Date of Award

December 2020

Document Type


Degree Name

Doctor of Philosophy (PhD)


Automotive Engineering

Committee Member

Johnell O Brooks

Committee Member

Yunyi Jia

Committee Member

Robert G Prucka

Committee Member

Patrick J Rosopa


The purpose of this research was to evaluate drivers’ understanding of automotive symbols meaning and what action to take in response to a symbol. With the dramatic increase in vehicle technology, the availability of a wide range of powertrain options, and the development of advanced driver assistant systems (ADAS), instrument cluster interfaces have become more complex, increasing the demand on drivers. Understanding the needs and preferences of a diverse group of drivers is essential for the development of digital instrument cluster interfaces that improve driver’s understanding of critical information about the vehicle. This research was divided in three studies. Study I evaluated teen drivers’, between 15 to 17 years of age, understanding of symbols from vehicles featuring advanced driving assistant systems and multiple powertrain configurations. The teenage driver population was selected for this study because in the U.S., the teenage driving population is at the highest risk of being involved in a crash. Teens often demonstrate poor vehicle control skills and poor ability to identify hazards, thus proper understanding of automotive indicators and warnings may be even more critical for this population. In addition, teen drivers are usually not represented in automotive symbol comprehension studies. In this research, teen drivers’ (N=72) understanding of automotive symbols was compared to three other groups with specialized driving experience and technical knowledge: automotive engineering graduate students (N=48), driver rehabilitation specialists (N=16), and performance driving instructors (N=15). Participants matched 42 symbols to their descriptions and then selected the five symbols they considered most important. Teen drivers demonstrated lower performance (Mean=29%) identifying symbols than the other three groups (Mean=60%). For all groups, responses on symbols related to basic vehicle functions and common to all powertrain types had significantly higher scores than symbols related to advanced driving assistant system (ADAS) functions or those that are powertrain specific. Overall, the five symbols selected by the participants as most important were related to powertrain and safety warnings. Study II investigated drivers’ understanding, and preferences related to powertrain and ADAS symbols presented on instrument clusters. Participants answered questions that evaluated nine symbol’s comprehension, familiarity, and helpfulness. Then, participants were presented with information from the owner’s manual for each symbol and responded if the information changed their understanding of the symbol. Lastly, participants rated their need for more information to understand the symbols and shared their preferences about how the automotive interface could help them better understand the symbols. Teen drivers (N=30), normal drivers (N=20), driving rehabilitation specialists (N=20), and automotive engineering students (N=48) participated in this study. When comparing the groups’ performance on the comprehension testing, driving rehabilitation specialists had the best performance. Teen drivers had the poorest performance. Symbols with an implied or arbitrary icon-function relationship demonstrated poorer comprehension for all participant groups. Symbols with a direct icon-function relationship received higher comprehension scores and helpfulness ratings independent of previous exposure. Symbols considered less helpful received higher ratings on the need for additional information, suggesting that drivers need additional information to understand the symbol when the symbol meaning is not clear. Automotive engineering students and normal drivers reported being considerably less satisfied with the information presented on the dashboard of their vehicles. Study III investigated drivers’ understanding of six automotive symbols presented on the instrument cluster or infotainment screen on a driving simulator study. Teens drivers between 15 to 17 years of age (N=24), adult drivers between 30 to 54 years (N=24), and senior drivers between 65 to 80 years of age participated in this study. The results of this driving simulator study suggest that presenting automotive symbols on in-vehicle displays with text description improved driver’s understanding of symbols meaning and what action to take in response to a symbol. Symbol type and previous experience with the symbol were contributing factors on symbol comprehension. Participants reported having higher previous experience with the powertrain symbols than the ADAS symbols and in general demonstrated significantly better understanding of symbols meaning and what action to take in response to powertrain symbols than ADAS symbols. Driving experience was not observed to be a contributing factor to correctly identifying a symbols’ meaning nor what action to take in response to the symbol in this study. Mixed evidence was observed on the negative impact of text descriptions on driving performance. Performance on the driving simulator and cognitive workload measures of mean and maximum index of cognitive activity (ICA) suggest that text descriptions did not negatively impact driving performance. On the other hand, eye glance off the road time, symbol reaction times, and the self-reported cognitive workload measures suggest that text descriptions negatively impact driving performance. Further research is needed to evaluate the impact of text descriptions on driving performance. In the end, participants demonstrated to prefer having more information about the symbols presented at the in-vehicle displays both when driving and while stopped. The inclusion of the teenage driver population under 18 years in future symbol comprehension testing studies and the exploration of alternative methods to communicate vehicle information to the driver should be considered by vehicle manufacturers. The results of this study may help automotive professionals when developing new vehicle interfaces to aid inexperienced and experienced drivers. The results of this study may help when developing new vehicle interfaces, ensuring that indicators and warnings are presented in a way that aid both inexperienced and experienced drivers. Overall, this study demonstrates that the evaluation of symbol’s comprehension and the comparison of alternative methods to communicate information on the in-vehicle displays greatly benefit from testing on a dynamic setting using a driving simulator versus a paper and pen survey. The dynamic setting allowed a comprehensive analysis of the effects of powertrain and ADAS warning symbols on driver’s understanding of the symbol, driving performance, and preference.



To view the content in your browser, please download Adobe Reader or, alternately,
you may Download the file to your hard drive.

NOTE: The latest versions of Adobe Reader do not support viewing PDF files within Firefox on Mac OS and if you are using a modern (Intel) Mac, there is no official plugin for viewing PDF files within the browser window.