### abstract ###
people make systematic and predictable mistakes regarding estimations of average speed and journey time
in addition  people have been shown to commit a time-saving bias by underestimating the time that can be saved when increasing from a low speed and overestimating the time that can be saved when increasing from a relatively high speed
these misestimations have been shown to relate to biases in judgments of the speed required to arrive at a specific time and to choosing unduly high speed
professional drivers  such as taxi drivers  might be less susceptible to these biases due to their increased driving experience
in the current study  we interviewed taxi drivers about a journey they were currently making and examined their estimations of journey time  average speed and time savings
compared to a group of non-professional car drivers  taxi drivers showed the same considerable misestimations of driving speed  journey time and time savings as non-professionals
however  overestimations of time savings among taxi drivers were smaller than those made by car drivers
we discuss the practical significance of these findings
### introduction ###
estimating driving speed is not an easy task
research on mean speed estimation indicates that people make systematic errors in estimating average speed
for example  when judging the mean speed of a trip that included two parts  one with a higher speed and one with a lower speed  people overestimate the weight of the higher speed and underestimate the impact of the lower speed on the average speed of the entire trip  CITATION
for example  when drivers were asked to estimate the mean speed of a journey when it was possible to drive at a high speed e g    NUMBER  kph for most of the trip except for a limited part of the trip  where speed limit was significantly lower e g    NUMBER  kph  the mean speed of the entire route was overestimated  CITATION
in contrast to previous theoretical assertions that people assign equal weights to different speeds when estimating the mean speed of a trip  CITATION   these studies found that people actually assign different weights to different speeds  usually overweighting higher speeds and underweighting lower speeds  CITATION
