After that, the driving speed, i.e., , of next time zone t-l for road segment i can be estimated by the EWMA function[14], which is formulated in (8) where β is the weighting
factor and and denote the estimated and observed driving speeds of time zone t-1 for road segment i respectively. With the EWMA, the less weight is given to the driving speed of more ancient time zone and the higher weight to that of more recent one. Finally, the estimated driving speed of next time zone t for road segment i is recorded and used in the VBA* route planning algorithm.