Driving impairments are any conditions or actions that prevent a driver from operating a vehicle in a safe and reasonable way. They include such things as driving under the influence of alcohol or drugs, obstructed views and various conditions related to distracted driving. Generally, there are laws against actions and conditions that could lead to impaired driving conditions. As a stipulation to being licensed to drive, motorists must know and agree to abide by the laws in their area before operating a motor vehicle.
One of the most common causes of driving impairments is alcohol use. When using alcohol, reaction times, balance, and vision can all become inhibited, leading to problems while driving. While everyone may react to alcohol a little differently, most jurisdictions put a limit on the amount of alcohol that can be in someone's blood while operating a motor vehicle. Generally, the blood alcohol percentage can be no more than .08 to 1 in most jurisdictions, which is expressed in some countries as 80 to 100 milligrams of alcohol per 100 milliliters of blood.
Drugs, both legal and illegal, can have similar effects to alcohol, and therefore those individuals on some medications should refrain from driving. While it it is often overlooked, many jurisdictions consider certain medications to be serious driving impairments. It could be just as illegal to drive with those in a person's system as it would be alcohol. Often, medications that impair driving often list that as a side effect on the warning label.
Another one of the common driving impairments is having an obstructed view, which is also illegal in most jurisdictions. This can apply to having a windshield that is frosted over and cleared only in one small section. It can also be something that is inside the vehicle with the driver that may be obstructing their view, such as a piece of cargo that blocks a window. If this is against the law in an area, it may be up to a law enforcement officer to determine whether the situation presented enough of a risk that the operator could not safely operate the vehicle.
Driving impairments could also be other types of distractions such as cell phone use, eating, or grooming. Generally, laws vary regarding these types of activities by drivers. If the activity is suspected as causing an accident, then the driver being distracted will typically be the one charged with being at fault in the accident.
Criminal penalties for driving impairments depend greatly on the situation and jurisdiction. Many locations may impose a mandatory minimum jail stay for those convicted of even a first offense of driving under the influence of alcohol. Penalties may also increase based on number of offenses, and whether the offense resulted in an accident with injuries or death.