Fig. 4From: Travel time predictions: should one model speeds or travel times?Kernel density estimate for residuals of link travel times (a, c, e, g) and link speeds (b, d, f, h) for all links, all time-of-day-intervals on the validation set for Hietzing (a, b), Westbahnhof (c, d), Ring (e, f) and Südosttangente (g, h). Indirect method in blue, direct method in red. Estimated means are indicated as dash dotted lines, normal densities as broken linesBack to article page