Evaluation of Manual vs. Speech Input When Using a Driver Information System in Real Traffic

The executed study evaluated the influence of manual and speech input on driving quality, stress and strain situation and user acceptance when using a Driver Information System (DIS). The study is part of the EU-project SENECA. 16 subjects took part in the investigations. A car was equipped with a modified DIS to carry out the evaluation in real traffic situations. The used DIS is a standard product with manual input control elements. This DIS was extended by a speech input system with a speaker independent speech recogniser. For the use of the different DIS devices (radio, CD player, telephone, navigation) 12 different representative tasks were given to the subjects. Independently the type of task speech input needs longer operation times than manual input. In case of complex tasks a distinct improvement of the driving quality can be observed with speech instead of manual input. The subjective safety feeling is stronger with speech than with manual input. With speech input the number of glances at the mirrors and aside is clearly higher than with manual input. The most frequent user errors can be explained by problems when spelling and by the selection of wrong speech commands. The rate of speech recognition errors amounts on the average to 20.6 % what makes it necessary to increase the recognition performance of the examined speech system. This improvement of system performance is the task of the development for the system demonstrator in the 2nd half of the SENECA project