In this paper, firstly, a new trial to solve the prediction problem in terms of the lower and higher order cumulants of noise level and the level probability distribution in the general form of statistical Laguerre expansion series is theoretically considered in connection with the internal structure of road traffic noise. More concretely, the above road traffic noise is considered on cases of the arbitrariness of the number of lanes on the road and types of vehicle, the ratio mixture of vehicle types, the average number and the acoustic power level distribution of vehicles running with proper mean velocities on the respective lane of the road, the length of straight interval on the road and the distance from the observation point. Next, the equivalence problem of replacing multilane of road and various types of vehicles with one specific lane and one type of vehicle is discussed in detail. The brief summary of our prediction theory is given below. The moment generating function for the total energy of random noise at an observation point emitted from various vehicles on the road can be derived as shown in Eq. (9) by taking the proper characteristic of noise on an additivity of their sound energy flux density into consideration. Especially in Eqs. (11) and (12) the expressions of lower and higher order cumulants distribution functions are expressed in the general form of statistical Laguerre expansion series (cf. Eqs. (14) and (17)) and the effect of internal structure on traffic noise as mentioned in the above is reflected concretely in two parameters m, S` and expansion coefficient of the above expression (cf. Eqs. (20) and (21)). The equivalent vehicle number in a case when multi-lanes of road are replaced by one specific lane in a sense of equivalence of nth cumulant (or NPL) is given by Eq. (25) (or Eq. (33)) and the equivalent acoustic power of vehicle in a case when various types of vehicles are replaced by one specific type of vehicle on an arbitrary lane in a sense of equivalence of nth culmulant is given by Eq. (26). The validity of the theoretical results is also supported experimentally by use of digital simulation technique.