Adjusting the priority of public transportation makes it possible to keep public transport systems functioning while maintaining standards of sustainability and economic efficiency. In many cities and urban areas bus - priority schemes have been realised through “simple” means. Due to the continuous increase of traffic, space limitations, and economic restrictions new and innovative solutions are required today and in the future in order to put the political will which is so often present into action.

The functional rules of public transportation, along with the demands on it, the possible malfunctions, and the assessment methods used are discussed. The bus system and its appropriate handling as an element of the whole system places two main requirements on bus-prioritising measures. 
1. Regular operation and therefore high reliability and 
2. Short, unimpaired travel.

Due to its considerably higher carrying capacity, priority should be given to public transportation for a short but critically chosen time. Of great importance is the finding that an unreliable service with theoretically short travel times is rated below one with longer travel times but assured arrival times (reliability, guaranteed transfers).

Disturbances which prevent smooth operation have a wide range of different causes and different impacts. Depending on the issue, individual interchanges, single routes, branches, or the entire network should be analysed. Assessment criteria are available for the analysis and preparation of schemes.