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Automobile drivers have a tendency to make judgments of their perceived rate of travel, or egospeed, that are slower than the speed they are actually traveling. This often leads them to drive at faster speeds, which results in increased crash risk for themselves and other vehicles. A driver's egospeed can be affected by visual cues in the environment including Edge Rate (ER) optical effects. The purpose of this research was to examine how speed production would be affected by (1) the presence and distance of roadside (geographic) ER cues; (2) proximal ER cues such as traffic moving at faster, similar, or slower speeds than the driver; and (3) the combined presence of geographic and traffic ER cues. A novel methodology had participants drive at comfortable and ratio speeds while experiencing 10 continuous minutes of each ER condition. Performance was examined in terms of: mean speed choice; ratio speed-production performance (target ratio); speed consistency (speed drift ratio, reliability ratio); and judgments of task difficulty (ease rating). Data suggested that certain cues reduced a driver's comfortable speed of travel: the presence of geographic ER cues; closer-distance geographic ER cues; slower-speed-traffic ER cues; and the pairing of geographic ER with slower-speed-traffic ER cues. Data showed that a reduction in traffic speeds may be produced by increasing the saliency of ER cues in the environment regardless of traffic conditions.