Light Vehicle to Vehicle Impacts,” by Ph.D. candidate Jing Zhou that used computer simulations to model the behavior of target vehicles equipped with electronic stability control during the PIT Maneuver. This study, coupled with research conducted by FLETC, served as a starting point for actual vehicle dynamics testing.
During the FLETC project, researchers examined why students trained in the electronic stability control equipped Dodge Charger experienced catastrophic accidents when they moved back into the Ford Crown Victoria. They determined that students had learned to drive a more technologically advanced vehicle faster and more aggressively with no negative results. As a result of these findings, FLETC also looked at how stability control technology could impact the use of PIT. Both the University of Michigan study and the FLETC project provided anecdotal evidence that vehicles equipped with stability control would behave differently during a PIT Maneuver.
“FLETC conducted a basic study with cameras and instructors. They didn’t instrument the vehicles,” says Hendrickson. “We wanted to move the research one step further. Now that we’ve done actual research with the Crown Vics and the Chargers, we’d like to do some further research, similar to the University of Michigan study, using CarSim®, which will create a computer model for any type of vehicle.”
For more information on the PIT Maneuver project, contact Mike Hendrickson, WPSTC Focus Area Manager for Pursuit Management Technology, at (814) 865-1289 or firstname.lastname@example.org. For more information on the Weapons and Protective Systems Technology Center of Excellence, contact NIJ Program Manager Brian Montgomery at (202) 353-9786 or email@example.com.
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