Highway is typically defined as the entire width between the boundary lines of every way or place of any type where any part thereof is open to public use for purposes of vehicular traffic. Highway has been interpreted to include a parking lot if it is open to public use. The essential feature of public use is that it is not confined to privileged individuals or groups whose eligibility is decided by some predetermined criteria, but is open to the indefinite public. For example, a taxi cab employee parking lot that is posted as "no trespassing" was held not open to public use and thus not a highway within the definition of the DUI statute. Similarly, a store parking lot restricted to employee and customer use was not a designated "open to public" parking area and thus was also not a highway under the terms of the DUI statute.

Parking lots for apartment buildings have generally been held to have sufficient "public use" to come within the highway definition regardless of the fact that they are restricted to tenants and their guests. Condominium parking lots open to the public fall into the same category. Parking lots to social clubs, bars and banks have all been held subject to the DUI laws. However, testimony must be presented showing the nature of the parking lot to sustain a conviction.

Courts are divided on whether public access areas include private property. A public access area has been interpreted to include any parking area in common public use with the owner's consent. A baseball field has been held not to be a place where the public is invited or licensed to operate a vehicle. Clearly a private residence driveway is not open to the public.

On occasion, parking lots in general have been held not to be included within the highway definition, simply because the legislature has not specifically included them within the statutory definition of "highway." Since "parking lot" was excluded from the definition of "highway" the court refused to include it in the prosecution for driving with a suspended license on a highway. In fact, a conviction was actually reversed where the offense occurred within an alley, since the term "highway" was not sufficiently defined in the felonious driving statute.