Lassen means "to leave behind" something that is retrievable. It can either be an act of will or of forgetfulness. Lassen always takes an object.
 

Abfahren or losfahren mean "to depart" and imply a motorized conveyance, but not an airplane, for which abfliegen is used. Losfahren, abfahren and abfliegen never take an object, though they may include a prepositional phrase with von.
 

Verlassen means "to abandon" or "to forsake" a person or "to leave" a building, a city, a neighborhood, or a country, that is, things too massive or conceptual to be retrievable.