Ways to improve the Texas Department of Transportation's (TxDOT's) current vehicle warning light policy were researched. Tasks included a survey of motorist perceptions of different warning light color combinations and also field studies of the effect of selected color combinations on traffic behavior. The motorist survey, conducted at driver licensing stations in Dallas-Fort Worth, San Antonio, and Houston, indicated that the combination of blue and amber lights implied a slightly greater sense of hazard to motorists than did the amber light alone. However, this greater sense of hazard did not necessarily translate into differences in how motorists believed they needed to respond. Field studies conducted at freeway locations in San Antonio and Houston investigated the effect of selected, alternative vehicle warning-light color combinations on vehicle speeds, lane choice, and braking activity. Researchers found significant reductions in speeds at a few sites--but not all--for the amber and blue warning light color combination when compared with speeds observed when only an amber warning light was used. In addition, the data suggested a trend toward increased brake usage for the red, amber, and blue light configuration compared with the amber-light-only configuration. There also was evidence that the amber-and-blue light configuration slightly increased the frequency of brake applications. Furthermore, the use of a law enforcement vehicle during testing resulted in significantly more brake-light activations than did a TxDOT courtesy patrol vehicle outfitted with the same warning light colors.