Designing in-vehicle signs for connected vehicle features: Does appropriateness guarantee comprehension?

This paper discusses the design and evaluation of connected and cooperative vehicle in-vehicle sign designs displayed on a mobile phone: Emergency Electronic Brake Lights (EEBL), Emergency Vehicle Warning (EVW), Traffic Condition Warning, and Road Works Warning. Appropriateness and comprehension of each design alternative were assessed using quantitative (i.e. Likert scales) and qualitative (i.e. open-ended questions) methods. Forty-four participants took part in the study and were shown twelve dashboard camera videos presenting a total of eleven designs alternatives, displayed with or without a legend. Despite their appropriateness, EEBL and EVW signs displayed with a legend were better comprehended and less ambiguous than those displayed without a legend. Moreover, displaying a legend below the signs to warn drivers of an emergency braking ahead was efficient in low visibility condition and could potentially increase safety in critical situations. •Designs based on existing ISO sign standards illustrating connected vehicle features were not always deemed the most appropriate by drivers.•Displaying a legend along with both the emergency braking and vehicle signs supported drivers' expected responses.•There is a discrepancy between new traffic signs design's appropriateness and comprehension.•Despite being rated as appropriate by participants, some signs were not properly understood.