We fit simultaneously the curves given by equation (4) in the interval [v0, vmax], with v0=17.9 km h−1 and vmax=130 km h−1 and for t=5, 10, 15, 20, …, 180 min (see Methods section). Each plot refers to a different trip durations (t=5, 15, 30, 60, 120, 180 min). The dots are the empirical data whereas the solid line is the fit obtained using equation (4). The best fit value of the parameters are p′=1.06 jumps per hour, δv′=20.9 km h−1 (and v0=17.9 km h−1). We therefore get δv≈40 km h−1 for the speed gap, in excellent agreement with the progression of the most common speed limits in Italy: 50 km h−1 (urban), 90 km h−1 (extra-urban) and 130 km h−1 (highways). These results suggest that a multilayer hierarchical transportation infrastructure can explain the constant acceleration observed in both public and private transportation.