A pendulum service is fairly flexible in terms of the selection of port calls, particularly on maritime ranges that have nearby and competing ports (e.g. North American East coast, Western Europe). This implies that a maritime container shipping company may opt to bypass one port to the advantage of another if its efficiency is not satisfactory and if its hinterland access is problematic. The shipping network consequently adapts to reflect changes in market conditions. The structure of pendulum service networks can take many shapes depending on factors such as the markets being serviced, trade imbalances and regulations: