An analytical model using the lognormal probability density function is applied to published driver response time measurements. Close agreement is obtained when this function is fitted to the measured responses of drivers to the onset of the amber signal as they approach signalized intersections. Statistical parameters associated with three sets of measured data are presented. Parametric estimates of 1.1 to 1.2 sec for the median, 1.3 to 1.4 sec for the mean, and 0.55 to 0.75 sec for the standard deviation of the distribution function appear to give the best fit to the experimental values.