http://www.nhtsa.gov/people/injury/enforce/deskbk.html#UVMVPart Three: Setting Policy for Successful Traffic Enforcement Setting Policy for Successful Traffic Enforcement
The Motorcycle as a Traffic Enforcement Tool
Unmarked vs Marked Vehicles Use of Aircraft for Traffic Enforcement
Marked Vehicles
Advantages:
Fully marked patrol vehicles provide high visibility to the motoring public and serve a two-fold purpose: Not only is a deterrent factor provided, but the public can readily identify a source of help during time of need.
paramount value is the physical protection provided by a fully marked patrol car. A light bar, spotlight and full markings offer maximum visibility, whether the officer is conducting a routine traffic stop or providing assistance along the highway. At the scene of traffic collisions or any blockage of the roadway, the protection provided by fully marked units is most valuable. Its presence not only offers physical protection to the officer and citizens at a scene but so warns aproaching traffic.
The fully marked patrol car also keeps liability to a minimum. It is obvious and indisputable in its authority. While the full markings and light bar offer an important safety element in a pursuit, they also ensure compliance with statutory requirements for felony charges of eluding pursuit (i.e., the defendant knew that it was a police officer attempting to stop him).
Disadvantages:
The light bars on the marked vehicle, because of wind resistance, negatively affect acceleration and top speed as well as fuel economy.
By virtue of their high visibility, fully marked vehicles create a “halo effect” within their immediate vicinity.
Violations, especially flagrant ones, occur less frequently in their presence. Experience indicates that the duration of the “halo effect” is relatively short-lived in the absence of the marked vehicle.
Unmarked Vehicles
Advantages:
Unmarked patrol cars offer, to some degree, stealth and anonymity. Within a police fleet, they can be valuable for travel, inconspicuous transport details, and non-line and supervisory or command transportation, as well as traffic functions.
As a traffic enforcement tool, unmarked vehicles may expose the officer to more frequent as well as more flagrant violations.
They can be especially valuable when used in the capacity of an “emphasis patrol” where chronic violators are being targeted.
Excessive speed, truck violations, radar detector reliance and erratic drivers can all be targeted with the unmarked patrol vehicle.
As previously noted, improved performance and economy are also a benefit of the patrol vehicle operated without the light bar.
Oddly enough, according to one Illinois survey, the semi-marked vehicle (no light bar) actually holds one safety advantage over the fully marked vehicle. This survey indicates that not only were proportionately fewer semi-marked vehicles involved in collisions, but they averaged less damage than their marked counterparts. The explanation suggested for this phenomenon was that police officers assume that roof-mounted emergency lights project unchallenged authority. When the light bar is removed, the officer has to become a more cautious driver.
Disadvantages:
Among the concerns with the totally unmarked vehicle are that they offer less visibility when responding to an emergency or when protecting an accident scene or traffic stop, especially when 360- degree protection or visibility on a high-speed highway from some distance down the road is required. Some argue, however, that the difference in safety at an accident scene is not as statistically significant as one might assume.
The unmarked vehicle does not immediately project the authority that the fully marked vehicle does. This reality may present particular problems in certain situations, such as a pursuit, where it is necessary to warn oncoming traffic of the presence of the police vehicle, or when stopping lone female occupants or persons who are carrying valuable cargo. The possibility of someone impersonating a police officer is greater in jurisdictions where unmarked units are used for traffic patrol.
The incorporation of unmarked vehicles into a police fleet also decreases the uniformity of the fleet, and makes it more difficult to investigate citizen complaints of officer misconduct with official vehicles.
Additional Considerations......