In order to determine the relevant system boundary of transport related impact on the environment the assessment can be based on significant different aspects. Based on the ISO 14 025 applied by Product Category Rules NTM divides the system boundary in two dimensions. The x-axis describes the scope that determines the activities included. The y-axis determines the life cycle of each activity.

Figure 1. Principal for describing the system boundary of transport services

In order to describe the various aspects of the transport system the below figure may serve as an overview. This model is the foundation of describing the various scopes that can be included when assessing performance.

Figure 2. An overview of the transport system and its impact and interaction with society in general[1]

[1] Source Conlogic

The scope that is included default by NTM is well to wheel (wtw), but for specific purposes other scopes may of course be relevant. If electric and combustion engines are to be included or compared wtw is a minimum requirement.

Regarding the life cycle perspective, the scope to include default is operation of activity, i.e. core process (see below model), but for specific purposes other assessments may be relevant.

The NTM default scope corresponds in all major aspects to the European Standard EN 16258 “Methodology for calculation and declaration of energy consumption and GHG emissions of transport services (freight and passengers)”.

Below is the default system boundary described in a more specified model.

 Figure 3 The blue and yellow boxes show the NTM default definition of scope and life cycle assessment for assessment of the environmental impact of transport activities.

In a higher resolution the system boundary can be described as below.

Figure 4. Core process well to wheel, high resolution