Regarding traffic demand and road capacity as variables conforming to normal distribution,the different road network unblocked reliability can be gotten by the random experimentation,and the change rules of road network unblocked reliability and velocity under different supply and demand combination are put foreword.

On the basis of randomness analysis of traffic demand and supply and the reliability analysis of network,the concept of unblocked reliability was presented.

According to the travel characteristics and high efficiency requirement of emergency vehicles,the travel states of emergency vehicles are classified into five levels,then the concept of unblocked reliability of emergency vehicles is presented,and a multilevel fuzzy synthe.