Ergonomics can be defined as the applied science of equipment design. In short, the science of why your computer keyboard is at the angle it is or why that chair lump juts into your lower back. Ergonomics can be understood by knowing the reasons why someone decided to put a button in one place and not another.
Three factors — comfort; convenience and safety — form the idea of good ergonomics for each tool and piece of equipment. These factors are also considered in police vehicle design. No matter how much one fiddles with his Blackberry while driving, not many people use their vehicle as a mobile office more than law enforcement officers. For this reason, officers must spend their days in vehicles with a well thought out ergonomic design. Fortunately, patrol vehicle manufacturers study ergonomics with the law enforcement official in mind.
"Since the vehicle is essentially a mobile office, we want officers to be comfortable," says Sgt. Keith Wilson of the Michigan State Police and test driver for the Michigan State Police Vehicle (MSP) Vehicle Tests. "That consists of comfortable seating, room for their equipment, easy access to instrumentation, easy view of instrumentation and enough room to install equipment such as radars, cameras, computers, guns and things of that nature."
The comfort of officers and the twisting involved in using mobile office equipment are both a concern for vehicle manufacturers. "While different departments use laptops for different things … there is an ergonomic problem from having a computer at a 45-degree angle to the driver," says Michael Blackmer, special vehicle engineering supervisor of Ford Motor Co. "This forces the driver to twist his body [to use the equipment] even though his legs stay forward. These are all considerations that come into play when making a vehicle into a mobile office."
Officers must be able to reach equipment such as laptops, monitors and printers comfortably and safely. When ergonomics is not considered in vehicle design or in the installation of this technology, accessing this equipment causes officers to uncomfortably twist their upper body, putting pressure on the ligaments of the lower back.
"The body is not designed to twist like that," says Dr. Cheryl Mittelstedt, a Fort Atkinson, Wisconsin-based chiropractor with 22 years of experience. "However the body is designed to make corrections every time you move." She continues to explain that keeping one body segment stationary while moving the rest creates unnecessary strain. Constant wear and tear can weaken the thin ligaments in the lower back, allowing the discs to shift. This altered biomechanical state can place pressure on or cause irritation to the nerves that create the sciatic nerve.Ergonomics issues in the mobile office
The officer keeping his watchful eye on traffic driving by values his vehicle's ergonomics more than the placement of controls and where equipment can be mounted.
Lt. Brian Moran, fleet manager of the Los Angeles County Sheriff's Department and head of the Los Angeles Sheriff's Department Police Vehicle (LASD) Vehicle Tests, views ergonomics as it relates to comfort: how the officer can get in and out of the car, how comfortable it is to work in, and whether it lends him the ability to do his job effectively.
"The concern is not always how comfortable it is to sit in, but whether the vehicle provides the ability to accelerate in order to respond in an emergency traffic situation," Moran adds.
Considerations also arise over the equipment officers wear on their duty belts. When a right-handed officer wears his weapon on his right side, the holster can interfere with the seat belt. This can cause the holster to become unsnapped or entangled in the belt when exiting the vehicle.
However, the officer is backed by vehicle manufacturers, which respond to common design faults and complaints from law enforcement officers. For instance, Ford previously designed a seat with the padding carved out from the bottom of the seat back, providing additional room for the officer's weapon and handheld radio. "An important thing we can do for [officers] is to keep them comfortable, because they are sitting in that seat so much," Blackmer stresses.
The vehicle's ergonomic design becomes more complicated with the addition of communications, computer and accessory mounts. Knowing that each agency sets up its patrol vehicles differently, vehicle manufacturers face challenges when it comes to balancing efficient communications and smart ergonomic design. "When an agency or department purchases a laptop mount, this creates a couple of problems and some risk," explains Blackmer. "When it's opened, it could block out the radio, which might be bothersome. It could block the trunk-release button, the climate control, ashtray, cup holders or anything on that center stack." Ultimately, since the mount is an aftermarket purchase, departments installing any additional equipment should weigh access to communications and accessories versus the convenience of the mount.
Major vehicle manufacturers, such as Ford, Chrysler and General Motors Corp., employ police advisory boards to act as a liaison and a resource for other law enforcement agencies. According to Moran, a member of all three manufacturer advisory boards, officer safety has also been discussed as it pertains to airbag deployment and the relationship of different mounts and equipment.
Law enforcement should consider where they mount equipment with the airbag positioning in mind. "It is possible for something struck by an airbag to become a projectile inside the car when the airbags deploy," Wilson says.
Aside from flying laptops and print mount projectiles, another airbag-related issue is the likely integration of side-curtain airbags into future vehicle models in order to pass the side-pole crash test in effect beginning with the 2013 model year. These airbags inflate across the full window area to protect passengers in all outboard seating positions in a side-impact collision. Blackmer explains, "While there is no mandate that says you have to put curtain airbags [in the vehicle], passing the crash test will drive companies to integrate them."
