In June 2002, the ArizonaAttorney General and Ford Motor Company assembled a Blue Ribbon Panel to review and recommend improvements to police practices in traffic patrol situations. In an initial step to gather basic information, the panel conducted a survey to identify current traffic patrol practices used by law enforcement agencies. The panel has used these initial findings as well as input from NHTSA and the Ford Motor Company to develop best practice recommendations to improve officer safety.
Analysis of responses dealing with traffic stops by officers from 80 agencies, including 47 police departments, and 29 state-level patrol agencies shows:
- 75% park vehicles offset left when making a traffic stop
- 72.5% park in the rear of the stopped vehicle
- 65% say their officers approach a stopped vehicle on the driver's side
- 46.2% report turning the wheels to the left
This research paper does not suggest how an officer should position their vehicle in a traffic stop as that is a tactical decision. If the officer positions the police vehicle offset left, as 75% of the survey respondents do, there are positioning considerations that are projected to improve officer safety that this paper will describe. Please note that the positioning considerations addressed in this paper were only studied for rear wheel drive (RWD) vehicles. Front wheel drive (FWD) or 4x4 police vehicles were not studied and may have different steering response in an accident as the front wheels would not always rotate in a crash.
Officers place themselves in danger by leaving the relative safety of their vehicles and standing several feet from moving traffic to establish contact with a stopped vehicle. Officer fatalities as pedestrians account for 9% of all officer fatalities. To minimize risk of errant vehicle strikes, pedestrian police officer contact with a stopped vehicle should occur as far away from traffic as possible, such as at a rest stop, service drive, in a driveway or parking lot, etc. When conditions prevent this, contact with the stopped vehicle should occur as far onto the right shoulder of the road or highway as possible, farthest away from the fastest moving traffic, avoiding stops in the median and in any lane of travel. Additionally, officers should stand 6 feet from the passenger door of the rear vehicle, usually the police car, whenever possible. Weather or other conditions may prevent standing outside but this presents the least risk position for a pedestrian. When this is not possible, officers should minimize the amount of time spent in the stopped police vehicle to minimize their risk for injury in an errant vehicle collision. Furthermore, adoption of an orientation described in the paper for offset left stops is projected to achieve a reduction in injuries and fatalities suffered by police officers when they are pedestrians in a roadside stop.
Offset Left Stops
Positioning the police vehicle to improve the protection of the pedestrian officer from a striking vehicle is only one of the factors to be considered in police traffic stop procedures. Balancing this risk with the others inherent in police work is beyond the scope of this study and is a task left to law enforcement professionals. However, the consideration of a certain orientation procedure noted in this paper is likely to reduce pedestrian officer fatalities due to errant vehicle strikes in offset left parking situations.
Reduction of the number of injuries and fatalities suffered by police officers can be achieved with certain orientation procedures for police vehicles. The recommendations in this paper apply to stops behind vehicles with the officer parking offset left with a driver door approach.
Technical Discussion - Computer Simulation Configurations
Based on the results of the survey, Ford Motor Company utilized innovative computer simulation tools to research various stopped vehicle/police vehicle/striking vehicle configurations. Simulations of officer position at the right and left side stopped vehicle doors were conducted. Initial simulations indicated that attempting to protect for officer approaches on both sides of the stopped vehicle compromises the protection that can be provided by a configuration tailored to a single-side approach only. An offset left position is described in this paper as this configuration provides vehicle coverage for the pedestrian police officer from errant traffic, and it was the approach preference of 75% of the survey respondents. Three common configurations were initially used. The first configuration consisted of the police vehicle parked behind a stopped vehicle with an overlap of 20% to 100% (where 100% represents the police vehicle parked directly behind and inline with the stopped vehicle), the police vehicle parallel to the road with a steering angle of zero degrees, and distances of 3 to 15 feet between the stopped vehicle and the police vehicle. The second and third configurations were similar with the police vehicle angle to the road varying from 15 to 30 degrees either away from or towards the road and the police vehicle steering angle ranging from 25 degrees either right or left.
Technical Discussion - Simplifying Assumptions
To facilitate reasonable conclusions, foundational assumptions were required to determine a preferred orientation. Dry and level road surfaces were assumed for all simulations. The stopped vehicle and its wheels were oriented parallel to the direction of travel of the roadway with the ignition switch off, thereby locking the steering wheel. Furthermore, the left side of the stopped vehicle was at least one vehicle width from the right border of the closest lane of travel. The police vehicle was a RWD configuration with the gear selector in park, the parking brake applied, and the steering wheel unlocked, simulating an idling in park condition. The weight range of striking vehicles was limited to passenger cars and light trucks and these vehicles experienced no significant steering input during the crash event. Not included in the simulation were rigid barriers, guardrails, retaining walls, curbs, mature trees, etc. in the immediate vicinity or post-crash path of the stopped vehicle and police vehicle.
Findings
Initial findings resulted in an optimized vehicle orientation based upon physical principles. A physical crash test was conducted with vehicles positioned as shown below. The stopped and police vehicle trajectories proceeded as the simulation predicted though the striking vehicle deviated from the simulated path. Upon review of this result, several details such as collision-induced steering, vehicle hop, wheel/tire damage, etc. were incorporated into the simulation and resulted in concurrence with the physical results, thereby validating the capability of the computer simulation. This orientation suggests the highest probability of diverting an inbound vehicle to avoid hitting the pedestrian officer in the most robust fashion. This configuration is shown below.
The dynamics of a hypothetical collision certainly cannot be known in advance nor can a single vehicle orientation be expected to provide uniform protection for the pedestrian officer in a dynamic environment. Further computer simulations and a verifying physical crash test were conducted with vehicles in the configuration shown. The police vehicle is parked at least fifteen feet behind a stopped vehicle with a 50% overlap (offset left) between the vehicles. In this illustration, the position of the pedestrian officer near the driver side door of the stopped vehicle is shown as an X. The police vehicle is shown being struck from behind by a striking vehicle. Note that the wheels of the police vehicle are turned to the right.
Proposed Positioning for Offset Left Stops
This orientation was shown to provide coverage for the pedestrian police officer. In the event of a collision between a striking vehicle and the police vehicle, the angle of the police vehicle wheels steer the vehicle away from the pedestrian officer while the spacing of at least 15 feet or one car length allow enough distance for the police vehicle to track away from the pedestrian officer. The left offset and overlap between the police vehicle and the stopped vehicle provides coverage for the pedestrian officer from oncoming traffic. Orienting the police vehicle parallel to the roadway presents the smallest target for an errant vehicle yet still protects the officer. As compared to the other configurations tested, the above orientation resulted in the highest probability of a pedestrian police officer avoiding involvement in the accident, a result 3 times higher than some of the other configurations tested.
Recommendation
The safest position for stopping a vehicle is to move the stopped vehicle off the roadway as far from moving traffic as possible. If that is not possible and if the officer has chosen the offset left position for stopping a vehicle, the best protection for a pedestrian officer while he is at the stopped vehicle driver's door is to position the vehicle as follows: Space the vehicle about 15 feet (1 car length) away, Turn the steering wheel to the right and be Overlap with the stopped vehicle 50% Parallel to the road. To recall this police vehicle positioning, the following acronym was developed:
S Space between vehicles about 1 car length or at least 15'
T Turn Steering Wheel Full Right
O Overlap with stopped car approx. 50%
P Parallel to the Roadway