On the road and on the web? Comprehension of synthetic and human speech while driving

In this study 24 participants drove a simulator while listening to three types of messages in both synthesized speech and recorded human speech. The messages consisted of short navigation messages, medium length (approximately 100 words) email messages, and longer news stories (approximately 200 words). After each message the participant was presented with a series of multiple choice questions to measure comprehension of the message. Driving performance was recorded. Findings show that for the low driving workload conditions in the study, (cruise control, predictable two-lane road with no intersections, invariant lead car) driving performance was not affected by listening to messages. This was true for both the synthesized speech and natural speech. Comprehension of messages in synthetic speech was significantly lower than for recorded human speech for all message types. Copyright 2001 ACM.