He goes on to say that while there won't be a problem implementing these devices in consumer vehicles, there will be a problem in police squads. A decision will need to be made by police agencies on how to partition the front and rear seats without interfering with side-curtain airbag deployment. With a security screen installed, the airbag may not be able to inflate correctly. A simple solution may be to cut down the security screen, but doing so could allow a prisoner to gain access to the front seat.Rating comfort and convenience
With law enforcement officers sitting for a full 8- or 10-hour shift, proper vehicle ergonomics should be a major factor in choosing fleet vehicles. But for officers to make the selection themselves, each officer would need to sit for hundreds of miles in every law enforcement vehicle package to effectively compare models. Fortunately, the Michigan State Police and the Los Angeles County Sheriff's Department conduct vehicle ergonomics evaluations in addition to annual performance testing, i.e. speed, acceleration and braking.
Both the MSP and LASD Vehicle tests evaluated the Chevrolet Impala and Tahoe (the only pursuit-rated SUV included in the tests), the Dodge Magnum and Charger, and the popular Ford Crown Victoria Police Interceptor.
The resulting scores are based on the test driver's personal opinion of each particular ergonomic aspect. "[The test drivers] are dedicated individuals, they have to retain the same level of proficiency for each of the tests," says Moran.
Ergonomic evaluators are recruited from each test's regional area. Officers sit in the vehicle in full uniform for a realistic representation of how the officer's day-to-day vehicle ergonomic issues can be addressed, explains Wilson.
In the most recent MSP Tests, 10 drivers evaluated each vehicle in the same 10-mile loop. Each driver scored the vehicle's interior on a 10-point scale based on an organized ergonomic inventory. These 10 scores were averaged to minimize any bias toward one vehicle or another. Evaluation categories included the front and rear seat, instrumentation, controls, visibility, communications, and a sum total of the averaged scores. See Page 47 for the condensed results of MSP's Ergonomic Evaluation.
The MSP communication evaluation, done by the department's radio shop, rated the radio equipment accessibility in the dashboard and trunk. The radio shop also evaluated the engine compartment, considering the ease of electronic component installation under the hood and the running of cables, says Wilson. "They also did a noise check on the vehicle to evaluate how well the car is grounded from radio frequency interference," he adds.
The LASD tests evaluated each vehicle by four drivers on 100-mile course traversing different types of terrain. These tests broke down each major category into an itemized inventory to examine different aspects of a vehicle's ergonomics. "Visibility" is explained as the driver's overall forward visibility considering a number of factors such as ceiling and dashboard height, pillar placement, windshield size and distortion. Additionally, the L.A. tests examined an officer's peripheral view using "clock positions" to designate the viewing position with and without using the rearview and side mirrors.
The LASD Tests further catalog each vehicle's major category, considering particular ergonomic aspects such as head and leg room, placement and position of controls, and control accessibility and proximity to each other. See Page 52 for shortened results of the LASD tests.
L.A.'s testing also included a motorcycle ergonomic evaluation. These results can be viewed at www.lasd.org/sites/motorcycle-test once posted. Moran adds that there tends to be a stronger bias among individuals toward one brand of motorcycle. However, the scores identified individuals with such a bias in order to cancel them out and receive a fair evaluation.
While the ergonomic evaluations from both organizations are extensive, neither the LASD nor the MSP tests evaluate the safety factors of any aftermarket accessory mounts or equipment. Wilson points out that it would be hard to test for these safety factors but notes evaluating the interior room in terms of the space to install computers, radars and cameras lends itself to the safety factor.Asking for a fix
Once on the road, if an officer discovers an ergonomic design problem in the squad car, he should mention it to the agency head or department fleet manager, who should in turn mention it to the dealer the agency purchased its vehicles from. If the problem is common enough, it may be a design fault, and major vehicle manufacturers are responsive to remedying these issues.
"I can't pretend to know what [law enforcement] needs for everything they do," Blackmer admits. "This means we are really more reactive than proactive."
Whenever he plans to make a change, Blackmer says his design team meets with Ford's police advisory board to show them proposed changes to avoid making an ergonomic design mistake. However, they don't fully know how the design will work until it's tested in the field — and that's where officer input comes in.Preventing problems
Even with all these ergonomic considerations in place, enforcement officer's lower backs may still be wrenched if poor ergonomic posture continues. Improper sitting posture can lead to back problems. According to Mittelstedt, sitting applies 200 times more pressure on the lower back than standing. Sitting incorrectly can push the lumbar spine backwards, turning the spine into a "C" shape instead of its natural "S" shape. Add that amount of pressure on the lower back to the amount of hours clocked sitting in the patrol vehicle and it's easy to see the problem. Fortunately, officers can handle most comfort and twisting issues individually through proper sitting posture and preventative exercises.
It's possible to enhance a vehicle's ergonomics design with some small modifications. Mittelstedt recommends individuals keep legs and arms parallel to ground and hold their backs straight to keep their spine in its natural "S" shape. She also suggests putting foam pads between the lower back and the vehicle seat to help correct posture, but recommends removing them occasionally to keep the spine adjusting. Other ideas for better posture and health include continuing aerobic training, such as a 20-minute walk to get the joints moving and effectively lubricated; eating healthy and drinking enough water.
Vehicle manufacturers have already designed the 2008 police model packages. For the years to come, it will continue to take law enforcement's participation and manufacturers' willingness to adapt and change to keep officers comfortable in their mobile office.
Editor's note: When available, the 2008 Los Angeles County Sheriff's Department Vehicle Tests can be found at www.lasd.org. Visit www.michigan.gov/msp for the full results of the 2008 Michigan State Police Vehicle Tests.