Long Combination Vehicles (LCV) are transport efficient. However, allowing any combination of, individually legal, loaded vehicle units which when connected become LCV, can lead to traffic risks. Therefore, ways to assess LCVs are developed. The paper proposes an open tool which can assess a certain LCV for a certain load distribution. The tool could be a base for a digital service for such assessment. The assessment is done with Performance-Based Standards (PBS). PBS measures, computed through dynamic models and simulations, can be compared to numerical requirements. The vehicle parameters are selected to be as easy as possible to find values on, e.g., from available data in a vehicle unit registry. Also, the loading is defined by giving the static vertical force for each axle and the load height for each vehicle unit. A PBS based assessment method, as opposed to simply prescribing certain vehicle design parameters, would encourage novel combination vehicle designs. That would continuously drive the development towards even better transport efficiency, including energy efficiency.