The purpose of this research was to compare the usage of a traditional paper map and electronic route maps during driving, and to consider the effects of congestion information and map scale sizes on driving performance, workload and subjective feelings. Experiments were conducted in desktop virtual driving environments with a 17-in. color monitor simulating driving environments and a 14-in. color monitor showing different kinds of navigation systems. A total of 20 undergraduate students of National Tsing Hua University were paid to participate in the Experiment I. The criteria for driving performance were trip duration, driving speed and number of navigation errors. Heart rate was measured as an index for workload. The 5-point Likert-type questionnaire was used to reflect the perceived nervousness, fatigue and task difficulty. Results indicated that the performance difference between a paper map and electronic route maps depended on the design characteristics of electronic route maps. Comparisons among four electronic maps revealed two significant main effects of congestion information and scale sizes on trip duration. Besides, it seemed that the availability of congestion information was useful for reducing navigation errors. Neither statistically significant main effects nor interaction was found on subjective feelings and driving speed. Another 18 subjects were used in the Experiment II to determine the optimum map scale size. Finally, the implications of the findings may provide suggestions on designing safer and more efficient in-vehicle navigation systems.