Dynamic is optimal: Effect of three alternative auto-complete on the usability of in-vehicle dialing displays and driver distraction

Abstract

Objective Auto-complete (AC) has become ubiquitous on domain-specific systems and is mainly divided into two types (static-AC and dynamic-AC). Specifically, static-AC only presents the possible completions not changing with user input in the suggestion list for users to select. Dynamic-AC constantly filters out inconsistent content with user input and shows the possible completions at the top of the suggestion list. However, the details of the driver’s interactions with AC in the vehicle are poorly understood. Therefore, we investigated the effect of three alternative AC (non-AC, static-AC, and dynamic-AC) on the usability of in-vehicle dialing displays and driver distraction. As a reference, the baseline task (only driving) was also surveyed in each AC condition. Methods A simulated driving experiment consisting of 24 participants was conducted. The primary task was a lane-keeping task with speed ranging between 60 and 120 km/h over the stretch. The secondary task was dialing an 11-digit phone number. Usability metrics (task completion time and number of errors) and driver distraction metrics (NASA-reduced task load index (NASA-RTLX), mean speed, lateral position variation, total glance time, number of glances, mean glance time, and number of glances over 1.6 s) in each condition were measured. A series of one-way repeated measure analyses of variance was used to examine whether and which type of AC can maximize the usability of in-vehicle dialing displays and minimize driver distraction. Results Generally, the AC-based in-vehicle dialing display gains a more positive effect. Specifically, we observed that among the three alternative AC conditions, dynamic-AC performed optimally on usability metrics similar to previous studies and various driver distraction metrics, notwithstanding it is still not up to the level of the baseline condition. However, static-AC did not exhibit the advantages described in previous studies except for fewer errors and NASA-RTLX owing to the possibility of position bias and boundary effect. Conclusions This study provides valuable insights into drivers’ interactions with AC-based in-vehicle dialing displays and broadened its applications in safety-critical situations. More importantly, it informs the design of a more effective in-vehicle system, which positively contributes to mitigating driver distraction and preventing traffic accidents.