11. An apparatus for controlling a vehicle, comprising: an input arranged to receive one or more instructions issued as speech; a memory arranged to store the received speech; a speech recognition module arranged to analyze the speech to provide a sequence of words and a word confidence measure for each word recognized; a natural language understanding module arranged to receive the sequence of words and the word confidence measures, and analyze the sequence of words to identify a semantic concept corresponding to an instruction based on the analysis and a semantic confidence level for the identified semantic concept derived at least in part with reference to the word confidence measures of the words associated with the semantic concept; a response generation module arranged to provide a spoken confirmation of the identified semantic concept based on the semantic confidence level and an indicated verbosity level; and a command generation module arranged to use the identified semantic concept to provide a control input for the vehicle; wherein the response generation module is arranged to provide the spoken confirmation of the identified semantic concept to indicate that the instruction was not understood when the semantic confidence level is below a threshold, or the command generation module is arranged to use the identified semantic concept to provide a control input for the vehicle when the semantic confidence level exceeds the threshold, and the response generation module is arranged to provide the spoken confirmation of the identified semantic concept with at least one of a speaking rate or a pitch that is increased as the indicated verbosity level decreases.
11. An apparatus for controlling a vehicle, comprising: an input arranged to receive one or more instructions issued as speech; a memory arranged to store the received speech; a speech recognition module arranged to analyze the speech to provide a sequence of words and a word confidence measure for each word recognized; a natural language understanding module arranged to receive the sequence of words and the word confidence measures, and analyze the sequence of words to identify a semantic concept corresponding to an instruction based on the analysis and a semantic confidence level for the identified semantic concept derived at least in part with reference to the word confidence measures of the words associated with the semantic concept; a response generation module arranged to provide a spoken confirmation of the identified semantic concept based on the semantic confidence level and an indicated verbosity level; and a command generation module arranged to use the identified semantic concept to provide a control input for the vehicle; wherein the response generation module is arranged to provide the spoken confirmation of the identified semantic concept to indicate that the instruction was not understood when the semantic confidence level is below a threshold, or the command generation module is arranged to use the identified semantic concept to provide a control input for the vehicle when the semantic confidence level exceeds the threshold, and the response generation module is arranged to provide the spoken confirmation of the identified semantic concept with at least one of a speaking rate or a pitch that is increased as the indicated verbosity level decreases. 13. The apparatus of claim 11 , further comprising a language model database operably coupled to the speech recognition module, wherein the language model database has data stored therein that provides information about the most likely sequences of words expected to be found.