《时间平均车速》PPT课件.ppt

3.2 Definition of Speed,Time mean speed(TMS，时间平均车速)-defined as the average speed of all vehicles passing a point on a highway over some specified time period Space mean speed(SMS，空间平均车速)-defined as the average speed of all vehicles occupying a given section of a highway over some specified time period,TMS is a point measure,while SMS is a measure relating to a length of highway or lane SMS is often used in traffic flow theory study at macroscopic level while TMS is used for engineering studyTMS SMS,Average travel speed and average running speed（平均行程，行驶速度)-Average travel speed=distance/travel timeAverage running speed=distance/running timeRunning time=travel time-stopped delays,Operating speed（运营速度）-defined as the maximum safe speed at which a vehicle can be conducted in a given traffic stream,without exceeding the design speed of the highway segment.Critical speed or Optimal speed(临界车速)-defined as the speed at which maximum flow rate(capacity 通行能力)can be achieved(or at which gas consumption of vehicles is at the lowest),Percentile speeds（百分位速度）-is a speed below which the stated percent of vehicles in the traffic stream travel,In traffic engineering,85th percentile speed is often used as a measure of the maximum reasonable speed for the traffic stream(upper limit),while the 15th percentile speed may be used as a measure of the minimum reasonable speed for the traffic stream.The 50th percentile or median speed is used to describe the midpoint of the speed distribution.,