  Driver distraction has become a major threat to the road safety, and the
globally booming taxi-hailing application introduces new source of distraction
to drivers. Although various in-vehicle information systems (IVIS) have been
studied extensively, no documentation exists objectively measuring the extent
to which interacting with taxi-hailing application during driving impacts
drivers' behavior. To fill this gap, a simulator-based study was conducted to
synthetically compare the effects that different output modalities (visual,
audio, combined visual-audio) and input modalities (baseline, manual, speech)
imposed on the driving performance. The results show that the visual output
introduced more negative effects on driving performance compared to audio
output. In the combined output, visual component dominated the effects imposed
on the longitudinal control and hazard detection; audio component only
exacerbated the negative effects of visual component on the lateral control.
Speech input modality was overall less detrimental to driving performance than
manual input modality, especially reflected in the drivers' quicker reaction to
hazard events. The visual-manual interaction modality most severely impaired
the hazard detecting ability, while also led to strong compensative behaviors.
The audio-speech and visual-speech modality associated with more smooth lateral
control and faster response to hazard events respectively compared to other
modality. These results could be applied to improve the design of not only the
taxi-hailing application, but also other input-output balanced IVIS.
