Interchange between services is an inescapable feature of urban public transport journeys. This almost inevitably introduces some walking and waiting time for the passenger, and there may be other negative aspects of the interchanges themselves. The proportion of journeys that involve interchange ranges from less than ten percent to more than fifty percent, according to the city. The promotion of urban public transport would benefit from improving the quality of interchanges - and this needs the dissemination of good practice on interchange design.